University of Adelaide · Contents Abstract i Declaration iii Acknowledgements iv Abbreviations v...
Transcript of University of Adelaide · Contents Abstract i Declaration iii Acknowledgements iv Abbreviations v...
Department of Chemistry
New Methods for the Synthesis of Diynyl, Diyndiyl and Bis(diyndiyl)
Ruthenium(II) Complexes
A Thesis Submitted Towards the Degree of Doctor of Philosophy
By
Nancy Scoleri
B.Sc. (Hons)
July 2008
Contents
Abstract i
Declaration iii
Acknowledgements iv
Abbreviations v
General experimental conditions viii
CHAPTER ONE: Introduction
1.1. The syntheses of diynyl complexes 3
1.1.1. Synthetic strategy one 4
1.1.2. Synthetic strategy two 6
1.1.3. Synthetic strategy three 7
1.1.4. Synthetic strategy four 8
1.1.5. Alternative synthetic strategies 9
1.2. The syntheses of diyndiyl complexes 10
1.2.1. Symmetric diyndiyl complexes 11
1.2.1.1 Synthetic strategy one 12
1.2.1.2. Synthetic strategy two 14
1.2.1.3. Synthetic strategy three 17
1.2.1.4. Synthetic strategy four 18
1.2.2. Asymmetric diyndiyl complexes 19
1.3. The syntheses of trinuclear complexes 24
1.3.1. Organic linkers 24
1.3.2. Organometallic linkers 26
1.4. Molecular wires 30
1.4.1. Evaluation of molecular wires by cyclic voltammetry 33
1.5. Work described in this thesis 41
CHAPTER TWO: The Chemistry of Bis(Diyndiyl) Ruthenium(II) Complexes 2.1. Introduction 43
2.2. Aim of this work 47
2.3. Results and Discussion 48
2.3.1. Symmetric complexes trans-Ru{C4[Ru]}2(dppe)2 48
2.3.2. Asymmetric complexes trans-Ru{C4[Ru]}{C4H}(dppe)2 51
2.3.3. Asymmetric complexes trans-Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 54
2.3.4. Synthesis of trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 58
2.3.5. Gold reactions 60
2.3.5.1. Synthesis of trans-Ru{C4[Ru]}{C4[Au(PPh3)]}(dppe)2 62
2.3.5.2. Synthesis of trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-
dppm)(CO)7]}(dppe)2
65
2.3.6. Various reactions of trans-Ru(C4H)2(dppe)2 67
2.3.6.1. Reaction with AuCl(PPh3) 67
2.3.6.2. Reaction with Co3(µ3-CBr)(µ-dppm)(CO)7 68
2.3.6.3. Reaction with TCNE 69
2.3.7. Synthesis of trinuclear copper(I) and silver(I) alkynyl complexes 75
2.4. Electrochemistry 80
2.4.1. trans-Ru{C4[Ru]}2(dppe)2 complexes 80
2.4.2. trans-Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 complexes 85
2.4.3. trans-Ru{C4[Ru]}{C4H}(dppe)2 complexes 88
2.4.4. trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 89
2.4.5. Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 89
2.4.6. [{Cp*(dppe)Ru}(C≡C)2{M3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][X]
(M = Cu, Ag; X = PF6, BF4)
90
2.5. Conclusions 94
2.6. Experimental 96
CHAPTER THREE: A New Method for the Synthesis of Diyndiyl Ruthenium(II) Complexes
3.1. Introduction 107
3.2. Aim of this work 110
3.3. Results and Discussion 111
3.3.1. The lithiation of [Ru](C≡CC≡CH) ([Ru] = Ru(dppe)Cp*,
Ru(PPh3)2Cp)
111
3.3.1.1. Synthetic strategy 111
3.3.1.2. NMR study 112
3.3.2. Investigation of the formation of [Ru](C≡CC≡CLi) 113
3.3.2.1. Synthesis of [Ru](C≡CC≡CTMS) 113
3.3.2.2. Synthesis of [Ru]{C≡CC≡C[Au(PPh3)]} 116
3.3.3. Reactions of [Ru](C≡CC≡CLi) with various metal halides 118
3.3.3.1. Reaction with (AuCl)2(µ-dppm) 118
3.3.3.2. Reaction with cis-PtCl2(PPh3)2 121
3.3.3.3. Reactions with GeClPh3 and SnClPh3 121
3.3.3.4. Reaction with [CuCl(PPh3)]4 124
3.3.3.5. Reaction with RhCl(CO)(PPh3)2 128
3.4. Conclusions 131
3.5. Experimental 132
CHAPTER FOUR: The reactions of Ru(C≡CC≡CLi)(dppe)Cp*
4.1. Introduction 138
4.1.1. The reaction of nucleophilic complexes with organic reagents 138
4.1.2. The reaction of nucleophilic complexes with polyfluoroaromatic
reagents
139
4.1.3. The nucleophilic ruthenium(II) complex Ru(C≡CC≡CLi)(dppe)Cp* 140
4.2. Aim of this work 142
4.3. Results and Discussion 143
4.3.1. Reactions with organic reagents 143
4.3.1.1. Synthesis of Ru(C≡CC≡CMe)(dppe)Cp* 143
4.3.1.2. Synthesis of Ru{C≡CC≡CC(O)Ph}(dppe)Cp* 145
4.3.1.3. Synthesis of Ru{C≡CC≡CC(O)Me}(dppe)Cp* 146
4.3.1.4. Synthesis of Ru{C≡CC≡CC(O)OMe}(dppe)Cp* 147
4.3.1.5. Synthesis of {Ru(C≡CC≡C)(dppe)Cp*}2(CO)2 147
4.3.1.6. Synthesis of Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* 148
4.3.1.7. Reaction with TCNE 152
4.3.2. Reactions with polyfluoroaromatic reagents 158
4.3.2.1. Synthesis of Ru(C≡CC≡CC6F5)(dppe)Cp* 158
4.3.2.2. Synthesis of Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* 161
4.3.2.3. Synthesis of Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* 162
4.3.2.4. Synthesis of Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* 163
4.3.2.5. Synthesis of Ru(C≡CC≡CC10F7-2)(dppe)Cp* 165
4.3.2.6. Further reactions with Ru(C≡CC≡CC6F5)(dppe)Cp* 172
4.4. Electrochemistry 176
4.4.1. CV of products from the reactions with organic reagents 176
4.4.2. CV of products from the reactions with polyfluoroaromatic
reagents
177
4.5. Conclusions 181
4.6. Experimental 182
CHAPTER FIVE: Some Chemistry Involving Azide Reagents
5.1. Introduction 192
5.2. Aim of this work 199
5.3. Results and Discussion 200
5.3.1. Reactions of Ru(C≡CC≡CR)(dppe)Cp* (R = TMS, H, Au(PPh3)) 200
5.3.2. Reactions of Ru(C≡CC≡CH)(PPh3)2Cp 211
5.3.3. Reactions of Ru(C≡CH)(dppe)Cp* 212
5.4. Conclusions 215
5.5. Experimental 216
General conclusions 220
References 222
Complexes Index 231
i
Abstract
Chapter One outlines the different methods described in the literature for the synthesis
of diynyl, symmetric and asymmetric diyndiyl complexes. The extension to
complexes containing a central bridging group within the carbon chain is also
introduced with the description of two different linking groups, either an organic or
organometallic moiety. A brief overview of molecular electronics and one method of
evaluation of electronic communication, cyclic voltammetry, are also addressed.
Chapter Two describes the synthesis of novel symmetric and asymmetric
bis(diyndiyl) ruthenium(II) complexes of general formula {LnM}-C≡CC≡C-{M”L”p}-
C≡CC≡C-{M’L’m}, featuring two transition metal fragments linked by either a
Ru(dppe)2 moiety or a trinuclear copper(I) or silver(I) cluster M3(µ-dppm)3 (M = Cu,
Ag). Through the use of cyclic voltammetry, it was shown that the inclusion of these
three particular bridging groups allows electronic communication between the two
terminal end-groups. The chemistry of the starting material trans-Ru(C4H)2(dppe)2 (1)
is also described, forming novel complexes when reacted with AuCl(PPh3) or TCNE.
Chapter Three describes a new convenient synthetic route to diynyl and diyndiyl
ruthenium(II) complexes. Lithiation of the ruthenium(II) diynyl complexes
Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp with n-BuLi yields the
lithium complexes Ru(C≡CC≡CLi)(dppe)Cp* and Ru(C≡CC≡CLi)(PPh3)2Cp. The
most favorable conditions for their formation are examined by using NMR
spectroscopy and different assay reactions. These lithium species are further reacted
with a range of metal halides to give new asymmetric diyndiyl complexes of general
formula [Ru](C≡CC≡C){MLn} (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp).
ii
Chapter Four investigates the reactivity of the novel lithium complex
Ru(C≡CC≡CLi)(dppe)Cp* synthesised in Chapter Three. The nucleophilic nature of
this complex is assessed with a range of electrophiles such as organic substrates or
polyfluoroaromatic compounds. A number of new complexes are prepared and single-
crystal X-ray structure determinations are reported for many of the complexes. The
electrochemistry of some of these complexes is also described.
Chapter Five summarises the reactions of diynyl ruthenium(II) complexes
Ru(C≡CC≡CR)(dppe)Cp* (where R = H, TMS, Au(PPh3)) with three azide reagents
TMSN3, TsN3 and AuN3(PPh3). The reactions are suggested to undergo a Huisgen
1,3-alkyne-azide cycloaddition to generate 1,2,3-triazoles which further react to give
the various products. The complexes synthesised are characterised by spectroscopic
methods and, where possible, by X-ray structure determination. Furthermore, the
reactions of the complexes Ru(C≡CC≡CH)(PPh3)2Cp and Ru(C≡CH)(dppe)Cp* with
azides to give the ruthenium azido complexes [Ru]N3 (where [Ru] = Ru(PPh3)2Cp,
Ru(dppe)Cp*) are described.
iii
Declaration This thesis contains no material which has been accepted for the award of any other
degree or diploma in any university, and to the best of my knowledge, contains no
material previously published or written by another person except where due
reference has been made.
I give consent for this thesis to be made available for photocopying and loan if
applicable.
Nancy Scoleri Date: 4th of July 2008
iv
Acknowledgements
First, I would like to thank my supervisor, Professor Michael Bruce for giving me the
opportunity to work on an interesting and challenging project. It has been a unique
experience which I will always remember. I am also grateful for the help of my co-
supervisor Dr Marcus Cole throughout the past few years.
Thank you to Professor Allan White and Dr Brian Skelton for the X-ray structures,
Professor Brian Nicholson for the ES-MS and Dr. Simon Pike for valuable
discussions on NMR spectra and the organic side of my project. I would also like to
thank Professor Jean-François Halet and Dr Stéphane Rigaut for running the DFT
calculations and for their suggestions on the trinuclear project. Thanks also to Phil
Clements, Graham Bull and Peter Apoefis, staff members of our chemistry
department who have helped with instrument failures.
Special thanks to Prof. Michael Bruce, Dr Marcus Cole and Dr. Gary Perkins for
giving their time to read my thesis. Your corrections and advice were greatly
appreciated.
Thanks must go to everyone I have had the pleasure of sharing a lab with: Dr Maryka
Gaudio, Dr Natasha Zaitseva, Dr Cassandra Mitchell, Dr Shirley Xiao-Li Zhao, Dr
Benjamin Hall, Dr Gary Perkins, Dr David Armitt and Christian Parker. Thank you
also to Mable Fong, Renée Morelli, Suzanne Lochet and Alice Granger for their
friendship and for giving me distraction outside my PhD.
Finally, special and most important thanks must go to my family. I am grateful to my
parents for their ongoing encouragements, love and faith in me. I really appreciate
everything you have ever done for me. Thank you also to my brothers, Tony and
Gianny for being there when I needed you. Thank you also to Gary for your love and
support and keeping me focussed on achieving my goals.
v
Abbreviations
General:
° Degrees °C Degrees Celsius Å Ångstrom anal. Analysis Acac Acetylacetonate av. Average Bpy 2,2’-bipyridyl Bu Butyl ca Approximately
Calcd Calculated cm Centimetres Cp Cyclopentadienyl Cp* Pentamethylcyclopentadienyl Cy Cyclohexyl dbu 1,8-diazabicyclo[5.4.0]undec-7-ene DFT Density-functional theory dippe 1,2-bis(diisopropylphosphino)ethane dmpe 1,2-bis(dimethylphosphino)ethane dppe 1,2-bis(diphenylphosphino)ethane dppm Bis(diphenylphosphino)methane e- Electron EH Extended Hückel theory eq Equivalent ESR Electron spin resonance Et Ethyl, -CH2CH3 Et2O Diethyl ether EtOH Ethanol eV Electron volts Fc Ferrocenyl FMO Frontier molecular orbital g Gram h Hour(s) HOMO Highest occupied molecular orbital IR Infrared LDA Lithium Diisopropylamide, LiNPri
2 LUMO Lowest unoccupied molecular orbital Me Methyl, CH3
vi
MeLi Methyl lithium MeOH Methanol mg Milligrams min Minutes MLn General metal-ligand fragment mL Millilitres mm Millimetres mmol Millimoles NMR Nuclear magnetic resonance Na[BPh4] Sodium tetraphenylborate Na[PF6] Sodium hexafluorophosphate NaOMe Sodium methoxide [NBu4]F Tetrabutylammonium fluoride NHEt2 Diethylamine NEt3 Triethylamine OAc Acetate OTf Triflate, trifluoromethanesulfonate, CF3SO3
- ORTEP Oak Ridge Thermal Ellipsoid Plot program Pd(PPh3)4 Palladium(0)tetrakis(triphenylphosphine) ppn Bis(triphenylphosphine)iminium Ph Phenyl, -C6H5 PPh3 Triphenylphosphine Pz Pyrazole Tol Tolyl R General organic group [Ref] Reference r.t. Room temperature Rc Ruthenocenyl s Seconds tBu Tertiary butyl, -C(CH3)3 TCNE Tetracyanoethylene Temp. Temperature THF Tetrahydrofuran TLC Thin layer chromatography tmeda Tetramethylethylenediamine TMS Trimethylsilyl, -Si(CH3)3, SiMe3 Tp’ Hydridotris(3,5-dimethylpyrazolyl)borate Ts Tosyl ∆ Reflux µ Micro X Halide
vii
NMR: br Broad d Doublet dt Doublet of triplet Hz Hertz m Multiplet
nJIJ n bond coupling constant between nuclei I and J ppm Parts per million s Singlet sept Septet t Triplet δ Chemical shift COSY Correlation Spectroscopy IR: br Broad cm-1 Wavenumbers m Medium sh Shoulder w Weak s Strong Mass Spectroscopy: ES-MS Electrospray mass spectrum M Molecular ion m/z Mass per unit charge Electrochemistry: E Potential En Potential of nth redox process E1/2 Half-wave potential ∆E Potential difference ia Anodic peak current ic Cathodic peak current mV Millivolts V Volts CV Cyclic voltammogram
viii
General experimental conditions
All reactions were carried out under dry, high purity nitrogen or argon using standard
Schlenk techniques. Solvents were purified as follows: THF, Et2O, benzene were
distilled from Na/benzophenone; CH2Cl2 was distilled from CaH2; NEt3 was distilled
from KOH; MeOH was distilled from Mg/I2.
Elemental analyses were performed by the Chemical and Micro Analytical Services
(CMAS), Belmont, Victoria, Australia and by Campbell Microanalytical Laboratory,
Chemistry Department, University of Otago, Dunedin, New Zealand.
Chromatography was performed using basic alumina (0.05 - 0.15 mm, pH 9.5 ± 0.5,
Fluka) and silica gel (0.04 - 0.06mm, 230 - 400 mesh). Preparative TLC was carried
out on glass plates (20 x 20 cm) coated with silica (Merck 60 GF254, 0.5 mm thick).
Instrumentation
IR spectra were recorded on a Perkin Elmer Spectrum 1720X FT IR spectrometer
(4000 - 400 cm-1). Nujol mull spectra were collected from samples mounted between
NaCl discs. Solution spectra were obtained using a 0.5 mm path length solution cell
fitted with NaCl windows.
NMR spectra were recorded on either Bruker AM300WB or Varian Gemini 2000
spectrometers (1H at 300.13 MHz, 13C at 75.47 MHz, 19F at 564.24 MHz, 31P at
121.50 MHz). Samples were contained within 5 mm sample tubes. Chemical shifts (δ)
are reported in ppm, relative to an internal standard of tetramethylsilane (0 ppm) for 1H and 13C NMR spectra, an external standard of H3PO4 (0 ppm) for the 31P NMR
spectra and an external standard of C6F6 (164.9 ppm) for the 19F NMR spectra.
ix
Cyclic voltammograms were recorded using either a Maclab/400 supplied by AD
Instruments or a Princeton PAR model 263A potentiostat using a conventional three
electrode cell, using a platinum working electrode, platinum wire counter electrode
and a pseudo-reference electrode. Solutions were made up in CH2Cl2 using a 0.1 M
solution of [Bun4N][PF6] as the supporting electrolyte. All potentials were referenced
against an internal ferrocene standard, [FeCp2]/[FeCp2]+ = + 0.46 V. In all cases, the
current is proportional to the square root of the scan rate.
The ES-MS were recorded on either a VG platform 2 or a Finnigan LCQ
spectrometer. Methanol and acetonitrile solutions were directly infused into the
instrument, using a chemical aids to ionisation as required.
X-ray crystal structures were determined by Professor Allan White and Dr Brian
Skelton, University of Western Australia, Australia. Structural data were received in
CIF format and the ORTEP plots of individual molecules were generated using
Mercury 1.4.2 for windows, with non-essential hydrogen atoms removed for clarity.
Throughout this thesis, ORTEP plots adhere to the following colour scheme:
ruthenium in pink, carbon in grey, phosphorus in orange, hydrogen in pale yellow,
nitrogen in blue, germanium in purple, fluorine in bright green, oxygen in red and
sulfur in darker yellow.
Chapter One
Introduction
2
Carbon is the fourth most abundant chemical element in the universe by mass after
hydrogen, helium, and oxygen. Carbon is found in the sun, stars, comets, and in the
atmospheres of most planets. It exhibits remarkable properties and its different
allotropes include the hardest naturally occurring substance (diamond) and also one of
the softest substances (graphite) known (Figure 1). Moreover, it has a great affinity
for bonding with other small atoms, including other carbon atoms, and is capable of
forming multiple stable covalent bonds with such atoms.
Figure 1: Atomic arrangements of carbon in diamond and graphite
In 1982 the synthesis of a new polymorph of elemental carbon, known as carbyne,
was reported.1 Carbyne is a linear form of carbon, consisting entirely of sp-hybridised
carbon atoms. Carbyne can be represented by three different structures (Figure 2).
Two features alternating triple and single bonds (alkynyl or poly-yndiyl) with either
sp ((A)) or sp3 ((B)) carbon termini and a third consists solely of double bonds
(cumulenic) with sp2 carbon termini ((C)).2
C (C C) C
X
X
X
X
X
X
C (C C) C
X
X
X
X
C (C C) C XX m mm
(A) (B) (C) Figure 2: The different structures of carbyne
3
Furthermore, a new class of complexes containing chains of conjugated carbon triple
bonds capped by different transition metal centres has become of considerable
interest. The synthesis of complexes of the general formula {MLn}-(C≡C)m-{MLn},
where {MLn} represents a metal-ligand fragment has been investigated extensively.3
The carbon atoms associated with the triple bond are sp hybridised and the highly
reactive carbon units can be stabilised by using suitable organometallic building
blocks as end-capping groups. The one-dimensional units are also exceptional linking
ligands in that π-electron delocalisation over all carbons atoms in the chain enables
electron transfer between two transition metal centres to occur. Furthermore, the
bonding between the metal centre and the organic bridge is of σ-bonding nature. This
allows electronic communication between the metal end-groups through the carbon-
carbon triple bond(s). Hence, these carbon-rich bimetallic complexes are of interest
for applications in the fields of non-linear optics,4,5 molecular switches and sensors6-9
or liquid crystals.10,11 Currently, complexes of the general formula {LnM}-(C≡C)m-
{MLn} including carbon chains containing from two up to 28 carbon atoms joining
the two metal-ligand centres are known.3,12,13 The work described in this thesis
focuses on the synthesis of complexes containing a butadiyndiyl chain, that is an
unsaturated carbon chain containing four carbon atoms.
1.1. The syntheses of diynyl complexes
In 1957, the first complex containing a bridging C4 ligand was described,14 followed
by more detailed studies performed by Hagihara and co-workers in the 1970s.15 They
reported the reaction of NiCl(PPh3)Cp with buta-1,3-diyne in the presence of a
Grignard reagent which gave the diynyl complex Ni(C≡CC≡CH)(PPh3)Cp (Scheme
1).15
Cp(Ph3P)Ni C C C C H+ H C CC2H5MgBr
NiCl(PPh3)Cp H2
Scheme 1: The synthesis of Ni(C≡CC≡CH)(PPh3)Cp
4
Since then, many diynyl complexes of general formula {LnM}(C≡CC≡CR) (R =
TMS, H) were reported. They feature a C4 carbon chain capped by a metal-ligand
fragment at one end and a hydrogen atom or other simple organic group at the other.
The syntheses of diynyl complexes are of significant interest as these reagents are
very useful starting materials.
A range of diynyl complexes have been obtained from various synthetic routes. The
four most used methods are:
1) the Cu(I)-catalysed reaction of 1,3-diynes with metal-halide precursors
2) metal exchange with coupling of silyl and stannyl derivatives
3) the reaction of metal-halide precursors with organolithium reagents
4) the reaction of metal-halide with trimethylsilylbutadiyne in the presence of
Na[BPh4] and an amine solvent.
1.1.1. Synthetic strategy one
The most used method for the synthesis of diynyl complexes involves the Cu(I)-
catalysed reaction of 1,3-diynes with metal-halide precursors. This method was first
reported in 1977 for the synthesis of the cis- and trans- isomers of
Pt(C≡CC≡CH)2(PBu3)2.16,17 The mechanism of this reaction is considered to proceed
via a copper(I) alkynyl intermediate which undergoes an alkynyl-halide exchange
with the {LnM}X species and results in the formation of the diynyl complex and
regeneration of the CuX catalyst (Scheme 2).
5
RC C C CH
RC C C CCu
RC C C C{MLn}
HI (HX)
CuI (CuX)
{MLn}X
Scheme 2: Catalytic cycle for the synthesis of diynyl complexes
Many examples of this synthetic route have been reported in the literature. For
instance, the reaction of WCl(CO)3Cp with trimethylsilylbutadiyne gave the diynyl
W(C≡CC≡CTMS)(CO)3Cp in 85% yield (Scheme 3).18
Cp(OC)3W C C C C TMS+W(CO)3CpClCuI
THF/NHEt2H C C TMS
2
Scheme 3: The synthesis of W(C≡CC≡CTMS)(CO)3Cp
Similarly, the reaction of {MLn}Cl (where MLn = W(CO)3Cp’, Mo(CO)3Cp and
Fe(CO)2Cp; Cp’ = Cp or Cp*) with buta-1,3-diyne in the presence of CuI with
diethylamine as solvent gave the yellow diynyl complexes {MLn}(C≡CC≡CH) in
good yield (Scheme 4).19-21
{LnM} C C C C HH C C H+CuI
{MLn}ClTHF/NHEt2
{MLn} = W(CO)3Cp (90%) W(CO)3Cp* (77%) Mo(CO)3Cp (60%) Fe(CO)2Cp (32%)
2
Scheme 4: Synthesis of {MLn}(C≡CC≡CH)
6
1.1.2. Synthetic strategy two
Another method for the synthesis of diynyl complexes is the reaction of silyl and
stannyl derivatives (e.g. TMSC≡CC≡CTMS, Ph3SnC≡CC≡CTMS) with a metal
halide. 1,4-Bis(trimethylsilyl)buta-1,3-diyne, TMSC≡CC≡CTMS, has proved to be a
useful compound in the synthesis of diynyl complexes. For example, the reaction of
ReCl(CO)3(tBu2bpy) with TMSC≡CC≡CTMS in the presence of KF and AgOTf gave
Re(C≡CC≡CTMS)(CO)3(tBu2bpy) (Scheme 5).22
Re C C C C TMS+ TMS C CReCl(CO)2(tBu2bpy)KF, AgOTf
MeOH, ∆TMS2 (bpytBu2)(OC)2
Scheme 5: The synthesis of Re(C≡CC≡CTMS)(CO)3(tBu2bpy)
The diynyl complex Rh(C≡CC≡CTMS)(CO)(PPri3)2 was obtained from the treatment
of trans-Rh(OH)(CO)(PPri3)2 with the mixed silyl-stannyl diyne Ph3SnC≡CC≡CTMS
in benzene (Scheme 6).23
+ Ph3Sn C Ctrans-Rh(OH)(CO)(PPri3)2
Benzene
80oCTMS2 (PPri
3)2(CO)Rh C C TMS2
Scheme 6: Synthesis of Rh(C≡CC≡CTMS)(CO)(PPri
3)2
Similarly, the unsymmetric diyne Me3SnC≡CC≡CTMS was reacted with
PtCl2{P(tol)3}2 in THF to afford the diynyl complex Pt(C≡CC≡CTMS)Cl{P(tol)3}2 in
63% yield. Pt(C≡CC≡CTMS)Cl{P(tol)3}2 is further desilylated using [NBu4]F to give
the complex Pt(C≡CC≡CH)Cl{P(tol)3}2 (Scheme 7).24
Pt C C C C TMS
P(tol)3
P(tol)3
Cl
Pt C C C C H
P(tol)3
P(tol)3
Cl
Me3Sn C C TMS+THF
∆
THF
PtCl2{P(tol)3}2 2
[NBu4]F
Scheme 7: Synthesis of Pt(C≡CC≡CH)Cl{P(tol)3}2
7
1.1.3. Synthetic strategy three
A third method for the preparation of diynyl complexes involves the reaction of a
metal-halide precursor {MLn}X with an organolithium reagent such as
LiC≡CC≡CTMS. LiC≡CC≡CTMS is obtained from the treatment of
TMSC≡CC≡CTMS with one equivalent of methyllithium.25 The precipitation of the
lithium halide LiX drives the reaction to completion (Scheme 8).
{LnM} C C C C TMS+{MLn}X- LiX
Li C C TMS2
Scheme 8: Synthetic strategy three The synthesis of the complexes Fe(C≡CC≡CTMS)(CO)2Cp’ (where Cp’ = Cp, Cp*) is
an example of this route.26,27 These diynyl complexes contain a TMS-protected ligand
which can be further desilylated using potassium fluoride (Scheme 9).28
IFe
OC CO
RR
RR
RC C C CFe
OC CO
RR
RR
RTMS+
THF
R = H or Me
MeOH/THFKF
C C C CFe
OC CO
RR
RR
RH
-80oCLi C C TMS2
Scheme 9: The synthesis of Fe(C≡CC≡CH)(CO)2Cp’ (Cp’ = Cp, Cp*)
Similarly, the reaction of RuCl2(CO)2(PEt3)2 with LiC≡CC≡CTMS at -78oC afforded
the trans-bis(diynyl) complex Ru(C≡CC≡CTMS)2(CO)2(PEt3)2 which can then be
treated with [NBu4]F to give the complex Ru(C≡CC≡CH)2(CO)2(PEt3)2 (Scheme
10).25
8
Li C C TMS+ C CC C(Et3P)2(OC)2Ru TMSTHF
-78oCRuCl2(CO)2(PEt3)2 2
THF [NBu4]F
C CC C(Et3P)2(OC)2Ru H 2
25oC
2
Scheme 10: Synthesis of Ru(C≡CC≡CTMS)2(CO)2(PEt3)2 and Ru(C≡CC≡CH)2(CO)2(PEt3)2
1.1.4. Synthetic strategy four
The reaction of a metal halide with the mono TMS-substituted starting material
trimethylsilylbutadiyne HC≡CC≡CTMS in the presence of Na[BPh4] in an amine
solvent was described as another method for the synthesis of diynyl complexes. For
example, treatment of FeCl(dppe)Cp* with HC≡CC≡CTMS gave the diynyl
Fe(C≡CC≡CTMS)(dppe)Cp* in 82% yield.29 The presence of the non-coordinating
salt Na[BPh4] facilitates the ionisation of the Fe-Cl bond and NEt3 leads to
deprotonation of the intermediate to give the desired complex. The analogous
ruthenium diynyl complexes were also synthesised in very good yields using this
method (Scheme 11).30
+ C CC C{LnM} TMSTHF/NEt3
{LnM} ClNa[BPh4]
{MLn} = Fe(dppe)Cp* (82%) Ru(dppe)Cp* (79%) Ru(PPh3)2Cp (94%)
H C C TMS2
Scheme 11: Synthesis of {MLn}(C≡CC≡CTMS)
Furthermore, proto-desilylation of the two complexes Ru(C≡CC≡CTMS)(dppe)Cp*
and Ru(C≡CC≡CTMS)(PPh3)2Cp with [NBu4]F gave the unsubstituted buta-1,3-diyn-
1-yl complexes Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp,
respectively (Scheme 12).30
9
C CC C[Ru] HTHF
C CC C[Ru] TMS[NBu4]F
[Ru] = Ru(dppe)Cp* (96%) Ru(PPh3)2Cp (74%)
Scheme 12: The synthesis of diynyl [Ru](C≡CC≡CH) complexes
1.1.5. Alternative synthetic strategies
A few alternative methods have also been described in the literature when the
previous routes were unsucessful. The diynyl Fe(C≡CC≡CTMS)(dppe)Cp* was
synthesised by photolysis of Fe(C≡CC≡CTMS)(CO)2Cp* in the presence of dppe
(Scheme 13).28 The two carbonyl groups were substituted by the dppe ligand in this
case. It must be noted that this method is less efficient than the previously described
route (See Section 1.1.4.), Fe(C≡CC≡CTMS)(dppe)Cp* was obtained in 40% yield.
C C C CFe
Ph2P PPh2
TMShv
dppeC C C CFe
OC CO
TMS
Scheme 13: Synthesis of Fe(C≡CC≡CTMS)(dppe)Cp* The synthesis of Re(C≡CC≡CTMS)(NO)(PPh3)Cp* is an example of an alternative
route for the synthesis of diynyl complexes.20 It involves the reaction of the labile
precursor [Re(ClC6H5)(NO)(PPh3)Cp*]+ with HC≡CC≡CTMS, giving the
intermediate [Re(HC≡CC≡CTMS)(NO)(PPh3)Cp*]+ which is then deprotonated with
KOtBu to give the desired complex in 96% yield (Scheme 14).22
10
Re
+
NOPh3PCl
+
H C C TMS2
Re
ONPh3P
ReNOPh3P
KOBut
CCCCH TMS
C C C C TMS
Scheme 14: Synthesis of Re(C≡CC≡CTMS)(NO)(PPh3)Cp*
1.2. The syntheses of diyndiyl complexes
Diyndiyl complexes of general formula {LnM}-C≡CC≡C-{M’L’n’} are composed of
two metal-ligand fragments linked by a butadiyndiyl C4 chain.7 Complexes of this
type can be represented by one of three possible valence structures below (Figure 3).3
Most of the bimetallic complexes are represented by the valence structure A, which
comprises alternating single and triple bonds. Structure B is also based on polyynes,
while C shows a fully double-bonded cumulenic system.
{LnM} C C C C {MLn}
(A) (B)
(C)
{LnM} C C C C {MLn}
{LnM} C C C C {MLn}
Figure 3: Valence structures of diyndiyl complexes
11
The syntheses of bimetallic complexes bridged by diyndiyl ligands have been of
interest in recent times due to their potential applications in material science. Such
complexes have been suggested as components for non-linear optics,4,5 liquid
crystalline devices10,11 and as precursors to one-dimensional molecular wires.6-9
Studies have been concentrated on the synthesis of complexes containing C4 chains
capped at each end by two identical or different MLn groups.31 Although many
examples of symmetric compounds have been described only a few examples of
asymmetric complexes have been prepared.31
1.2.1. Symmetric diyndiyl complexes
Generally symmetrical diyndiyl complexes of the general formula {LnM}-C≡CC≡C-
{MLn} have been prepared by one of four main synthetic methods:
1) Coupling between an organic C4 unit with two equivalents of a metal-ligand
fragment
2) Homo-coupling between two metal ethynyl complexes {LnM}(C≡CH)
3) Coupling of a monometallic diynyl complex {MLn}(C≡CC≡CR) with a single
equivalent of a metal-ligand fragment.
4) Modification of the ligand configuration in an existing diyndiyl complex
C C=
Metal-ligand fragment {MLn}=
Halide=XR = Non-metallic substitution
+ RRX21)
22)
3)
4)
+R X
Metal-ligand fragment {M'Ln'}=
Scheme 15: Synthetic strategies for symmetric diyndiyl complexes
12
Outlined below are some literature examples demonstrating these strategies and the
reaction conditions that have been used to prepare symmetric diyndiyl complexes.
1.2.1.1 Synthetic strategy one
The first method for the synthesis of symmetric diyndiyl complexes involves the
coupling between an organic C4 unit with two equivalents of a metal-ligand fragment.
This is the most frequently used synthetic method due to the large number of
accessible butadiynyl-based starting materials and the wide range of coupling
conditions that can be applied.
Buta-1,3-diyne (HC≡CC≡CH) is the simplest and most reactive diyne molecule. It can
be prepared from the reaction of 1,4-chlorobut-2-yne with concentrated aqueous
potassium hydroxide and trapped in a THF solution.32 This compound tends to
polymerise but it can be stored in solution for up to one week at low temperatures (<
-20oC). Although buta-1,3-diyne must be handled with care, it has been used to
synthesise a number of diyndiyl complexes.
For example, the reaction of {RhCl(PPri3)2}2 or {IrCl(PPri
3)2}2 with buta-1,3-diyne in
hexane at -78°C gave the diyndiyl complexes {(PPri3)2Cl(H)Rh}2(µ-C≡CC≡C) and
{(PPri3)2Cl(H)Ir}2(µ-C≡CC≡C) in 68% yield33 and 85% yield,34 respectively (Scheme
16).
+ M C C C C M-78oC
2 {MCl(PPri3)2}2
M = Rh, Ir
Hexane
H
Cl Cl
H
Pri3P Pri
3P
PPri3 PPri
3
H C C H2
Scheme 16: {(PPri3)2Cl(H)Rh}2(µ-C≡CC≡C) and {(PPri
3)2Cl(H)Ir}2(µ-C≡CC≡C)
1,4-Bis(trimethylsilyl)butadiyne (TMSC≡CC≡CTMS) is a much more stable
derivative of buta-1,3-diyne. This white crystalline solid can be prepared in large
quantities by the oxidative coupling of trimethylsilylacetylene TMSC≡CH under Hay
coupling conditions (CuCl/tmeda/O2) and stored at room temperature.35 It has been
13
used in the preparation of a number of symmetric diyndiyl complexes. For instance,
the treatment of TMSC≡CC≡CTMS with an excess of RuCl(PPh3)2Cp in refluxing
methanol in the presence of KF yielded the desired symmetric complex
{Ru(PPh3)2Cp}2(µ-C≡CC≡C) in 66% yield (Scheme 17).36
TMS C C TMSRu
Ph3P PPh3
Cl +2 C CRu
Ph3P PPh3
C Ru
PPh3Ph3P
C
MeOHKF
∆2
Scheme 17: Synthesis of {Cp(PPh3)2Ru}2(µ-C≡CC≡C)
Similar chemistry occurs with TMSC≡CC≡CTMS and two equivalents of
Rh(OH)(CO)(PPri3)2 to give {Rh(CO)(PPri
3)2}2(µ-C≡CC≡C) in 75% yield (Scheme
18).23
+ Rh C C C C Rh2 Rh(OH)(CO)(PPri3)2 OC CO
Pri3P Pri
3P
PPri3
PPri3
MeOH
∆TMS C C TMS2
Scheme 18: Synthesis of {Rh(CO)(PPri3)2}2(µ-C≡CC≡C)
The gold diyndiyl complexes {Au(PCy3)}2(µ-C≡CC≡C) and {Au[P(tol)3)]}2(µ-
C≡CC≡C) are also prepared by treatment of AuCl(PCy3)37 or AuCl{P(tol)3}38 with
TMSC≡CC≡CTMS in presence of NaOH in a methanol solution (Scheme 19).
+ (R3P)Au C C C C Au(PR3)2 AuCl(PR3)MeOH
NaOHR = Cy or tol
TMS C C TMS2
Scheme 19: Synthesis of {Au(PCy3)}2(µ-C≡CC≡C) and {Au[P(tol)3]}2(µ-C≡CC≡C)
Furthermore, the dilithio derivative of buta-1,3-diyne (LiC≡CC≡CLi) was also used to
prepare diyndiyl complexes. This compound can be synthesised by various routes
such as the addition of n-BuLi to solutions of buta-1,3-diyne or cis-
HC≡CCH=CH(OMe) at low temperatures39,40 or the treatment of TMSC≡CC≡CTMS
14
with an excess of MeLi.41 The reaction of LiC≡CC≡CLi with two equivalents of
FeCl(CO)2Cp gives the corresponding diiron diyndyl complex {Fe(CO)2Cp}2(µ-
C≡CC≡C) with elimination of lithium chloride (Scheme 20).15
FeOC
CO
Cl +2 C CFeOC
CO
C FeCTHF
-25oC
COCO
Li C C Li2
Scheme 20: Synthesis of {Fe(CO)2Cp}2(µ-C≡CC≡C)
The complex {Fe(CO)2Cp}2(µ-C≡CC≡C) can also be synthesised by a method
involving the reaction of the organostannane Me3SnC≡CC≡CSnMe3 (prepared from
the reaction of LiC≡CC≡CLi with SnClMe3) with two equivalents of FeI(CO)2Cp in
the presence of PdCl2(NCMe)2 (Scheme 21).42
FeOC
CO
I +2 C CFeOC
CO
C FeCCO
CO
Me3Sn C C SnMe32PdCl2(NCMe)2
Scheme 21: Second method for the synthesis of {Fe(CO)2Cp}2(µ-C≡CC≡C)
1.2.1.2. Synthetic strategy two
A number of symmetric diyndiyl complexes have been obtained by homo-coupling of
two metal ethynyl complexes {LnM}(C≡CH). For example, Glaser oxidative coupling
conditions [Cu(OAc)2/pyridine/O2] were used to prepare the rhenium diyndiyl
complexes {Re(NO)(PR3)Cp*}2(µ-C≡CC≡C) (R = Ph,43-45 tol,8 C6H4tBu-48) from the
rhenium ethynyls Re(C≡CH)(NO)(PR3)Cp*. Pyridine acts as a base to deprotonate the
bis(vinylidene) obtained in situ (Scheme 22).
15
Re
ON PR3
C CH ON PR3
C
Re
NOR3P
CC
H
H
pyridine
Re
ON PR3
C C Re
NOR3P
CC
2+
Cu(OAc)2
R = Ph, tol, C6H4tBu-4
80oC CRe
Scheme 22: Synthesis of {Re(NO)(PR3)Cp*}2(µ-C≡CC≡C) (R = Ph, tol, C6H4
tBu-4)
However, it was found that these conditions are often too harsh for other complexes.
Thus, alternative reaction conditions were applied in order to synthesise other
diyndiyl complexes. The oxidative coupling of the ethynyls M(C≡CH)(dppe)Cp* (M
= Fe, Ru, Os) at low temperature with [FeCp2][PF6] generates a 17-electron radical
that undergoes a spontaneous carbon-carbon bond formation to afford an intermediate
bis(vinylidene) [{M(dppe)Cp*}2(µ-C=CH-CH=C)]2+. Deprotonation of the
bis(vinylidene) with KOtBu yields the desired symmetric diyndiyls
{M(dppe)Cp*}2(µ-C≡CC≡C) (M = Fe,46 Ru,47 Os48) in good yields (Scheme 23).
16
M
Ph2P PPh2
C CH[FeCp2][PF6]
CH2Cl2
M
Ph2P PPh2
C C
M
PPh2Ph2P
CC
H
H
2+
KOtBu THF
M
Ph2P PPh2
C C M
PPh2Ph2P
CC
M
Ph2P PPh2
C CH M
PPh2Ph2P
CHC
-80oC
M = Fe (92%), Ru (90%), Os (66%)
Scheme 23: Synthesis of {M(dppe)2 Cp*}(µ-C≡CC≡C) (M = Fe, Ru, Os)
The manganese diyndiyl [{Mn(dmpe)2(C≡CH)}2(C≡CC≡C)]+ was prepared in a
similar manner. Desilylation and subsequent deprotonation of
[Mn(dmpe)2(C≡CTMS)2]+ gave the radical complex Mn(dmpe)2(C≡CH)(C≡C.). This
radical undergoes a spontaneous homo-coupling reaction to give
[{Mn(dmpe)2(C≡CH)}2(C≡CC≡C)], which is oxidised by [Mn(dmpe)2(C≡CH)2]+
present in solution to afford [{Mn(dmpe)2(C≡CH)}2(C≡CC≡C)]+ in 65% yield
(Scheme 24).49
17
TMS C C Mn C C TMS
Me2P
Me2P
PMe2
PMe2
[NBu4]FHC C Mn C CH
Me2P
Me2P
PMe2
PMe2
+ - H+
H C C Mn C C
Me2P
Me2P
PMe2
PMe2
C C Mn C CH
Me2P
Me2P
PMe2
PMe2
HC C Mn C C
Me2P
Me2P
PMe2
PMe2
C C Mn C CH
Me2P
Me2P
PMe2
PMe2
HC C Mn C C
Me2P
Me2P
PMe2
PMe2
-e-
+
Scheme 24: Synthesis of [{Mn(dmpe)2(C≡CH)}2(C≡CC≡C)]+
1.2.1.3. Synthetic strategy three
A third useful method for the synthesis of diyndiyl complexes involves the coupling
of a monometallic diynyl complex {MLn}(C≡CC≡CR) with a single equivalent of a
metal-ligand fragment. This synthetic strategy uses complexes that already contain the
butadiyndiyl chain and various conditions were reported.
The first example is the synthesis of the iron diyndiyl {Fe(dippe)Cp*}2(µ-C≡CC≡C)
from the reaction of Fe(C≡CC≡CH)(dippe)Cp* with one equivalent of
FeCl(dippe)Cp* in the presence of K[PF6] and KOtBu (Scheme 25).50
C C C CFe
Pri2P PPri
2
HK[PF6]/KOtBu
MeOH/THF
C C C CFe
Pri2P PPri
2
FeCl(dippe)Cp*Fe
PPri2Pri
2P
Scheme 25: Synthesis of {Fe(dippe)Cp*}2(µ-C≡CC≡C)
18
Alternative coupling conditions were used for the synthesis of tungsten diyndiyl
complexes. Treatment of W(C≡CC≡CH)(CO)3Cp’ with WCl(CO)3Cp’ (where Cp’ =
Cp and Cp*) in the presence of copper iodide and diethylamine gave the complexes
{W(CO)3Cp’}2(µ-C≡CC≡C) in good yield.19,21 Similarly, the reaction of
Fe(C≡CC≡CH)(CO)2Cp* with FeCl(CO)2Cp* in the presence of copper iodide and
NEt3 gave the symmetric diyndiyl {Fe(CO)2Cp*}2(µ-C≡CC≡C) (Scheme 26).26
C CC C{LnM} HCuI/NHEt2
C CC C {MLn}{LnM}{MLn}Cl
{MLn} = W(CO)3Cp (80%) W(CO)3Cp* (90%) Fe(CO)2Cp* (85%)
Scheme 26: Synthesis of {MLn}2(µ-C≡CC≡C)
1.2.1.4. Synthetic strategy four
This synthetic strategy involves the modification of the ligand configuration in an
existing diyndiyl complex. The diyndiyl {Ru(PPh3)2Cp}2(µ-C≡CC≡C) was heated
under reflux in toluene with an excess of PMe3 to afford the mixed phosphine
complex {Ru(PPh3)(PMe3)Cp}2(µ-C≡CC≡C) in 43% yield.7 Similarly, the diyndiyl
complex {Ru(PPh3)2Cp)2(µ-C≡CC≡C) undergoes a ligand exchange in the presence
of dppe at elevated temperature to give the complex{Ru(dppe)Cp}2(µ-C≡CC≡C) in
86% yield (Scheme 27).30
C C C CRuPh2P PPh2
RuPPh2
Ph2P
TolueneC C C CRu
Ph3PPPh3
RuPPh3
PPh3
C C C CRu
Ph3PPMe3
RuPPh3
PMe3PMe3
dppeToluene
Scheme 27: {Ru(PPh3)(PMe3)Cp}2(µ-C≡CC≡C) and {Ru(dppe)Cp}2(µ-C≡CC≡C)
19
1.2.2. Asymmetric diyndiyl complexes
Asymmetric diyndiyl complexes of general formula {LnM}-C≡CC≡C-{M’L’n’} are
composed of two different metal-ligand fragments linked by a butadiyndiyl C4
chain.31 Only a few examples of asymmetric complexes have been prepared. This can
be explained as most symmetric diyndiyl complexes can be prepared in a single-step
reaction while asymmetric diyndiyl complexes require multi-step syntheses.
Generally, asymmetric diyndiyls can be prepared by one main synthetic route. It
involves the initial preparation of a diynyl complex of the general formula
{LnM}(C≡CC≡CR) where R is a hydrogen atom or other simple organic group such
as TMS. The terminal R group of the carbon chain is then substituted with another
metal-ligand fragment under various reaction conditions. Detailed below are some
literature examples that demonstrate the different reaction conditions that have been
used to prepare a range of asymmetric diyndiyl complexes.
First, asymmetric diyndiyl complexes have been synthesised using the CuI-catalysed
coupling of a diynyl complex with a metal halide in amine solvents. For example, the
reaction of W(C≡CC≡CH)(CO)3Cp with various metal halides gave the desired
asymmetric diyndiyl {W(CO)3Cp}(C≡CC≡C){MLn} in good yields (Scheme 28).31
C C C CW
OCCO
HCuI/NHEt2
C C C C {MLn}{MLn}Cl
OC
{MLn} = Mo(CO)3Cp (95%) = Fe(CO)2Cp (65%) = Ru(CO)2Cp (51%) = Rh(CO)(PPh3)2 (74%) = Ir(CO)(PPh3)2 (82%) = Au(PPh3) (97%)
W
OCCO
OC
Scheme 28: The synthesis of various asymmetric diyndiyl {W(CO)3Cp}(C≡CC≡C){MLn}
20
Furthermore, an alternative reaction involves the lithiation of the terminal diynyl
ligand of the complex {LnM}(C≡CC≡CH) with any of a range of organolithium bases,
such as n-, sec- or t-BuLi, or LDA, followed by treatment with a metal halide. The
lithiation of a terminal diynyl complex with a lithium base results in the formation of
a nucleophilic species {LnM}(C≡CC≡CLi) which is subsequently treated with the
metal halide to afford the desired diyndiyl complex (see also Chapter Three).
In 1990, Wong reported the deprotonation of terminal iron diynyl complexes
Fe(C≡CC≡CH)(CO)LCp (L = CO, PPh3) with sec-BuLi and the resulting anions were
trapped with {MLn}Cl to form {Fe(CO)LCp}(C≡CC≡C){MLn} (M = Fe, Mo, W; L =
CO, PPh3; Ln = (CO)2Cp, (CO)3Cp) (Scheme 29).27
C C C C HFe
OC L
C C C C LiFe
OC L
C C C CFe
OC L
Sec-BuLi
-78oC
Fe
COOC
L = CO, PPh3FeCl(CO)2Cp
C C C CFe
OC L
M
OC CO CO
MCl(CO)3Cp
M = Mo, W
Scheme 29: Wong’s methodology for the synthesis of diyndiyl complexes
A few years later, Gladysz and co-workers extended this work to the lithiation of the
diynyl complex Re(C≡CC≡CH)(PPh3)(NO)Cp*.22 The lithiated complex
Re(C≡CC≡CLi)(PPh3)(NO)Cp* was generated and then reacted with trans-
PdCl2(PEt3)2 to give {Re(PPh3)(NO)Cp*}(C≡CC≡C){PdCl(PEt3)2} or with trans-
RhCl(PPh3)2(CO) to give {Re(PPh3)(NO)Cp*}(C≡CC≡C){Rh(PPh3)2(CO)} (Scheme
30).
21
C CRe
ON PPh3-80oC
n-BuLi
PdCl2(PEt3)2 RhCl(PPh3)2(CO)
C C H C CRe
ON PPh3
C C Li
C CRe
ON PPh3
C C Pd
PEt3
PEt3
Cl C CRe
ON PPh3
C C Rh
PPh3
PPh3
CO
Scheme 30: The reactions of Re(C≡CC≡CH)(PPh3)(NO)Cp* The complex W(C≡CC≡CH)(CO)3Cp was lithiated with LDA at -78oC. The resulting
W(C≡CC≡CLi)(CO)3Cp was then reacted with MnI(CO)5 to give the asymmetric
complex {W(CO)3Cp}(C≡CC≡C){Mn(CO)5} (Scheme 31).31
C CW
OC -78oC
LDAC C H C C C C Li
CO CO
W
OC CO CO
C C C C Mn(CO)5W
OC CO CO
MnI(CO)5
Scheme 31: The synthesis of {W(CO)3Cp}(C≡CC≡C){Mn(CO)5}
Another reaction that can be used for the synthesis of asymmetric complexes involves
the complexation of the diynyl with the metal halide in the presence of both Na[BPh4]
and NEt3/dbu. For example, the heterometallic complex
{Ru(dppe)Cp*}(C≡CC≡C){Fe(dppe)Cp*} was obtained from the reaction of the
complex Ru(C≡CC≡CH)(dppe)Cp* with FeCl(dppe)Cp* (Scheme 32).51
22
C C C C HRu
Ph2P PPh2
FeCl(dppe)Cp*C C CRu
Ph2P PPh2
Fe
PPh2Ph2P
CNa[BPh4]
NEt3/dbu
Scheme 32: The synthesis of {Ru(dppe)Cp*}(C≡CC≡C){Fe(dppe)Cp*}
Some asymmetric complexes containing gold were also synthesised from the reaction
of diynyl complexes with AuCl(PR3) in the presence of K[N(TMS)2]. For example,
the complexes {Ru(L2)Cp’}(C≡CC≡C){Au(PR3)} (Cp’ = Cp, L = PPh3, R = Ph; Cp’
= Cp*, L2 = dppe, R = Ph, tol) were obtained in good yields (Scheme 33).30
C C HCp'(L2)Ru Au(PR3)CC C CCp'(L2)RuAuCl(PR3)
K[N(TMS)2]THF
Cp' = Cp, L = PPh3, R = Ph orCp' = Cp*, L2 = dppe, R = Ph, tol
2
Scheme 33: Synthesis of asymmetric diyndiyls {Ru(L2)Cp’}(C≡CC≡C){Au(PR3)} Furthermore, the TMS-protected diynyl can be used to synthesise several asymmetric
diyndiyl complexes. For example, the complex W(C≡CC≡CTMS)(CO)3Cp reacts
with RuCl(PPh3)2Cp in presence of KF and dbu to afford the asymmetric complex
{W(CO)3Cp}(C≡CC≡C){Ru(PPh3)2Cp} in 61% yield (Scheme 34).18
C CWOC KF/dbu
RuCl(PPh3)2CpC C TMS
OC CO
C C C CWOC
OC COMeOH
Ru
PPh3PPh3
Scheme 34: Synthesis of {W(CO)3Cp}(C≡CC≡C){Ru(PPh3)2Cp} Similarly, the reaction of Ru(C≡CC≡CTMS)(PPh3)2Cp with RuCl(dppe)Cp’ (where
Cp’ = Cp or Cp*) in MeOH, in the presence of KF and dbu, gave the complexes
{Ru(PPh3)2Cp}(C≡CC≡C){Ru(dppe)Cp’} (where Cp’ = Cp or Cp*) in 42% and 45%
yield, respectively (Scheme 35).30
23
C CKF/dbu
RuCl(dppe)Cp'C C TMS C C C C
MeOH
Ru
Ph3PPPh3
Ru
Ph3PPPh3
RuPPh2Ph2P
RR
RR
R
R = H, Me
Scheme 35: Synthesis of {Ru(PPh3)2Cp}(C≡CC≡C){Ru(dppe)Cp’}
The mixed-metal complex Ru(C≡CC≡CFc)(dppe)Cp was obtained from the reaction
between FcC≡CC≡CTMS and RuCl(dppe)Cp in the presence of KF and dbu while the
complex Ru(C≡CC≡CFc)(dppm)Cp was synthesised from a similar reaction but in
presence of K[PF6] instead (Scheme 36).52
C CKF or K[PF6]
C CC C Fc
MeOH
TMS
n = 1, 2
RuPh2P PPh2
(CH2)n
FcRuPh2P PPh2
(CH2)n
Cl+dbu
2
Scheme 36: Synthesis of Ru(C≡CC≡CFc)(dppe)Cp and Ru(C≡CC≡CFc)(dppm)Cp
The mixed-metal complex {Re(PPh3)(NO)Cp*}(C≡CC≡C){Fe(dppe)Cp*} was
synthesised from the reaction of Re(C≡CC≡CTMS)(PPh3)(NO)Cp* with
FeCl(dppe)Cp* in the presence of KF, K[PF6] and 18-crown-6 in MeOH/THF
(Scheme 37).9
C CRe
ON
KF/K[PF6]
FeCl(dppe)Cp*C C TMS
Ph3P18-crown-6
C CRe
ON
C CPh3P
Fe
PPh2Ph2P
Scheme 37: Synthesis of {Re(PPh3)(NO)Cp*}(C≡CC≡C){Fe(dppe)Cp*}
24
1.3. The syntheses of trinuclear complexes
Currently, complexes of the general formula {LnM}-(C≡C)m-{MLn} include carbon
chains containing from two up to 28 carbon atoms joining the two metal-ligand
centres.3,12,13 However, as the chain length increases the synthesis becomes more
difficult and the stability of the compounds slowly decreases, especially with electron-
rich termini. Hence, the focus has been shifted to the introduction of a central bridging
group within the carbon chain. The central bridging group can be either an organic or
organometallic moiety. This is a convenient way to modify the physical properties of
the corresponding complex.
1.3.1. Organic linkers
First, the insertion of an organic moiety into these unsaturated carbon chains was
proposed. The reaction of 1,4-diethynylbenzene with two equivalents of a metal-
ligand fragment afforded, under various conditions, complexes of general formula
1,4-[{LnM}(C≡C)]2C6H4. Several examples have been described in the literature and
are summarised in Scheme 38.53-58 It was found that the insertion of the 1,4-
diethynylbenzene linker improved the stability of the complexes.
C CH C C H C C{LnM} C C {MLn}
{MLn} = RuCl(dppm)2; OsCl(dppm)2; FeCl(depe)2 RuCl(dppe)2; Ru(dppe)Cp*; Ru(dppe)Cp Fe(dppe)Cp*; Ru(PPh3)2Cp; Fc
{MLn}X
Scheme 38: Synthesis of complexes of general formula 1,4-[{LnM}(C≡C)]2C6H4
One example also involved the synthesis of a complex containing two W(CO)3CpC4
groups linked by the 1,4-phenylene unit. The complex 1,4-
[{W(CO)3Cp}(C≡CC≡C)]2C6H4 was synthesised in very good yield from the reaction
between 1,4-diiodobenzene and two equivalents of W(C≡CC≡CH)(CO)3Cp in the
presence of palladium/copper catalyst (Scheme 39).59
25
C CCp(OC)3W C C H + I I
Pd(PPh3)4CuITHF/NHPri
2
C CCp(OC)3W C C CC W(CO)3CpCC
Scheme 39: The synthesis of 1,4-{W(CO)3Cp}(C≡CC≡C)]2C6H4
Other examples of organic linkers are 2,5-thiophenediyl and 9,10-anthracenediyl.
Complexes of general formula 2,5-[{LnM}-C≡C-C4H2S-C≡C-{MLn}] where {MLn}
is Fe(dppe)Cp*,60 RuCl(dppm)2,54 OsCl(dppm)254 and Fc58 have been reported
(Figure 4).
C C{LnM} C C {MLn}
{MLn} = RuCl(dppm)2; OsCl(dppm)2; Fe(dppe)Cp*; Fc
S
Figure 4: Examples of 2,5-[{LnM}-C≡C-C4H2S-C≡C-{MLn}] complexes
A few complexes containing the 9,10-anthracenediyl moiety have also been
synthesised, such as {Cp*(dppe)M}-C≡C-C14H8-C≡C-{M(dppe)Cp*} (where M = Ru
and Fe) and the mixed-metal complex {Cp*(dppe)Fe}-C≡C-C14H8-C≡C-
{Ru(dppe)Cp*}(Figure 5).58,61
C C {MLn}C C{LnM}
{MLn} = Fe(dppe)Cp*; Ru(dppe)Cp*
Figure 5: {Cp*(dppe)M}-C≡C-C14H8-C≡C-{M(dppe)Cp*} (where M = Ru and Fe)
26
1.3.2. Organometallic linkers
Secondly, organometallic linkers can be used as the central bridging unit between two
metal-ligand centers. For example, the two redox-active ferrocene or ruthenocenyl
moieties have been employed as the central bridging group for several complexes of
general formula {LnM}-C≡C-Mc-C≡C-{MLn} (where Mc = 1,1’-M(η-C5H4)2, {MLn}
= Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp) (Figure 6).62,63
C C {MLn}
C C{LnM}
M = Fe, Ru{MLn} = Ru(dppe)Cp*; Ru(dppe)Cp; Ru(PPh3)2Cp
M
Figure 6: {LnM}-C≡C-Mc-C≡C-{MLn} complexes Similarly, the Ru(dppe)2 and Ru(dppm)2 metal-ligand fragments have also been used
as potential bridging groups as shown in Figure 7.58
Fe
C C Ru C C
Fe
PPh2Ph2P
Ph2P PPh2
n
n
n = 1, 2
Figure 7: Example of complexes with a Ru metal-ligand bridging group Furthermore, the synthesis of bis(diyndiyl) complexes of the general formula {LnM}-
C≡CC≡C-M”-C≡CC≡C-{M’Lm} has been developed. These complexes have two
transition metal fragments {LnM}-C≡CC≡C linked by a third metal centre. They have
been synthesised by various methods.
27
For example, two different mercury trimetallic complexes have been synthesised from
the reactions of Ru(C≡CC≡CH)(PR3)2Cp’ [(PR3)2 = dppe, Cp’ = Cp*; PR3 = PPh3,
Cp’ = Cp] and Hg(OAc)2 in THF (Scheme 40).64
RuR
RR
R
R C C C C Hg C C C C Ru R
R
RR
R(PR3)2
(PR3)2
(PR3)2 = dppe, R = Me or PR3 = PPh3, R = H
RuR
RR
R
R C C C C
(PR3)2
Hg(OAc)2THF
∆
H
Scheme 40: Synthesis of Hg{C≡CC≡C[Ru(PR3)2Cp’]}2 complexes
Similarly, the reactions of the diynyl complexes W(C≡CC≡CH)(CO)3Cp and
Au(C≡CC≡CH)(PR3) (where R = Ph, tol) with Hg(OAc)2 also afforded the trimetallic
complexes Hg[C≡CC≡C{MLn}]2 (where {MLn} = W(CO)3Cp, Au(PR3)).31,59
In addition, the reaction of trans-PdCl2(PEt3)2 with Re(C≡CC≡CLi)(PPh3)(NO)Cp*
(obtained from the treatment of Re(C≡CC≡CH)(PPh3)(NO)Cp* and n-BuLi) gives the
palladium complex trans-[{Re(PPh3)(NO)Cp*C4}2Pd(PEt3)2] in 73% yield (Scheme
41).22
28
C Pd C C
ON
PPh3
NO
PEt3
PEt3
Re C C C C C Re
Ph3P
C C C C HReON
(PPh3)
n-BuLi
-80oCTHF
C C C C LiReON
(PPh3)
PdCl2(PEt3)2-80oCTHF
Scheme 41: Synthesis of trans-[{Re(PPh3)(NO)Cp*C4}2Pd(PEt3)2]
Another method for the synthesis of bis(diyndiyl) complexes involves the CuI-
catalysed coupling of bis(diynyl) complex with a metal halide in amine solvents. For
example, the complexes trans-Pt{(C≡CC≡C)[M(PBu3)2Cl]}2(PBu3)2 (M = Pd, Pt)
were synthesised from the reactions of Pt(C≡CC≡CH)2(PBu3)2 with two equivalents
of trans-MCl2(PBu3)2 in the presence of CuI and NHEt2 (Scheme 42).16 Similarly, the
coupling of W(C≡CC≡CH)(CO)3Cp with cis-PtCl2(L2) species gave the complexes
cis-Pt{(C≡CC≡C)[W(CO)3Cp]}2(L2) (where L2 = dppe, dppp; L = PEt3).31
C C C C HPt
PBu3
PBu3
C C C CH
trans-MCl2(PBu3)2CuI/NHEt2
M = Pd (65%), Pt (40%)
C C C C MPt
PBu3
PBu3
C C C CM
PBu3
PBu3
Cl
PBu3
PBu3
Cl
Scheme 42: Synthesis of trans-Pt{(C≡CC≡C)[M(PBu3)2Cl]}2(PBu3)2 (M = Pd, Pt)
29
The reaction of [ppn][Au(acac)2] with diynyl complexes {MLn}(C≡CC≡CH) (where
{MLn} = W(CO)3Cp, Au(PPh3)) in a NHEt2/CH2Cl2 solvent gave the trimetallic
complexes in good yield as shown in Scheme 43.65
C CC C{LnM} H
NHEt2/CH2Cl2
C CC C {MLn}AuCC CC{LnM}
{MLn} = W(CO)3Cp (85%) = Au(PPh3) (73%)
[ppn][Au(acac)2]
ppn
+
Scheme 43: Synthesis of [ppn][Au{C≡CC≡C{MLn}}2]
Finally, the bis(ferrocenylalkynyl)ruthenium complex trans-Ru(C≡CC≡CFc)2(dppe)2
was synthesised by a different method.66 It was obtained from the reaction of
RuCl2(dppe)2 and the terminal alkyne FcC≡CC≡CH in the presence of Na[PF6] and
NEt3 (Scheme 44). This complex possesses a Ru(dppe)2 moiety as the central linking
group between the two carbon chains.
C C C C H
CCC C Ru
Ph2P PPh2
PPh2Ph2P
C C CC
CH2Cl2
Ru
Ph2P PPh2
PPh2Ph2P
Cl
Na[PF6] NEt3
+
Fe
Fe Fe
Cl
Scheme 44: Synthesis of trans-[Ru(C≡CC≡CFc)2(dppe)2] complex
30
1.4. Molecular wires
The miniaturisation of various electronic devices and their components has fascinated
and inspired the scientific community for many years. In 1949, the first digital
computer weighed as much as six elephants and filled a room big enough to hold
twenty of them.67 Less than sixty years later, we are able to make much smaller and
more powerful computers. This revolution in electronics came with the invention of
the integrated circuit which is described as a series of electronic devices layered in a
precise configuration in silicon, a semi-conducting material.68 Continual progress in
this field is driven by the fabrication of ever-smaller devices within the integrated
circuit. However, some limitations to this technology have raised concern and
researchers are now attempting to build new materials using the simplest molecular
building blocks, atoms and molecules. Recently, the field of molecular circuits has
expanded with the synthesis of molecular wires,69-72 switches,73-75 memories76,77 and
diodes.78
Any molecular circuit is composed of molecular wires which allow the current to flow
from one end of the molecule to the other. A molecular wire is defined as a “one
dimensional molecule allowing a through-bridge exchange of an electron/hole
between its remote ends/terminal groups, themselves able to exchange electrons with
the outside world”.69 The three most promising candidates for molecular wires are
conjugated organic molecules,79,80 carbon nanotubes81 and redox-active complexes.82
A wide variety of organic molecular wires with impressive size (up to 128 Å) were
successfully prepared by linking various unsaturated organic units.79,83-87 One
example of such a molecule is shown in Figure 8. The alternating single and multiple
carbon-carbon bonds within these compounds provide a rigid backbone which
facilitates electron transport through their conjugated π-systems.
Et2N3
R R
8
128 Å
TMS
Figure 8: A potential organic molecular wire, R = 3-ethylheptyl
31
Furthermore, the application of carbon nanotubes in molecular electronics has become
very promising.70,88-90 They appear as a sheet of graphite with a hexagonal lattice
rolled into a seamless cylinder. The structural properties of the carbon nanotubes can
be changed, such as the number of layers, the diameter of the cylinder and the
wrapping angle. For example, three different wrapping angles are shown in Figure 9.
Structure (a) is the nanotube in the armchair configuration, while (b) and (c) are the
zigzag and the chiral forms, respectively.91 The conductivity of a carbon nanotube is
dependent on these structural differences.
Figure 9: Structural differences of carbon nanotubes91
Recently, organometallic chemists incorporated metal centres in molecular wires.69
Such organometallic molecular wires attracted interest due to the possibility of “fine-
tuning” the electronic properties of the wire, by varying the ligands on the metal
centres or by changing the oxidation state of the metals. Bimetallic compounds in
which unsaturated elemental carbon chains span two transition metals constitute the
most fundamental class of carbon-based molecular wires. They are described by the
general formula {LxM}-Cn-{M’L’x’} where MLx represents a metal-ligand fragment
and Cn is the conjugated bridging ligand.92 Most of the carbon chains contain yndiyl
32
-C≡C- or poly-yndiyl -{C≡C}n- units which have remarkable versatility and π-density
which allows the delocalisation of electrons. Furthermore, a redox-active molecular
wire works when an unpaired electron is transferred across the entire molecule. This
free electron is obtained by either the loss of an electron from the highest occupied
molecular orbital (HOMO) or the addition of an electron to the lowest unoccupied
molecular orbital (LUMO) of the neutral complex. The two metal termini are left in
different oxidation states, forming a mixed-valence complex. The free electron can
then reside on either metal terminus (Figure 10).
e-
e-
M MConjugated bridge
Figure 10: Schematic representation of electron transfer in a redox-active molecular wire
The Robin-Day classification of mixed-valence compounds can describe the degree of
electronic interactions between both capping redox-active metals of a molecular
wire.93 Consider the bimetallic complex {LxM}-Cn-{MLx} which possesses two
identical redox-active sites linked by a Cn spacer. There are three possibilities under
the Robin-Day classification:
(i) Class I complexes do not allow any communication between the metal
centres as a result of the bridging ligand Cn acting as an insulator. The
charge is totally localised on one of the redox centres.
(ii) Class II materials are complexes with weakly interacting redox centres.
The charge is not localised on one of the metal centres nor is it delocalised
over the whole molecule. This characteristic distinguishes these materials
from Class I and at least one spectroscopic method is able to differentiate
between the two metal termini.
33
(iii) Class III complexes allow communication between the metal termini.
There are very strong interactions between the two metal centres and the
bridging ligand Cn acts as a conductor. Therefore, the charge in this type of
compound is fully delocalised over the whole molecule. Oxidation of
these complexes occurs in a stepwise manner, one electron at a time.
Recently, a fourth class, between Class II and III, has been proposed.94 Complexes in
this class have an inter-valence charge transfer that is not solvent dependent. This
characterises them as class III complexes. However, it is possible to determine some
charge localisation through the use of IR and low temperature X-ray crystallography,
which indicates class II complexes. One such example is the Creutz-Taube ion
[{H3N)5Ru}2(µ-pz)]5+.94
1.4.1. Evaluation of molecular wires by cyclic voltammetry
Many compounds can be suggested as models for molecular wires, hence a given
compound should prove its ability to transfer electrons in order to be considered as a
molecular wire. Cyclic voltammetry is one of the most frequently used
electrochemical methods to evaluate the electronic interaction between two redox-
active centres because of its relative simplicity.95,96
Cyclic voltammetry is a method to evaluate the oxidation potential of molecules and
measure the current response between redox-active metal termini. This technique
employs a three-electrode system. The most important electrode is the working
electrode where the redox reaction of the analyte takes place. The second electrode is
the auxiliary electrode (also known as the counter electrode). Its purpose is to conduct
electricity from the signal source into the solution, maintaining the correct current.
The third electrode is the reference electrode with a known and constant potential
(Figure 11). The basic theory behind cyclic voltammetry is to trace the transfer of
electrons during an oxidation-reduction reaction. At the negative electrode, the anode,
electrons are given off, and oxidation takes place. At the positive electrode, the
cathode, the electrons are collected, and reduction occurs. This giving-and-taking of
electrons creates an electric current and a potentiometer measures the current response
against the voltage.97
34
Figure 11: Cyclic voltammetry experimental set-up: the cell
The cyclic voltammetry experiment involves applying a triangular voltage as shown
in Figure 12. The experiment starts off with an initial potential Einitial at which no
redox reaction can take place. A forward scan is then performed by increasing the
potential linearly until it reaches the switching potential Eswitch and the cathodic
reaction is recorded. At this point, a reverse scan is carried out by decreasing the
potential back to the final potential Efinal measuring the anodic reaction.
Figure 12: Applied waveform used in a cyclic voltammetry experiment
A theoretical trace of a fully reversible one-electron process is shown in Figure 13.
From this trace, it is possible to measure both the cathodic ic and anodic ia peak
currents and the half-wave potential E1/2 which is the average between the anodic
potential Ea and the cathodic potential Ec (Equation 1).98
35
( )Ca EEE += 21
2/1 Equation 1
Figure 13: Theoretical trace of a fully reversible redox event
Furthermore, to obtain accurate voltammograms, measurements must be taken under
the conditions of a stationary working electrode and an unstirred solution. The way in
which redox-active complexes move between the bulk solution and the interface
double layer, called the mass transport, must be controlled by diffusion (Figure 14).98
+
+++
+++++
-----------
Double layer
Electrode
Diffusionlayer
Bulk
SolutionInterface
Figure 14: Enlarged view of the area around the working electrode
36
If the mass transport is controlled by diffusion, the current intensity (peak height of
the relevant redox event) is related to the square-root of the scan rate (Equation 2).98
i α ν Equation 2
A plot of the peak current versus the square root of the scan rate will show a linear
relationship for a fully reversible system. The ratio between the cathodic and anodic
currents will be equal to 1 for a fully reversible process, i.e., ic/ia = 1. In the case of a
partially reversible process, 1 > ic/ia > 0 while for a fully non-reversible event, ic/ia = 0
and is independent of scan rate.
For a symmetric molecular wire of general formula {LxM}-Cn-{MLx}, the difference
between successive oxidation potentials in the cyclic voltammogram is identified as
∆Eo. The value of ∆Eo is determined by the extent of the interactions between the two
termini of the wire: the greater the value, the greater the electronic communication
between the metal termini and the more efficient the complex is as a molecular
wire.69,99,100 Two cases were determined. The first one shows no interaction between
the two redox centres since the spacer acts as an insulator (Class I). Both metal
centres will be oxidised and reduced at the same potential and the cyclic
voltammogram will show a single wave representing a two-electron redox process
(Figure 15a).101 The oxidation potential of the two metal centres will only differ by a
small statistical factor described by ∆Eo = 2(RT/F)ln2, where R is the molar gas
constant, T is the temperature and F is the Faraday constant. The second case involves
a molecule with strong interactions between the two metal centres (Class III). The
cyclic voltammogram will show a minimum of two well-separated waves, each
corresponding to a one-electron process (Figure 15b).10 The formation of the mono-
oxidised species generates the first oxidation wave, while the second wave
corresponds to the formation of the doubly oxidised species. For Class III complexes,
electronic communication is high as ∆Eo is usually greater than 0.2 V. A molecular
wire is therefore a Class III material.69 For a class II complex, the relationship
between ∆Eo and the electron delocalisation becomes complicated as structural
reorganisation, solvation or ion pairing can affect ∆Eo values.
37
Figure 15: Cyclic voltammogram of class I (a) and class III (b) binuclear complexes
The diyndiyl complex {Cp(PPh3)2Ru}(C≡CC≡C){Ru(PPh3)2Cp} is a typical example
of a class III molecule.7 Its cyclic voltammogram shows four waves, each
representing a one-electron redox process, with three waves being fully reversible and
the last being irreversible. The large values of ∆Eo imply that strong interactions occur
between the metal termini and the carbon chain acts as a conductor. The presence of
four oxidation waves suggests that the stepwise oxidation of the neutral molecule to
the +4 state occurs via four one-electron redox events which may be represented by
the structural changes in the carbon bridge shown in Figure 16.7
38
[Ru] C C C C [Ru]
[Ru] C C C C [Ru]
[Ru] C C C C [Ru]
[Ru] C C C C [Ru]
[Ru] C C C C [Ru]
-e-
-e-
-e-
-e-
1+
2+
3+
4+
[Ru] = Ru(PPh3)2Cp
Figure 16: Stepwise oxidation of {Cp(PPh3)2Ru}(C≡CC≡C){Ru(PPh3)2Cp}
39
The molecular orbital (MO) diagram of the model complex {Cp(PH3)2Ru}(C≡C-
C≡C){Ru(PH3)2Cp} was prepared using theoretical calculations (Figure 17). This
diagram offers a better understanding of the bonding occurring between the C4 chain
and the two metal centres. This MO diagram shows that the bonding between the
metal and the carbon chain is of σ- and π-bonding nature.
The σ-type interactions are located between the high-lying metallic frontier molecular
orbitals (FMOs) 3bu and 3ag and the low-lying C4 orbitals 1bu and 2ag. These
interactions contribute to donation of electron density from the carbon chain towards
the metal. The σ-type bonding is complemented by relatively weak π-type back-
bonding from occupied metallic FMOs into the high-lying acceptor C4 FMOs 1au and
2bu. The large energy difference between these orbitals limits the degree to which
these back-bonding interactions may contribute to the metallic and organic fragments
bonding.
The predominant π-type interactions are filled/filled interactions between the FMOs
of the C4 spacer (1bg and 1ag) and the corresponding occupied metallic FMOs with the
same symmetry (1bg and 2ag). These interactions stabilise the C4 orbitals while the
metallic orbitals are destabilised and become the HOMOs of the neutral system. As a
consequence of these π interactions, a large percentage contribution takes place from
the carbons atoms of the C4 chain to the HOMOs of the neutral molecule. Therefore,
the HOMOs are delocalised over the entire six-atom Ru-C4-Ru chain and any
oxidation process which involves loss of electrons from these orbitals will not be
exclusively metal-centered.
In addition, it can be seen in the middle of Figure 17 that the HOMOs are well
separated from the high-lying LUMOs 2au and 3bu (3.37 eV) and the other lower-
lying occupied MOs. Therefore, it is expected that {Cp(PH3)2Ru}(C≡C-
C≡C){Ru(PH3)2Cp} will be able to lose up to four electrons, two from each HOMO,
giving rise to a total of five potential oxidation states. We can assume that similar
results will be obtained for the complex {Cp(PPh3)2Ru}(C≡CC≡C){Ru(PPh3)2Cp} as
the only difference is due to the substitution of PPh3 for PH3 to simplify the
calculations. This was confirmed experimentally by the cyclic voltammogram.7
40
Figure 17: Molecular orbital diagram of {Cp(PH3)2Ru}(C≡CC≡C){Ru(PH3)2Cp}
41
1.5. Work described in this thesis
In this thesis, the effect of inserting a central bridging group within the carbon chain is
investigated with the inclusion of the Ru(dppe)2 and the copper(I) or silver(I) cluster
M3(µ-dppm)3 (M = Cu, Ag) bridging ligands. Several symmetric and asymmetric
bis(diyndiyl) ruthenium(II) complexes of the general formula {LnM}-C≡CC≡C-
{M”L”p}-C≡CC≡C-{M’L’m} were synthesised. The electrochemistry of each of these
complexes is examined to determine if the insertion of the bridge allows or inhibits
the electronic communication between the two terminal redox-active groups. The
electronic interactions are also compared to those of complexes with longer straight
carbon chains.
Furthermore, the development of a synthetic route for the synthesis of diynyl and
diyndiyl ruthenium(II) complexes is described. The lithiation of the ruthenium(II)
diynyl complexes Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp gives
lithio derivatives of assumed formula [Ru](C≡CC≡CLi) (where [Ru] = Ru(dppe)Cp*,
Ru(PPh3)2Cp). These then react further with metal halides, organic and
polyfluoroaromatic reagents to give new diynyl and asymmetric diyndiyl complexes.
This new synthetic route allows the synthesis of several complexes which could not
be obtained from previously known methods. The complexes synthesised were
characterised by spectroscopic methods and where possible X-ray structure
determination. The electrochemistry of some of these complexes is also described.
In addition, the reactions of various diynyl and acetylene ruthenium(II) complexes
with azide reagents are explored. These reactions are expected to be related to “Click
Chemistry”, in particular the Huisgen 1,3-dipolar cycloaddition of the alkynes with
the azides to generate 1,2,3-triazoles. However, the reactions did not proceed as
expected, but gave a range of novel products which are characterised using both
spectroscopic and structural methods.
Chapter 2
The Chemistry of Bis(Diyndiyl) Ruthenium(II) Complexes
43
2.1. Introduction
Metal complexes with a conjugated carbon bridge have currently attracted great
attention because of their potential applications in molecular electronics. Many
diyndiyl compounds {LnM}-C≡CC≡C-{MLn} (where MLn is a metal-ligand fragment)
containing various redox-active metal centers have been prepared with metal termini
including Fe(dppe)Cp*,46 Re(PPh3)(NO)Cp*,44 Ru(PPh3)2Cp7 and Ru(dppe)Cp*102 for
example. These complexes show strong electronic interactions between the two redox-
active metal termini through the conjugated C4 chain (Figure 18a).
An exciting development has been the synthesis of bis(diyndiyl) complexes of the
general formula {LnM}-C≡CC≡C-{M”L”p}-C≡CC≡C-{M’L’m}. These complexes
have two transition metal fragments linked by a third metal centre. It is interesting to
evaluate the electronic properties associated with these types of complexes and to
determine if there is any electronic communication through the central organometallic
moiety or not (Figure 18b).
M Carbon Chain M
e-
(a)
M Carbon Chain M
e-
Carbon Chain M
(b) Figure 18: Electron delocalisation on various molecular wires
Few bis(diyndiyl) complexes have been synthesised until now and their central
bridging group can be classified in two categories. This group can either act as an
insulator by inhibiting the electronic communication through the carbon chain or it
can act as a conductor allowing electronic communication between the two terminal
metals.
One such example of a bis(diyndiyl) complex was synthesised from the reaction
between Ru(C≡CC≡CH)(dppe)Cp* and Hg(OAc)2 in THF to afford the complex
Hg{C≡CC≡C[Ru(dppe)Cp*]}2 (Figure 19).64
44
C C C CRuPh2P
PPh2
Hg C C C C Ru
Ph2P PPh2
Figure 19: The complex Hg{C≡CC≡C[Ru(dppe)Cp*]}2
The electronic structure of this compound was analysed using Extended Hückel (EH)
and Density Functional Theory (DFT) molecular orbital calculations, carried out on
the hydrogen-substituted model complex Hg{C≡CC≡C[Ru(dHpe)Cp*]}2 [dHpe =
H2P-(CH2)2-PH2]. The DFT molecular orbital plot of the HOMO is shown in Figure
20. The theory shows that there is a lack of Hg contribution in the HOMO which
prevents any electronic communication between the ruthenium termini and this was
confirmed by cyclic voltammetry. Hence, it can be concluded that the mercury atom
in Hg{C≡CC≡C[Ru(dppe)Cp*]}2 acts as an insulator.64
Figure 20: DFT molecular orbital plot of the HOMO of Hg{C≡CC≡C[Ru(dHpe)Cp*]}2
The same situation was found to occur when Pt, Pd and Cu metals were incorporated
into the bridging carbon chains.103 For example, the electrochemistry of the palladium
complex trans-[{Re(NO)(PPh3)Cp*C4}2Pd(PEt3)2] (Figure 21) was investigated. In
this instance, the ESR spectra of the monocation showed that the unpaired electron is
localised on the rhenium atom. Hence, the -C≡CC≡C-Pd-C≡CC≡C- linkage does not
45
allow electron delocalisation between the rhenium termini, and it is believed that the
palladium atom provides the principal barrier to delocalisation. This is another
example of a bis(diyndiyl) complex with no communication between the metal
centres.22
C Pd C C
ON
PPh3
NO
PEt3
PEt3
Re C C C C C Re
Ph3P
Figure 21: Molecular structure of trans-[{Re(NO)(PPh3)Cp*C4}2Pd(PEt3)2]
By contrast, bis(alkynyl)ruthenium systems were reported to allow communication
between the two end-groups. For example, the middle ruthenium moiety of the
complexes [cis-Ru(C≡CFc)2(dppm)2]CuI and trans-Ru(C≡CFc)2(PBu3)2(CO)(L) (L =
CO, pyridine or P(OMe)3) allows electronic interactions between the terminal
ferrocenyl groups (Figure 22 and Figure 23).104
Ru
PPh2
PPh2
Ph2P
Ph2P
Fe
Fe
Cu I
Figure 22: [cis-Ru(C≡CFc)2(dppm)2]CuI
Fe
C C Ru C C
Fe
L PBu3
Bu3P CO
L = CO, C5H5N, P(OMe)3
Figure 23: Ru(C≡CFc)2(PBu3)2(CO)(L)
46
Furthermore, in 1998 Dixneuf and co-workers reported the synthesis of a
bis(ferrocenylalkynyl)ruthenium complex trans-[Ru(C≡CC≡CFc)2(dppe)2] which
shows electronic communication from one end of the organometallic complex to the
other.66 This complex possesses a Ru(dppe)2 moiety as the central linking group of the
two carbon chains (Figure 24). It was synthesised from the reaction of RuCl2(dppe)2
and FcC≡CC≡CH in the presence of Na[PF6] and NEt3.
In order to evaluate how the carbon-rich bridges and the Ru(dppe)2 moiety
communicate information from one end of the molecule to the other, the redox
potentials of the ferrocenyl and ruthenium moieties were measured using cyclic
voltammetry. The cyclic voltammogram of trans-[Ru(C≡CC≡CFc)2(dppe)2] is
composed of three redox potentials: two at -0.12 V and +0.01 V corresponding to the
oxidation of the ferrocenyl groups and one at +0.40 V for the RuII/RuIII system.66 Both
ferrocenyl and Ru(dppe)2 groups are reversibly oxidised and the ruthenium(II) moiety
behaves as a strong electron-donating centre. Thus, this study confirmed that the
Ru(dppe)2 moiety allows electronic communication and that the -C≡C-C≡C- bridge is
very efficient in allowing electronic communication from one end of the linear
organometallic molecule to the ferrocenyl group at the other end. This complex shows
the potential of this particular ruthenium fragment as a connector between carbon-rich
systems to mediate electron conduction.
CCC C Ru
Ph2P PPh2
PPh2Ph2P
C C CC
Fe Fe
Figure 24: trans-[Ru(C≡CC≡CFc)2(dppe)2]
47
2.2. Aim of this work
The primary aim of this work is to develop a method for the synthesis of
bis(diyndiyl) ruthenium complexes of the general formula {LnM}-C≡CC≡C-
Ru(dppe)2-C≡CC≡C-{M’L’m}, featuring two transition metal fragments linked by a
trans-(C≡CC≡C)2Ru(dppe)2 moiety. Two different approaches to these complexes can
be taken with a double addition of the transition metal termini giving symmetric
complexes (where LnM = M’L’m) or sequential addition giving rise to the possibility
of asymmetric complexes (where LnM ≠ M’L’m).
An attractive feature of these bis(diyndiyl) ruthenium(II) complexes is the presence of
the Ru(dppe)2 moiety as the central bridging group. It was previously shown that the
Ru(dppe)2 moiety allows electron communication along a carbon chain. Hence, our
objective is to investigate further the electrochemical behavior of the new
bis(diyndiyl) complexes by using cyclic voltammetry and to demonstrate that the
Ru(dppe)2 moiety acts as a conductor in this type of complex.
Secondly, the trinuclear copper(I) or silver(I) clusters M3(µ-dppm)3 (M = Cu, Ag) are
proposed as different central bridging groups to link two ruthenium diynyl fragments.
Complexes of the general formula {Cp*(dppe)Ru}-C≡CC≡C-{M3(µ-dppm)3}-
C≡CC≡C-{Ru(dppe)Cp*} were synthesised and characterised. Cyclic voltammetry
can then be used to determine what effect the inclusion of the copper(I) and silver(I)
cluster has on the electronic communication between the two metal end-groups.
48
2.3. Results and Discussion
2.3.1. Symmetric complexes trans-Ru{C4[Ru]}2(dppe)2
The synthesis of symmetric bis(diyndiyl) complexes trans-Ru{C4[Ru]}2(dppe)2
(where [Ru] = Ru(dppe)Cp*, Ru(dppe)Cp or Ru(PPh3)2Cp) was achieved by the
reaction of trans-Ru(C4H)2(dppe)2 (1) with two equivalents of a chlororuthenium
complex in the presence of an excess of NEt3 and Na[BPh4]. The reaction mixture
was heated in a refluxing mixture of CH2Cl2/MeOH for two hours (Scheme 45). The
presence of the non-coordinating salt Na[BPh4] facilitates the ionisation of the Ru-Cl
bond while treatment with NEt3 leads to deprotonation of the vinylidene intermediate
to give the desired complex.
Ru
Ph2P PPh2
PPh2Ph2P
HC C C CC C C CH
2 eq [Ru]Cl 1:1 CH2Cl2/MeOHNa[BPh4]
Ru
Ph2P PPh2
PPh2Ph2P
[Ru]C C C CC C C C[Ru]
NEt3∆
(1)
[Ru] = Ru(dppe)Cp* (2), Ru(dppe)Cp (3) or Ru(PPh3)2Cp (4)
Scheme 45: Synthetic strategy for symmetric bis(diyndiyl) complexes
49
The symmetric bis(diyndiyl) complex trans-Ru{C4[Ru(dppe)Cp*]}2(dppe)2 (2) was
successfully synthesised as a yellow-green powder in 70% yield while the complexes
trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2 (3) and trans-Ru{C4[RuCp(PPh3)2]}2(dppe)2 (4)
were obtained as brown solids in 75% and 77% yields, respectively.
Complexes 2, 3 and 4 each contain three redox-active metal centres bridged by
butadiyndiyl chains. The Ru-C4-Ru-C4-Ru fragment forms an eleven-atom chain. The
central ruthenium has two dppe ligands attached, whereas the terminal rutheniums are
bound to various ligands. These complexes are therefore examples of trinuclear
complexes.
Complexes 2, 3 and 4 were fully characterised by 1H, 31P and 13C NMR, IR, ES-MS
and microanalysis. All the data are summarised in Table 1. The characteristic peaks
for the Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp ligands are present in the 1H, 31P
and 13C NMR spectra. In the 31P NMR spectrum of 2, 3 and 4, a singlet is also present
for the four equivalent phosphorus nuclei on the central ruthenium which indicates a
trans configuration. The carbons of the carbon chains were not observed in the 13C
NMR spectra due to the lack of solubility of the complexes in common NMR
solvents. However, the IR spectra of the three complexes contain ν(C≡C) bands
between 1969 and 2124 cm-1. Further characterisations of 2, 3 and 4 were obtained
from ES-MS which contained ions corresponding to [M]+, a fragment ion at m/z 898
for [Ru(dppe)2]+ and fragment ions for the corresponding Ru(dppe)Cp*, Ru(dppe)Cp
and Ru(PPh3)2Cp groups.
50
Table 1: Spectroscopic data for complexes 2 - 4
Complex IR (cm-1) ν(C≡C)
1H NMR (δ)
13C NMR (δ)
31P NMR (δ)
ES-MS (m/z)
2 2012 (m) 1969 (w)
7.72-7.04 (m, 80H, Ph); 2.60-2.55, 1.91-1.82 (2 x m, 16H, CH2CH2); 1.46 (s, 30H, Cp*)
135.46-129.61 (m, Ph); 97.80 (s, C5Me5); 31.49-31.15 (m, CH2CH2); 11.53 (s, C5Me5)
76.3 (s, Ru(dppe)Cp*) 53.4 (s, Ru(dppe)2)
2266, [M]+; 898, [Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+
3 2124 (m) 2013 (w)
7.67-7.16 (m, 80H, Ph); 4.35 (s, 10H, Cp); 2.23-2.19, 1.91-1.79 (2 x m, 16H, CH2CH2)
136.27-129.37 (m, Ph); 83.85 (s, C5H5); 29.09-28.34 (m, CH2CH2)
80.7 (s, Ru(dppe)Cp) 56.5 (s, Ru(dppe)2)
2123, [M]+; 2122, [M - H]+; 898, [Ru(dppe)2]+; 606, [Ru(NCMe)(dppe)Cp]+; 565, [Ru(dppe)Cp]+
4 2014 (w) 1979 (w)
7.71-6.93 (m, 100H, Ph); 4.36 (s, 10H, Cp); 2.31-2.19, 1.93-1.80 (2 x m, 8H, CH2CH2)
133.88-127.14 (m, Ph); 83.10 (s, C5H5); 30.09-29.56 (m, CH2CH2)
57.0 (s, Ru(dppe)2) 43.0 (s, Ru(PPh3)2)
2375, [M]+; 1685, [Ru(PPh3)2CpC4Ru(dppe)2C4]+
; 898, [Ru(dppe)2]+; 691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+
51
2.3.2. Asymmetric complexes trans-Ru{C4[Ru]}{C4H}(dppe)2
The strategy for the synthesis of asymmetric bis(diyndiyl) complexes involved the
reaction of trans-Ru(C4H)2(dppe)2 (1) with one equivalent of a chlororuthenium
complex in a CH2Cl2/MeOH solvent mixture. An excess of Na[BPh4] and NEt3 are
necessary for the ionisation of the Ru-Cl bond and the deprotonation step. The
reaction was complete after a 1 h reflux (Scheme 46).
Ru
Ph2P PPh2
PPh2Ph2P
HC C C CC C C CH
1 eq [Ru]ClCH2Cl2/MeOH
Na[BPh4]
Ru
Ph2P PPh2
PPh2Ph2P
HC C C CC C C C[Ru]
NEt3∆
[Ru] = Ru(dppe)Cp* (5), Ru(dppe)Cp (6) or Ru(PPh3)2Cp (7)
(1)
Scheme 46: Synthetic strategy for asymmetric bis(diyndiyl) complexes
The asymmetric bis(diyndiyl) complexes trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2
(5) and trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2 (6) were obtained as green solids in
80% and 85% yield, respectively. Trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) was
synthesised in 85% yield as a brown powder.
52
Complexes 5, 6 and 7 were readily identified from their spectroscopic data and
elemental analysis. Table 2 summarises the data obtained. In the 1H, 31P and 13C NMR
spectra, the characteristic peaks for the Ru(dppe)Cp*, Ru(dppe)Cp, Ru(PPh3)2Cp and
Ru(dppe)2 ligands are present. The 1H NMR spectra of 5, 6 and 7 also show a singlet
corresponding to the terminal hydrogen at δ 1.44, 1.41 and 1.40, respectively. The
infrared spectrum of the three complexes contain different bands assigned to ν(C≡C)
and ν(≡CH). The ES-MS of complexes 5, 6 and 7 contain strong [M]+ ions, with
fragmentation ions for Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp.
53
Table 2: Spectroscopic data for complexes 5 - 7
Complex IR (cm-1)
1H NMR (δ)
13C NMR (δ)
31P NMR (δ)
ES-MS (m/z)
5 ν(≡CH) 3055 (m); ν(C≡C) 2022 (w), 1968 (w)
7.99-7.12 (m, 60H, Ph); 2.47-2.44, 2.10-2.03 (2 x m, 12H, CH2CH2); 1.56 (s, 15H, Cp*); 1.44 (s, H)
136.32-127.32 (m, Ph); 96.91 (s, C5Me5); 31.51-30.22 (m, CH2CH2); 10.64 (s, C5Me5)
70.5 (s, Ru(dppe)Cp*) 46.1 (s, Ru(dppe)2)
1631, [M]+; 898, [Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+
6 ν(≡CH) 3053 (w); ν(C≡C) 1995 (m), 1919 (m)
7.42-6.87 (m, 60H, Ph); 4.50 (s, 5H, Cp); 2.55-2.51, 2.11-2.04 (2 x m, 12H, CH2CH2); 1.41 (s, H)
136.01-125.22 (m, Ph); 84.84 (s, C5H5); 30.54-29.27 (m, CH2CH2)
81.5 (s, Ru(dppe)Cp) 56.4 (s, Ru(dppe)2)
1560, [M]+; 898, [Ru(dppe)2]+; 605, [Ru(NCMe)(dppe)Cp]+; 563, [Ru(dppe)Cp]+
7 ν(≡CH) 3055 (w); ν(C≡C) 1981 (m), 1896 (m)
7.76-6.91 (m, 70H, Ph); 4.20 (s, 5H, Cp); 2.39-2.37, 2.10-2.06 (2 x m, 8H, CH2CH2); 1.40 (s, H)
133.97-125.72 (m, Ph); 81.48 (s, C5H5); 31.03-30.22 (m, CH2CH2)
53.0 (s, Ru(dppe)2) 40.0 (s, Ru(PPh3)2Cp)
1685, [M]+; 898, [Ru(dppe)2]+; 690, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+
54
2.3.3. Asymmetric complexes trans-Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2
Previously, diyndiyl complexes of general formula {LnM}-C≡CC≡C-{MLn} have
been synthesised.7 Studies have been concentrated on the synthesis of complexes
containing C4 chains capped at each end by two identical or different MLn groups and
various methods have been described in Chapter One. One synthetic route for the
synthesis of asymmetric complexes is based on the reaction of a diynyl with one
equivalent of a metal halide in presence of a non-coordinating salt and excess of a
base. The use of the salt is very important in this reaction as it assists with the
ionisation of the metal-chloride bond and the presence of excess base allowed the
intermediate to be deprotonated immediately upon formation, thereby preventing any
side reactions from occurring. One such example is the synthesis of mixed ruthenium-
iron diyndiyls shown in Scheme 47.12
C C C CRu
Ph2P PPh2
H + Cl Fe
Ph2P PPh2
(CH2)n
Na[BPh4]/dbu
NEt3
C C C CRu
Ph2P PPh2
Fe
Ph2P PPh2
(CH2)n
Scheme 47: Synthesis of {Cp*(dppe)Ru}(C≡CC≡C){Fe(PP)Cp*} (PP = dppe, dppp)
55
Consequently, the asymmetric complexes trans-Ru{C4[Ru]}{C4H}(dppe)2 (where
[Ru] = Ru(dppe)Cp* (5), Ru(dppe)Cp (6) or Ru(PPh3)2Cp (7)) synthesised in Section
2.3.2 offer a wide range of possibilities for new chemistry. The terminal hydrogen
atom can be readily replaced by different end-groups, giving a new route for the
synthesis of asymmetric trinuclear complexes.
Hence, the reaction of trans-Ru{C4[Ru]}{C4H}(dppe)2 (where [Ru] = Ru(dppe)Cp*
(5) or Ru(PPh3)2Cp (7)) with one equivalent of the chlororuthenium complex
RuCl(dppe)Cp in the presence of an excess of NEt3 and Na[BPh4] afforded the
asymmetric complexes trans-Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2 (8)
and trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2 (9) in 77% and 78%
yields, respectively (Scheme 48).
Ru
Ph2P PPh2
PPh2Ph2P
HC C C CC C C C[Ru]
1 eq RuCl(dppe)Cp 1:1 CH2Cl2/MeOH
Na[BPh4]
Ru
Ph2P PPh2
PPh2Ph2P
[Ru(dppe)Cp]C C C CC C C C[Ru]
NEt3 ∆
[Ru] = Ru(dppe)Cp* (5) or Ru(PPh3)2Cp (7)
[Ru] = Ru(dppe)Cp* (8) or Ru(PPh3)2Cp (9)
Scheme 48: Synthetic strategy for 8 and 9
56
Complexes 8 and 9 were fully characterised by 1H, 31P and 13C NMR, IR, ES-MS and
microanalysis. The data are summarised in Table 3. In the NMR spectra, the
characteristic peaks for the Ru(dppe)2, Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp
ligands were present for both complexes. The infrared spectra of complexes 8 and 9
show the loss of the ν(≡CH) band and the presence of ν(C≡C) bands. Furthermore,
the ES-MS of 8 and 9 show the fragment ions for the different terminal ligands.
57
Table 3: Spectroscopic data for complexes 8 and 9
Complex IR (cm-1) ν(C≡C)
1H NMR (δ)
13C NMR (δ)
31P NMR (δ)
ES-MS (m/z)
8 2021 (m), 1961 (m)
7.88-6.90 (m, 80H, Ph); 4.59 (s, 5H, Cp); 2.98-2.84, 2.24-2.16 (m, 16H, CH2CH2); 1.45 (s, 15H, Cp*)
134.82-127.03 (m, Ph); 99.92 (s, C5Me5); 81.76 (s, C5H5); 30.82-29.97 (m, CH2CH2); 9.89 (s, C5Me5)
80.7 (s, Ru(dppe)Cp) 76.4 (s, Ru(dppe)Cp*) 55.6 (s, Ru(dppe)2)
2194, [M + H]+; 1629, [M - Ru(dppe)Cp]+; 898, [Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+; 675, [Ru(NCMe)(dppe)Cp*]+; 565, [Ru(dppe)Cp]+; 605, [Ru(NCMe)(dppe)Cp]+
9 2017 (m),
1888 (w) 7.87-6.93 (m, 75H, Ph); 2.71-2.57, 2.42-2.37 (2 x m, 12H, CH2CH2); 4.58 (s, 5H, Cp); 4.32 (s, 5H, Cp)
135.47-128.56 (m, Ph); 81.25 (s, C5H5); 80.93 (s, C5H5); 30.10-29.20 (m, CH2CH2)
80.7 (s, Ru(dppe)Cp) 55.9 (s, Ru(dppe)2) 42.9 (s, Ru(PPh3)2)
1685, [Ru(PPh3)2CpC4Ru(dppe)2C4]+ ; 1559, [Ru(dppe)CpC4Ru(dppe)2C4]+; 898, [Ru(dppe)2]+; 690, [Ru(PPh3)2Cp]+; 605, [Ru(NCMe)(dppe)Cp]+; 565 [Ru(dppe)Cp]+; 429, [Ru(PPh3)Cp]+
58
2.3.4. Synthesis of trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2
Previously, it was reported that the reaction of cis-RuCl2(dppe)2 with silver triflate
leads to the abstraction of one of the halide ligands to produce the complex cis-
[RuCl(dppe)2]OTf.105 This complex was shown to react with bis(propargylic) alcohols
to form allenylidene ruthenium complexes (Scheme 49).106
OTf
Ru Cl
Ph2P
Ph2P
PPh2
PPh2
Ru
Ph2P
Ph2P
PPh2
PPh2
Cl
Cl
AgOTf
H C C C C C C C C HOH
Ph
OH
Ph
Cl Ru
Ph2P
Ph2P
PPh2
PPh2
C C
Ph
CC
C
Ph
C C C Ru Cl
Ph2P
Ph2P PPh2
PPh2
2 OTf2+
Scheme 49: First example of reaction with cis-[RuCl(dppe)2]OTf Another example is the synthesis of the complex RuCl(C≡CCHPh2)(dppe)2 from
trans-[RuCl(dppe)2]OTf and H-C≡C-CPh2(OH). This reaction is done in two steps.
The first one affords the compound [RuCl(=C=C=CPh2)(dppe)2]OTf which is then
reduced using LiAlH4 to give the desired complex (Scheme 50).107
59
OTf
Ru Cl
Ph2P
Ph2P
PPh2
PPh2
+ H C C C
OH
Ph
Ph
CH2Cl2Cl Ru
Ph2P
Ph2P
PPh2
PPh2
C CPh
CPh
OTf
LiAlH4THF
Cl Ru
Ph2P
Ph2P
PPh2
PPh2
C CPh
CPh
H
Scheme 50: Second example of reaction with trans-[RuCl(dppe)2]OTf These reactions offer possibilities to link a ruthenium fragment to a carbon chain.
Hence, Ru(C≡CC≡CH)(dppe)Cp* reacts with one equivalent of [RuCl(dppe)2]OTf in
a CH2Cl2/NEt3 solvent mixture at room temperature for two days to afford the
complex trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 (10) in 83% yield (Scheme 51).
Ru
Ph2P PPh2
PPh2Ph2P
Cl+C C C CRu
Ph2P PPh2
H
1:1 CH2Cl2/NEt3
C C C CRu
Ph2P PPh2
Ru
Ph2P PPh2
PPh2Ph2P
OTf
(10)
Cl
Scheme 51: Synthesis of 10
Complex 10 was readily identified by elemental analysis and IR, ES-MS and NMR
spectroscopy. The IR spectrum shows two ν(C≡C) bands at 2037 and 1988 cm-1. The 1H NMR spectrum contains a multiplet at δ 7.72-6.90 for the protons of the phenyl
60
groups, two multiplets at δ 3.57-3.54 and 3.49-3.46 for the CH2CH2 protons of the
central Ru(dppe)2 unit and two multiplets at δ 2.86-2.76 and 1.87-1.75 for the
Ru(dppe)Cp* moiety. The 31P NMR spectrum of 10 contains a peak at δ 82.8 for the
phosphorus of the Ru(dppe)Cp* ligand and two equivalent triplets at δ 60.1 (18 Hz)
and 50.6 (18 Hz) for the phosphorus on the central ruthenium. This can be explained
by the phosphorus atoms of the Ru(dppe)2 unit being in different chemical
environment if it is assumed that there is a restricted rotation around the ruthenium.
The 13C NMR spectrum contains resonances assigned to the phenyl groups (δ 133.23-
128.11), Cp* (δ 93.26, 9.82) and CH2 (δ 32.22-31.79). The ES-MS includes a peak for
[M - H]+ at m/z 1615, a peak at m/z 898 for [Ru(dppe)2]+ and a peak at m/z 635 for
[Ru(dppe)Cp*]+.
The successful synthesis of this complex suggests a new route for the potential
synthesis of bis(diyndiyl) complexes as the presence of the chloride atom offers a
possible site for connecting different end-groups. Substitution of the chloride atom on
10 for a Ru(C≡CC≡C)(dppe)Cp* fragment was attempted using various conditions,
but the formation of the expected complex was not observed, only decomposition
products being obtained.
2.3.5. Gold reactions
Gold(I) chemistry has interested researchers for many years. Several gold(I)
complexes have been used as precursors for alkynylgold(I) derivatives. These include
AuCl(L) (L = PPh3, SC4H8),108,109 (AuCl)2(µ-dppm)110 and [ppn][Au(acac)2].111 Some
gold(I) complexes of 1,3-butadiyne have been reported recently by our research
group.65 For example, the copper-catalysed coupling of AuCl(PPh3) and buta-1,3-
diyne under Cadiot-Chodkiewicz conditions results in the formation of
Au(C≡CC≡CH)(PPh3). This complex reacts further with AuCl(PPh3) under similar
conditions to afford {Au(PPh3)}2(µ-C≡CC≡C) (Scheme 52).65
61
+ H C CAuCl(PPh3)Cu(I)
THF/NHEt2(Ph3P)Au C C C CH
THF/NHEt2
(Ph3P)Au C C C C Au(PPh3)
AuCl(PPh3)Cu(I)
H2
Scheme 52: Synthesis of gold(I) complexes Furthermore, diynyl complexes have been shown to react with AuCl(PPh3) to give
heteronuclear diyndiyl complexes, such as the asymmetric diyndiyl
W{C≡CC≡C[Au(PPh3)]}(CO)3Cp synthesised from the reaction between
W(C≡CC≡CH)(CO)3Cp and AuCl(PPh3) (Scheme 53).65
Cp(OC)3W C C C CH
THF/NHEt2
Cu(I)
AuCl(PPh3)Cp(OC)3W C C C C Au(PPh3)
Scheme 53: Synthesis of W{C≡CC≡C[Au(PPh3)]}(CO)3Cp
Similarly, the reactions of Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp
with AuCl(PPh3) in the presence of K[N(TMS)2] afforded two new complexes
(Scheme 54).112
[Ru] C CC CHAuCl(PPh3)
[Ru] C C Au(PPh3)C C
[Ru] = Ru(dppe)Cp*, Ru(PPh3)2CpK[N(TMS)2]
Scheme 54: Synthesis of [Ru]{C≡CC≡C[Au(PPh3)]} In general, diyne complexes of general formula {MLn}(C≡CC≡CH) react with
AuCl(PPh3) to afford complexes of the type {MLn}(C≡CC≡C){Au(PPh3)}. Hence, the
reaction of the asymmetric complexes trans-Ru{C4[Ru]}{C4H}(dppe)2 (where [Ru] =
Ru(dppe)Cp* (5), Ru(dppe)Cp (6) or Ru(PPh3)2Cp (7)) with AuCl(PPh3) should show
a similar reaction pattern and result in the formation of complexes of the type trans-
Ru{C4[Ru]}{C4[Au(PPh3)]}(dppe)2.
62
2.3.5.1. Synthesis of trans-Ru{C4[Ru]}{C4[Au(PPh3)]}(dppe)2
The complexes trans-Ru{C4[Ru]}{C4H}(dppe)2 (where [Ru] = Ru(dppe)Cp* (5),
Ru(dppe)Cp (6) or Ru(PPh3)2Cp (7)) react with one equivalent of AuCl(PPh3) in the
presence of NaOMe in a mixture of 1:4 MeOH/THF to give trans-
Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11), trans-Ru{C4[Ru(dppe)Cp]}-
{C4[Au(PPh3)]}(dppe)2 (12) and trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2
(13) as pale yellow complexes in 70%, 62% and 69% yield, respectively (Scheme 55).
Ru
Ph2P PPh2
PPh2Ph2P
C C C CC C C C[Ru] Au(PPh3)
NaOMeAuCl(PPh3)
Ru
Ph2P PPh2
PPh2Ph2P
HC C C CC C C C[Ru]
1:4 MeOH/THF
[Ru] = Ru(dppe)Cp* (5), Ru(dppe)Cp (6) or Ru(PPh3)2Cp (7)
[Ru] = Ru(dppe)Cp* (11), Ru(dppe)Cp (12) or Ru(PPh3)2Cp (13)
Scheme 55: Reaction scheme for the synthesis of 11, 12 and 13
63
Complexes 11, 12 and 13 have very similar structures, the difference being the
presence of the different terminal ruthenium ligands. The three complexes were fully
characterised by NMR and infrared spectroscopy, and elemental analysis. All data are
described in Table 4. The NMR analyses confirmed the presence of the different
terminal groups (Ru(dppe)Cp*, Ru(dppe)Cp, Ru(PPh3)2Cp) and the Ru(dppe)2 moiety.
The 31P NMR spectra of complexes 11, 12 and 13 also show the expected peak for the
phosphorus of the Au(PPh3) unit and the Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp
groups. The carbon chains on the three complexes are characterised by ν(C≡C) bands
in the infrared spectra.
64
Table 4: Spectroscopic data for complexes 11 - 13
Complex IR (cm-1) ν(C≡C)
1H NMR (δ)
13C NMR (δ)
31P NMR (δ)
ES-MS (m/z)
11 2012 (w) 1957 (m)
7.69-7.04 (m, 75H, Ph); 3.52-3.15, 2.37-2.30 (2 x m, 12H, CH2CH2); 1.57 (s, 15H, Cp*)
139.31-121.36 (m, Ph); 98.80 (s, C5Me5); 30.63-29.65 (m, CH2CH2); 9.48 (s, C5Me5)
73.8 (s, Ru(dppe)Cp*) 55.3 (s, Ru(dppe)2) 44.6 (s, Au(PPh3))
2086, [M]+; 2055 [M - P]+; 1626, [M – Au(PPh3)]+
12 2013 (w) 1882 (w)
7.87-6.91 (m, 75H, Ph); 4.57 (s, 5H, Cp); 2.56-2.49, 2.33-2.24 (2 x m, 12H, CH2CH2)
142.68-122.00 (m, Ph); 84.97 (s, C5H5); 30.83-29.79 (m, CH2CH2)
80.7 (s, Ru(dppe)Cp) 53.3 (s, Ru(dppe)2) 44.6 (s, Au(PPh3))
2018, [M]+; 898, [Ru(dppe)2]+; 565 [Ru(dppe)Cp]+
13 1970 (w) 1899 (w)
7.79-6.86 (m, 85H, Ph); 4.36 (s, 5H, Cp); 2.30-2.25, 1.99-1.88 (2 x m, 8H, CH2CH2)
136.01-121.85 (m, Ph); 84.05 (s, C5H5); 31.12-29.25 (m, CH2CH2)
53.9 (s, Ru(dppe)2) 51.4 (s, Ru(PPh3)2Cp) 43.2 (s, Au(PPh3))
2113, [M - P]+; 2038, [M - PPh]+; 898, [Ru(dppe)2]+; 429, [Ru(PPh3)Cp]+
65
2.3.5.2. Synthesis of trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2
Recently, it was reported that reactions between aurated poly-ynes and halo-alkynes
result in a facile elimination of AuX(PR3) (X = halide, R = Ph, tol) and the formation
of new C-C bonds.30 The reactions are carried out in ether solvents (THF, Et2O) at
moderate temperatures in the presence of a Pd(0)/Cu(I) catalyst. This reaction may be
considered to be a variant of the well-known Sonogashira reaction.113-115 The
AuX(PR3) may be recovered and re-used. For example, this reaction was used to
make the complex Co3{µ3-C(C≡C)2TMS}(µ-dppm)(CO)7 by coupling
TMS(C≡C)2Au(PPh3) with Co3(µ3-CBr)(µ-dppm)(CO)7 (Scheme 56).30
CuI/Pd(PPh3)4THF
C C C C
(OC)2Co
Co(CO)3
C Co(CO)2
PPh2
Ph2P
(OC)2Co
Co(CO)3
C Co
PPh2
Ph2P
+ (CO)2
TMS
TMS C C Au(PPh3)2 Br
Scheme 56: Synthesis of Co3{µ3-C(C≡C)2TMS}(µ-dppm)(CO)7
The reaction of trans-Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11) with one
equivalent of Co3(µ3-CBr)(µ-dppm)(CO)7 in the presence of CuI and Pd(PPh3)4
afforded trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2 (14) (Scheme
57).
66
CuI/Pd(PPh3)4THF
Ru
Ph2P PPh2
PPh2Ph2P
C C C CC C C C
(OC)2Co
Co(CO)3
C Co(CO)2
PPh2
Ph2P
Ru
Ph2P PPh2
PPh2Ph2P
Au(PPh3)C C C CC C C C +Ru
Ph2P PPh2
Ru
Ph2P PPh2
(11)
(14)
(OC)2Co
Co(CO)3
C Co
PPh2
Ph2P
(CO)2Br
Scheme 57: Reaction scheme for the synthesis of 14
Complex 14 was obtained in 33% yield and characterised by 1H, 31P NMR, IR and
ES-MS. The infrared spectrum has two bands for the ν(C≡C) stretch at 2010 and 1978
cm-1, as well as bands for the ν(CO) stretch. The 1H NMR spectrum shows the
protons associated with the phenyl groups of the dppe and dppm ligands at δ 7.70-
6.83, the protons of the CH2CH2 unit of the dppe ligands as two multiplets at δ 2.85-
2.77 and 2.55-2.45 and these of the dppm ligand at δ 4.45-4.40 and 3.48-3.43. A
singlet at δ 1.51 corresponds to the Cp* ligand. The 31P NMR spectrum of 14 contains
three peaks, one at δ 72.8 for the phosphorus of the end-group ruthenium, one at δ
55.9 for the phosphorus on the middle ruthenium and at δ 30.6 for the phosphorus of
the dppm ligand. In the 13C NMR spectrum, the presence of a multiplet at δ 203.29-
200.02 indicates the CO groups. There are also two multiplets at δ 139.37-132.77 and
30.40-29.63 for the phenyl groups and the CH2CH2 unit of dppe respectively. The
dppm ligand is characterised by a multiplet at δ 33.95-32.22 corresponding to the CH2
group, and the Cp* ligand is confirmed by the presence of a singlet at δ 96.86 for the
C5Me5 atoms and at 10.11 for the methyl groups on the C5Me5 unit. The ES-MS of 14
contained a peak at m/z 2370 corresponding to [M - CO]+, a peak at m/z 898 for
[Ru(dppe)2]+ and a peak at m/z 675 for [Ru(dppe)Cp*]+.
67
Complex 14 is the first example of a complex containing both even- and odd-
numbered carbon chains connected by a Ru(dppe)2 unit. The formation of the new
carbon-carbon bond through the elimination of AuBr gives an odd-numbered C5 chain
connecting the cobalt cluster while the other C4 chain remains unchanged.
2.3.6. Various reactions of trans-Ru(C4H)2(dppe)2
2.3.6.1. Reaction with AuCl(PPh3)
According to previous studies described in Section 2.3.5, it was anticipated that
AuCl(PPh3) would react with the bis(diyndiyl) complex trans-Ru(C4H)2(dppe)2 (1) in
the presence of base. Hence, two equivalents of AuCl(PPh3) and 1 were coupled
together in a simple reaction using sodium methoxide (Scheme 58). This resulted in
the formation of a lemon-yellow complex, Ru{C4[Au(PPh3)]}2(dppe)2 (15), in 89%
yield.
Complex 15 was characterised by NMR, IR, ES-MS and elemental analysis. The
infrared spectrum shows two ν(C≡C) bands at 1974 and 2084 cm-1. The 1H NMR
spectrum of 15 shows a multiplet at δ 7.61-7.07 assigned to the aromatic hydrogens
and two multiplets at δ 3.76-3.59 and 2.61-2.51 which correspond to -CH2CH2-
groups of dppe. The 31P NMR spectrum shows a singlet at δ 53.1 arising from the
phosphorus nuclei coordinated to the ruthenium, and at δ 46.1 from the phosphorus
nucleus coordinated to the gold. In the 13C NMR spectrum, two multiplets were
present at δ 134.53-127.28 for the phenyl groups and at δ 33.27-30.91 for the CH2CH2
group. The ES-MS of this complex shows a peak for the molecular ion [M]+ at m/z
1916 and peaks corresponding to [Au(PPh3)2]+ at m/z 721 and [Au(PPh3)]+ at m/z 459.
68
Ru
Ph2P PPh2
PPh2Ph2P
Au(PPh3)C C C CC C C C(Ph3P)Au
Ru
Ph2P PPh2
PPh2Ph2P
HC C C CC C C CH
NaOMe2 eq AuCl(PPh3) 1:4 MeOH/THF
(1)
(15)
Scheme 58: Reaction scheme for the formation of 15
2.3.6.2. Reaction with Co3(µ3-CBr)(µ-dppm)(CO)7
As described in Section 2.3.5.2, a simple coupling reaction occurs between the
compound {TMS(C≡C)2}Au(PPh3) and the cobalt cluster Co3(µ3-CBr)(µ-dppm)(CO)7
in the presence of a Pd(0)/Cu(I) catalyst to afford the complex Co3{µ3-
C(C≡C)2TMS}(µ-dppm)(CO)7. Hence, the reaction of Co3(µ3-CBr)(µ-dppm)(CO)7
with Ru{C4[Au(PPh3)]}2(dppe)2 (15) at room temperature in THF in the presence of
the Pd(PPh3)4/Cu(I) catalyst mixture afforded trans-Ru{C5[Co3(µ-
dppm)(CO)7]}2(dppe)2 (16) as a bright orange solid in 54% yield. This reaction results
in elimination of two moles of Au(PPh3)Br and the formation of new C-C bonds
yielding a complex with two C5 carbon chains (Scheme 59).
69
Ru
Ph2P PPh2
PPh2Ph2P
C C Au(PPh3)(Ph3P)Au C C
Co(CO)2
Co(CO)3
CCo
Ph2P
PPh2
THF
Ru
Ph2P PPh2
PPh2Ph2P
C C C CC C C C
Co(CO)2
Co(CO)3
CCo
Ph2P
PPh2
(OC)2Co
Co(CO)3
C Co(CO)2
PPh2
Ph2P
(OC)2
(OC)2
CuI/Pd(PPh3)4
+
(16)
(15)
22Br
Scheme 59: Reaction scheme for the formation 16
Complex 16 was identified from its spectroscopic data. The infrared spectrum shows
ν(CO) bands in the terminal region and a ν(C≡C) band at 2084 cm-1. The 1H NMR
spectrum shows a broad multiplet at δ 7.48-6.82 due to the phenyl groups, two
multiplets at δ 2.68-2.56 and 2.32-2.19 assigned to the CH2 groups in dppe and two
multiplets at δ 4.45-4.40 and 3.54-3.48, which correspond to the two hydrogens of the
methylene group in the dppm ligands. In the 31P NMR spectrum, two resonances were
observed at δ 51.0 and 33.2, assigned to the phosphorus atoms of the dppe and dppm
ligands, respectively. In the 13C NMR spectrum, a multiplet at δ 221.31-206.21
indicates the presence of the CO groups and a multiplet at δ 134.56-126.55 shows the
presence of the phenyl groups. There are also two other multiplets for the dppm and
dppe ligands at δ 33.49-32.87 and 30.61-29.40, respectively.
2.3.6.3. Reaction with TCNE
TCNE is an electron-deficient alkene owing to the four electron-withdrawing cyano
groups. Cycloaddition of TCNE to RC≡CM triple bonds to give cyclobutenyl
complexes and subsequent ring-opening to buta-1,3-dien-2-yl complexes are
characteristic reactions of σ-alkynyl or σ-poly-ynyl ligands on transition metals.
These reactions proceed via intermediates which cannot be isolated in all cases, as the
cyclobutene undergoes rapid ring-opening.116,117 For example, the reaction of various
alkynyl complexes with TCNE are illustrated in Scheme 60.59,63
70
{LnM} C C {M'L'n'} {LnM} C C
C C
NCNC
CNCN
{M'L'n'}
{LnM} C C {M'L'n'}
C
CNNC
TCNE
C
NC CN
{MLn} = Fc, W(CO)3Cp
{M'L'n'} = Ru(dppm)Cp Ru(dppe)Cp Os(dppe)Cp Fc
Scheme 60: Cycloaddition of TCNE to {MLn}(C≡C){M’L’n’}
Consequently, TCNE is expected to react with the electron-rich regions of trans-
Ru(C4H)2(dppe)2 (1), possibly adding across one or both of the carbon-carbon triple
bonds. Addition of two equivalents of TCNE to a solution of 1 in dichloromethane
afforded bright purple solid Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17) in 93%
yield. It is reasonable to assume that this reaction goes via the formation of a
cyclobutene intermediate which is unstable and transforms rapidly to give the final
product 17 (Scheme 61).
Ru
Ph2P PPh2
PPh2Ph2P
HH C C C CC C C C
C C
NCNC CN
CN
CC CNCNNC
NC
Ru
Ph2P PPh2
PPh2Ph2P
C C CC C C
C
C
CNNC
C
NC
NC H
C
C
C
CN
CN
H
CNNC
CH2Cl2Ru
Ph2P PPh2
PPh2Ph2P
(C C) H(C C)H
Intermediate
22
(17)
TCNE
(1)
Scheme 61: Synthesis of 17
71
Complex 17 displayed expected resonances in the 1H, 31P and 13C NMR spectra. The 1H NMR spectrum contained a multiplet at δ 7.43-7.14 assigned to the aromatic
hydrogens of the phenyl groups, two multiplets at δ 3.08-2.99 and 2.25-2.17
corresponding to the hydrogens of -CH2CH2- and a singlet at δ 1.41 due to C-H. The 31P NMR spectrum shows only one peak at δ 47.4 which corresponds to the
phosphorus atoms of dppe. The 13C NMR spectrum shows the resonances for the
carbon atoms of the C4 chains and the resonances for two CN groups were found at δ
115.11 and 113.75 while the two other CN groups were found at δ 111.31 and 110.10.
In the infrared spectrum, one ν(C≡C) band at 1973 cm-1 and one ν(CN) band at 2220
cm-1 were observed. The ES-MS of 17 shows a peak for the molecular ion at m/z 1251
and peaks corresponding to [M - CN]+ at m/z 1225 and [Ru(dppe)2]+ at m/z 898.
Crystals of 17 were grown from a benzene/CH2Cl2 mixture and the molecular
structure was determined by single-crystal X-ray diffraction studies. These studies
confirmed that two molecules of TCNE react with the C≡C triple bonds furthest from
the ruthenium centre probably because of steric hindrance around the Ru(dppe)2
moiety.
The ORTEP diagram is shown in Figure 25 and selected bond distances and angles
are given in Table 5. The Ru-C(1) bond length of 2.002(8) Å is close to the value
expected for a ruthenium carbon single bond (2.01 Å) and the C(1)-C(2) bond length
of 1.24(1) Å confirms the presence of the C≡C triple bond. The C(2)-C(3) and C(3)-
C(4) distances of 1.40(1) Å and 1.47(1) Å respectively, are consistent with the
presence of C-C single bonds. The C(2)-C(3) bond length is shorter than expected
indicating that there is a small amount of electron delocalisation occurring. The angles
Ru-C(1)-C(2) [176.8(7) Å] and C(1)-C(2)-C(3) [178.2(8) Å] in 17 are nearly linear
whereas C(2)-C(3)-C(4) is bent [115.3(6) Å]. This angle can be explained by the
presence of the C(3)-C(30) and the C(4)-C(40) bonds which have typical C=C double
bond lengths.
72
Figure 25: ORTEP view of complex 17
Bond distances (Å) Bond Angles (o)
Ru-C(1) 2.002(8) Ru-C(1)-C(2) 176.8(7)
Ru-P(1) 2.392(2) P(1)-Ru-P(2) 82.64(7)
Ru-P(2) 2.385(2) P(1)-Ru-C(1) 90.9(2)
C(1)-C(2) 1.24(1) P(2)-Ru-C(1) 84.6(2)
C(2)-C(3) 1.40(1) C(1)-C(2)-C(3) 178.2(8)
C(3)-C(4) 1.47(1) C(2)-C(3)-C(4) 115.3(6)
C(30)-C(32) 1.45(1) C(3)-C(4)-C(40) 124.7(7)
C(3)-C(30) 1.38(1) C(30)-C(3)-C(4) 121.5(7)
C(4)-C(40) 1.35(1) C(3)-C(4)-C(40) 124.7(7)
Table 5: Selected bond distances (Å) and angles (o) for 17
73
trans-Ru(C4H)2(dppe)2
Ru{C4[Ru(dppe)Cp*]}2(dppe)2 Ru{C4[RuCp(PPh3)2]}2(dppe)2
Ru{C4[Ru(dppe)Cp]}2(dppe)2
2 RuCl(PPh3)2Cp
2 RuCl(dppe)Cp
2 RuCl(dppe)Cp*
Ru{C4[Au(PPh3)]}2(dppe)2
2 AuCl(PPh3)
Ru{C5[Co3(µ-dppm)(CO)7]}2(dppe)2
2 Co3(µ3-CBr)(µ-dppm)(CO)7
2 Tcne
Ru{C CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2
(2)
(1)
(17)
(3)
(4)
(15)
(16)
Figure 26: Summary of products synthesised from trans-Ru(C4H)2(dppe)2 (1)
74
Ru(C4H)2(dppe)2Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2
RuCl(PPh3)2Cp
RuCl(dppe)Cp
RuCl(dppe)Cp*
AuCl(PPh3)
Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2
Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2
RuCl(dppe)Cp
Co3(µ3-CBr)(µ-dppm)(CO)7
Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2
Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2
Ru{C4[Ru(dppe)Cp]}{C4[Au(PPh3)]}(dppe)2
Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2
Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2
Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2RuCl(dppe)Cp
AuCl(PPh3)
AuCl(PPh3)
(8)
(5)
(11)
(14)
(1)
(7)
(9)
(13)
(6)
(12)
Figure 27: Summary of products synthesised from trans-Ru(C4H)2(dppe)2 (1)
75
2.3.7. Synthesis of trinuclear copper(I) and silver(I) alkynyl complexes
In 1993, Gimeno and co-workers reported the synthesis and crystal structures of
various triangular copper(I) alkynyls such as [Cu3(µ-dppm)3(µ3-η1-C≡CR)2][BF4]
(where R = Ph, tBu, CH2OCH3) (Figure 28).118
CuC CCu
Cu
PP
PPP
P
CC RR
[BF4]
R = Ph, tBu, CH2OCH3
Figure 28: First examples of triangular copper(I) alkynyls
Since then, a number of polynuclear copper(I) and silver(I) alkynyl complexes have
been reported.119-125 They are promising building blocks for the construction of rigid-
rod oligomeric and polymeric materials and exhibit interesting properties such as
luminescence and an ability to mediate electron delocalisation. The trinuclear
copper(I) or silver(I) clusters can be capped by either organic alkynyl fragments
(Figure 29)126 or metal alkynyl fragments (Figure 30).127
MC CM
M
PP
PPP
P
CC RRM = Cu, Ag
+
R = Ph, C6H4-NO2-4, C6H4-OCH3-4
Figure 29: Examples of complexes capped with organic alkynyl fragments
76
MC C C CM
M
PP
PPP
P
CCCC Re
OC CO
CO
N N
Re
OC CO
N N
OC
M = Cu, Ag
+
Figure 30: Examples of complexes capped with metal alkynyl fragments
One method for the synthesis of copper(I) and silver(I) alkynyl complexes of this type
involves the reaction of three equivalents of [M2(µ-dppm)2(NCMe)2][X]2 (M = Cu,
Ag; X = PF6, BF4) with four equivalents of a terminal alkynyl group, in the presence
of an excess of KOH in CH2Cl2/MeOH.127 The complexes [Cu3(µ-dppm)3{µ3-η1-
C≡C(C6H2R2)nC≡C-p-Re(NN)(CO)3}2]+ (NN = bpy, tBu2bpy; R = H, Me; n = 0, 1)
were synthesised by this method (Scheme 62).127
MeCN Cu
P
P
Cu
P
P
NCMe OC Re C C
N N
OC CO
C C H
R
R
KOH
OC Re C C
N N
OC CO
C C
R
R
ReCC
NN
COOC
R
R
Cu CC
Cu
Cu
PP
PP
P
PCO
2+
3 4+
n
+
R = H, n = 1, NN = bpyR = Me, n = 1, NN = bpyR = H, n = 1, NN = tBu2bpyn = 0, NN = bpy
nn
Scheme 62: Synthesis of [Cu3(µ-dppm)3{µ3-η1-C≡C(C6H2R2)nC≡C-p-Re(NN)(CO)3}2]+
77
Similarly, the trinuclear copper(I) alkynyl complex [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-
dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6] (18) was synthesised from the mixture of
Ru(C≡CC≡CH)(dppe)Cp* and [Cu2(µ-dppm)2(NCMe)2][PF6]2. The reagents were
refluxed in an 4:1 THF/NEt3 mixture in the presence of a strong base (Scheme 63).12
CuC C C CRuPh2P PPh2
Cu
Cu
PP
PPP
P
CCCC RuPPh2Ph2P
HC C C CRu
Ph2P PPh2
[Cu2(µ-dppm)2(NCMe)2][PF6]2
THF/NEt3 dbu
∆
+
(18)
[PF6]
Scheme 63: Synthesis of 18
Following this work, the binuclear copper(I) complex [Cu2(µ-dppm)2(NCMe)2][BF4]2
would react similarly to give the [BF4]- analogue. Hence, Ru(C≡CC≡CH)(dppe)Cp*
was reacted with [Cu2(µ-dppm)2(NCMe)2][BF4]2 in 4:1 THF/NEt3 in the presence of
dbu and afforded the complex [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-
dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (19) as a bright yellow complex in 55% yield.
Complex 19 was readily identified from its spectroscopic data and elemental analysis.
It shows similar characteristics to complex 18; all data are summarised in Table 6.
The characteristic peaks for the Ru(dppe)Cp* and the dppm ligands are present in the 1H, 31P and 13C NMR spectra of 19. The difference between both complexes 18 and 19
is the presence of a different anion. Thus, the infrared spectrum of 19 shows one band
at 1059 cm-1 due to ν(BF) and the 31P NMR spectrum of 19 is missing the septet for
the phosphorus nuclei on [PF6]-.
78
Furthermore, the two compounds [Ag2(µ-dppm)2(NCMe)2][PF6]2 and [Ag2(µ-
dppm)2(NCMe)2][BF4]2 are readily available128 and they should react similarly to the
copper analogues to give new bis-ruthenium complexes linked by a silver cluster.
The complexes Ru(C≡CC≡CH)(dppe)Cp* and [Ag2(µ-dppm)2(NCMe)2][X]2 (X = PF6
or BF4) were refluxed in a 4:1 THF/NEt3 solvent mixture for one hour in presence of
dbu and in the dark. The two complexes [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-
dppm)3}(C≡C)2{Ru(dppe)Cp*}][X] (X = PF6 (20); BF4 (21)) were obtained in 53%
and 51% yields, respectively (Figure 31).
AgC C C CRuPh2P PPh2
Ag
Ag
PP
PPP
P
CCCC RuPPh2Ph2P
+
Figure 31: Representation of 20 and 21
Complexes 20 and 21 were characterised by IR, 1H, 31P, 13C NMR, ES-MS and
microanalysis. All the data are summarised in Table 6. The characteristic peaks for
the Ru(dppe)Cp* and the dppm ligands are present in the 1H, 31P and 13C NMR
spectra of 20 and 21. In the 31P NMR spectrum of 20, a septet is also present at δ -
141.05 (1JPF 711 Hz) for the phosphorus nuclei on PF6. The IR spectra of both
complexes contain ν(C≡C) bands and complex 20 has a band at 838 cm-1 for ν(PF)
while complex 21 has one ν(BF) band at 1052 cm-1.
79
Table 6: Spectroscopic data for complexes 18 - 21
Complex
IR (cm-1)
1H NMR (δ)
13C NMR (δ)
31P NMR (δ)
ES-MS (m/z)
[Ref]
18 2015 ν(C≡C) (w); 839 ν(PF) (s)
7.16-6.77 (m, 100H, Ph); 3.64-3.52 (m, 6H, dppm); 3.15-3.02, 2.89-2.54 (2 x m, 2 x 4H, CH2CH2); 1.84 (s, 30H, Cp*)
137.10-128.03 (m, Ph) ; 121.79 (t, 2J(CP) = 21 Hz, C1); 118.09 (s, C2); 95.01 (s, C3); 94.55 (s, C5Me5); 65.30 (s, C4); 28.20 (m, CH2CH2); 11.45 (s, C5Me5)
-140.7 (sept, 1JPF 710 Hz, PF6) -7.2 (s, 6P, dppm) 79.4 (s, 4P, dppe)
1355 [M + H]2+
635 [Ru(dppe)Cp*]+
12
19 2021 ν(C≡C)
(w); 1059 ν(BF) (s)
7.17-6.81 (m, 100H, Ph); 3.17-3.14 (m, 6H, dppm); 3.17-3.04, 2.87-2.56 (2 x m, 2 x 4H, CH2CH2); 1.56 (s, 30H, Cp*)
137.10-128.03 (m, Ph); 121.50 (t, 2J(CP) = 21 Hz, C1); 117.15, 95.01, 64.80 (s, C2, C3, C4); 94.19 (s, C5Me5); 28.20-27.96 (m, CH2CH2); 11.45 (s, C5Me5).
-7.3 (s, 6P, dppm) 79.4 (s, 4P, dppe)
1355 [M + H]2+
635 [Ru(dppe)Cp*]+
This work
20 2033 ν(C≡C)
(w); 838 ν(PF) (s)
7.90-6.87 (m, 100H, Ph); 3.25-3.22 (m, 6H, dppm); 2.55-2.51, 1.84-1.77 (2 x m, 2 x 4H, CH2CH2); 1.59 (s, 30H, Cp*)
133.61-127.82 (m, Ph); 123.55, 116.45, 95.79, 51.64 (s, C1, C2, C3, C4); 94.21 (s, C5Me5); 28.71-28.15 (m, CH2CH2); 9.83 (s, C5Me5)
-141.1 (sept, 1JPF 711 Hz, PF6) -1.3 (s, 6P, dppm) 80.7 (s, 4P, dppe)
1421 [M]2+
635 [Ru(dppe)Cp*]+
This work
21 2015 ν(C≡C)
(w); 1052 ν(BF) (s)
7.37-6.79 (m, 100H, Ph); 3.12-3.02 (m, 6H, dppm); 2.59-2.53, 1.87-1.79 (2 x m, 2 x 4H, CH2CH2); 1.56 (s, 30H, Cp*)
133.78-127.97 (m, Ph); 123.62, 116.57, 95.88, 51.72 (s, C1, C2, C3, C4); 94.20 (s, C5Me5); 28.94-28.86 (m, CH2CH2); 9.97 (s, C5Me5)
-1.2 (s, 6P, dppm) 80.5 (s, 4P, dppe)
1421 [M]2+
635 [Ru(dppe)Cp*]+
This work
80
2.4. Electrochemistry
2.4.1. trans-Ru{C4[Ru]}2(dppe)2 complexes
Due to their interest as possible models for molecular wires, the electronic properties
of complexes 2, 3, and 4 were examined. Density-functional theory (DFT) molecular
orbital calculations were performed on the model complex
Ru{C≡CC≡C[Ru(dHpe)Cp]}2(dHpe)2 [dHpe = H2P(CH2)2PH2].129 The HOMOs
consists of four closely spaced orbitals and there is a large energy gap between the
LUMO and the HOMO of 1.60 eV (Figure 34). It was deduced that eight electrons
could be lost from the HOMOs in a stepwise fashion. Using DFT calculations, a
contour plot of the HOMO and HOMO-1 of the model complex was prepared (Figure
32 and Figure 33).129 The HOMOs extend across the entire eleven-atom chain. An
important consequence of this is that any oxidation process cannot be expected to
occur solely at the metal centres but rather is delocalised across the entire chain.
Figure 32: Contour plot of the HOMO of the model complex
Figure 33: Contour plot of the HOMO-1 of the model complex
81
Figure 34: Partial orbital interaction diagram for the model complex
As mentioned previously, a convenient way to evaluate the electronic communication
in such systems is by using cyclic voltammetry. The cyclic voltammograms of
complexes 2, 3 and 4 were measured in CH2Cl2 under similar conditions, provided in
the general experimental conditions.
The cyclic voltammogram of trans-Ru{C4[Ru(dppe)Cp*]}2(dppe)2 (2) shows four
one-electron oxidation waves which are diffusion controlled. The first three waves at -
0.72 V, -0.33 V and +0.21 V are fully-reversible (ia/ic = 1) while a fourth is observed
at +0.70 V, which is partially reversible (ia/ic = 0.6). A fifth wave is present at +0.99
V but can not be assigned due to the preceding partially reversible wave at +0.70 V
(Figure 35). From the DFT calculations, it was deduced that eight electrons could be
lost from the HOMOs in a stepwise fashion. However, only five waves are present in
the cyclic voltammogram because the presence of the solvent front does not allow
further analysis. The differences between successive oxidation potentials ∆Eo are
significant, with values greater than 290 mV (for example, ∆E1/2 = 390 mV).58 This
indicates that there are strong interactions between the metal centres via the carbon
bridge and also that complex 2+ can be classified as a Class III complex by the Robin
and Day classification system.69
82
The cyclic voltammograms of trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2 (3) and trans-
Ru{C4[Ru(PPh3)2Cp]}2(dppe)2 (4) show a very similar pattern to that of complex 2.
Complexes 3 and 4 each show five waves at -0.70 V, -0.25 V, +0.47 V, +0.76 V,
+1.19 V and -0.64 V, -0.12 V, +0.49 V, +0.79 V, +1.26 V, respectively. Complexes 3
and 4 show large peak-to-peak separation with large values of ∆E1/2 of 450 mV for 3
and 520 mV for 4. Hence, complex 3+ and 4+ can be classified as class III complexes
by the Robin and Day classification system.69 Electrochemical data for complexes 2, 3
and 4 are summarised in Table 7.
The successful synthesis of 3 and 4 allows the generation of a series of symmetric
trinuclear complexes of general formula [Ru]-C≡CC≡C-Ru(dppe)2-C≡CC≡C-[Ru].
This allows the direct comparison of their redox properties and to determine the effect
of the exchange of the Ru(dppe)Cp* end-group for a Ru(dppe)Cp or Ru(PPh3)2Cp
moiety (For comparison all CVs were measured using the same potentiostat and cell
setup). From the data summarised in Table 7, it can be noticed that the oxidation
potentials of complex 2 are lower than these of 3 and 4. Hence, complex 2 is more
easily oxidised than complexes 3 and 4. It is also worth mentioning that the oxidation
potentials of complex 3 are intermediate to those observed for 2 and 4. It can also be
deduced that complex 3 will be more easily oxidised compared to complex 4. These
results are consistent with previous theoretical studies which found that the more
electron donating ligand Ru(dppe)Cp* will allow easier oxidation than the less
electron donating groups Ru(dppe)Cp and Ru(PPh3)2Cp. For example, the oxidation
potentials for the related series of diyndiyl complexes of general formula
[Ru](C≡CC≡C)[Ru] are shown in Table 7.12,59
Hence, it can be concluded that the ruthenium(II) moiety Ru(dppe)2 is strongly
electron-donating and acts as a conductor in these three complexes and the -C≡CC≡C-
bridge is very efficient in allowing electronic communication between the terminal
ruthenium groups. Complexes 2, 3 and 4 can therefore be proposed as possible
precursors for molecular wires. This study confirmed the previous research reported
for the complex trans-[Ru(C≡CC≡CFc)2(dppe)2] which found that the Ru(dppe)2
moiety allows electronic communication in this complex. (See Introduction)
83
Figure 35: Cyclic voltammogram of 2
84
In addition, a series of {Cp*(dppe)Ru}-(C≡C)n-{Ru(dppe)Cp*} (n = 1 - 8) complexes
were recently prepared and their cyclic voltammograms were recorded in order to
investigate the influence of chain length on the electronic interactions between two
ruthenium centres.12,55 The separation of the first two waves (∆E1/2) was considered
the best indication of the extent of interactions between the two redox centres.58 Table
7 summarises the values obtained for the various complexes {Cp*(dppe)Ru}-(C≡C)n-
{Ru(dppe)Cp*} (n = 2 - 5). It was deduced that as the chain length is increased, the
interactions between the two ruthenium centres decrease at a steady rate. This trend is
represented graphically in Figure 36, which is a plot of ∆E1/2 against chain length.
Hence, the comparison of the electronic properties of the bis(diyndiyl) ruthenium
complex 2 with these straight chain complexes was investigated. It was found that the
∆E1/2 value of complex 2 is between those of {Cp*(dppe)Ru}-(C≡C)3-
{Ru(dppe)Cp*} and {Cp*(dppe)Ru}-(C≡C)4-{Ru(dppe)Cp*} complexes. Therefore,
it can be concluded that the insertion of the Ru(dppe)2 unit in the C8 carbon chain of
complex 2 has increased the electronic interactions between the two ruthenium
centres compared to the complex with a straight C8 chain.
Figure 36: Chain length effect on ∆E1/2 in the {Cp*(dppe)Ru}2(C≡C)n series
85
2.4.2. trans-Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 complexes
As seen previously, the electronic properties associated with the trinuclear complexes
2, 3 and 4 were of interest. Therefore, the analysis of the cyclic voltammetry
associated with asymmetric complexes of general formula trans-
Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 (where [Ru] = Ru(dppe)Cp* (8) or
Ru(PPh3)2Cp (9)) was also investigated to compare the differences in electronic
properties.
The cyclic voltammograms of 8 and 9 were acquired. Five redox events are present
and are diffusion controlled. Complexes 8 and 9 each show three fully-reversible
waves at -0.70 V, -0.34 V, +0.15 V and -0.52 V, -0.14 V, +0.46 V, respectively. Two
partially reversible waves are also present at +0.59 V, +0.83 V and +0.73 V, +1.15 V,
respectively (Figure 37). All the values are summarised in Table 7. Furthermore, the
∆E1/2 values were found to be equal to 360 mV and 380 mV for 8 and 9 respectively.
These are significant values and indicate that there are strong interactions between the
metal centers. Hence, complex 8+ and 9+ can be classified as Class III complexes by
the Robin and Day classification system.69
The electronic properties of complexes 8 and 9 are very interesting compared to the
values obtained for the other trinuclear complexes 2, 3 and 4. By comparing the
oxidation potentials, it can be deduced that the first and second oxidation potentials of
8 are similar to these obtained for 2 and 3 whereas the E3 and E4 values of 8 are lower.
In the case of 9, the oxidation potentials E3 and E4 are very close to the values of the
complexes 3 and 4. This could be explained by the fact that complexes 8 and 9 are
made of a combination of the different end-group ligands and should therefore show
similarities in their electronic properties. This was also reported from the synthesis of
complexes {Cp(PPh3)2Ru}(C≡CC≡C){Ru(dppe)Cp} and
{Ru(PPh3)2Cp}(C≡CC≡C){Ru(dppe)Cp*} which was found to have oxidation
potentials very comparable to the three complexes {Ru(dppe)Cp*}2(C≡CC≡C),
{Ru(dppe)Cp}2(C≡CC≡C) and {Ru(PPh3)2Cp}2(C≡CC≡C) (Table 7).12,59
86
Complex E1 E2 E3 E4 E5 ∆E1/2 [Ref] 2 -0.72 -0.33 +0.21 +0.70 +0.99 0.39 This work 3 -0.70 -0.25 +0.47 +0.76 +1.19 0.45 This work 4 -0.64 -0.12 +0.49 +0.79 +1.26 0.52 This work 8 -0.70 -0.34 +0.15 +0.59 +0.83 0.36 This work 9 -0.52 -0.14 +0.46 +0.73 +1.15 0.38 This work {Ru(dppe)Cp*}2{C4} -0.43 +0.22 +1.04 +1.54a 0.65 12 {Ru(dppe)Cp}2{C4} -0.24 +0.35 +1.08 +1.44 0.59 59 {Ru(PPh3)2Cp}2{C4} -0.23 +0.41 +1.03 +1.68 0.64 59 {Cp(PPh3)2Ru}{C4}{Ru(dppe)Cp} -0.22 +0.42 +1.07 +1.52 0.64 59 {Cp(PPh3)2Ru}{C4}{Ru(dppe)Cp*} -0.33 +0.34 +1.04 +1.55 0.67 59 {Ru(dppe)Cp*}2{C6} -0.15 +0.33 +1.05 +1.33 0.48 12 {Ru(dppe)Cp*}2{C8} +0.08 +0.43 +1.07 +1.27 0.35 12 {Ru(dppe)Cp*}2{C10} +0.18 +0.45 +1.11 0.26 55
Table 7: Electrochemical data (V), a Peak potential of an irreversible process
87
Figure 37: Cyclic voltammogram of 8
88
2.4.3. trans-Ru{C4[Ru]}{C4H}(dppe)2 complexes
Electrochemical studies of the asymmetric complexes trans-
Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5), trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2
(6) and trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) were also completed. The
cyclic voltammograms of 5, 6 and 7 show two partially reversible waves and an
irreversible wave at ca 1.0 V (Figure 38). Due to the presence of the first partially
reversible wave it is not possible to calculate the ∆E1/2 values for the three complexes
and therefore assign them a classification.
Figure 38: Cyclic Voltammogram of 5
2.4.4. trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2
The electrochemical properties of complex trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2
(10) using cyclic voltammetry were investigated. The cyclic voltammogram of 10 is
composed of one partially reversible wave at +0.64 V followed by two undefined
waves (Figure 39). Due to the presence of the first partially reversible wave it is not
possible to assign the following waves, which maybe the result of decomposition of
the primary redox product.
89
Figure 39: Cyclic voltammogram of 10
2.4.5. Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2
The redox potentials for Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17) were
measured using cyclic voltammetry. The cyclic voltammogram of 17 shows that the
complex undergoes two oxidation-reduction processes which are diffusion controlled
(Figure 40). The two redox potentials occurring at -0.65 V and +1.21 V are partially
reversible (ia/ic = 0.6 and 0.8, respectively). The reduction at -0.65 V could
correspond to the C-CN groups, which are the most electronegative region of the
complex. The potential at +1.21 V is the oxidation of the Ru(dppe)2 moiety which is
at high potential probably due to the addition of the strongly electron-withdrawing CN
groups to the chain.
Figure 40: Cyclic voltammogram of 17
90
2.4.6. [{Cp*(dppe)Ru}(C≡C)2{M3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][X] (M = Cu,
Ag; X = PF6, BF4)
Density-functional theory (DFT) calculations were made on the model complex
[{Cp(dHpe)Ru}(C≡C)2{M3(µ-dHpm)3}(C≡C)2{Ru(dHpe)Cp}]+ where the dppm,
dppe and Cp* ligands have been replaced by the dHpm, dHpe and Cp ligands for
clarity.130 It was found that there are large energy gaps between the HOMO and the
LUMO of 2.322 eV and 2.288 eV for the copper(I) and the silver(I) complexes,
respectively (Figure 41). Furthermore, contour plots of the HOMO and HOMO-1
orbitals show that these orbitals are delocalised over the entire Ru-C4-M3-C4-Ru chain
(Figure 42 and Figure 43). This suggests that there will be some communication
between the ruthenium end-groups across the copper(I) and silver(I) clusters.130
Figure 41: Partial orbital interaction diagram for the model complex
91
Figure 42: Contour plot of the HOMO of the model complex
Figure 43: Contour plot of the HOMO-1 of the model complex In order to evaluate the electronic properties, the cyclic voltammograms of the
complexes [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (19)
and [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][X] (X = PF6 (20);
BF4 (21)) were measured in CH2Cl2 under similar conditions. The cyclic
voltammograms of complexes 19, 20 and 21 show two one-electron fully-reversible
oxidation waves (Figure 44). Their redox potentials are summarised in Table 9.
92
Figure 44: Cyclic voltammogram of 19 To this point, the separation of the first two waves (∆E) was considered the best
indication of the extent of interactions between the two redox centres. The difference
between successive oxidation potentials, ∆E1/2, for complex 19 is equal to 220 mV.
The distinction between Class II and Class III systems by the Robin and Day
classification is considered to be at 0.2 V,69 hence complex 19+ is slightly above it and
can be classified as a Class III complex. Therefore, it can be concluded that the
insertion of the trinuclear copper(I) cluster between the two diynyl fragments allow
electronic interactions between the metal termini.
The ∆E1/2 values of complexes 20 and 21 are 160 mV and 170 mV respectively. This
indicates that there are only minimal interactions between the two ruthenium termini
and complexes 20+ and 21+ can be classified as Class II complexes by the Robin and
Day classification system.69 Thus it appears that there is a decrease in the
communication when the trinuclear silver(I) cluster is present in the carbon chain.
93
Complex E1 E2 E3 E4 ∆E1/2 [Ref]
18 +0.15 +0.36 0.23 12
19 +0.17 +0.39 0.22 This work
20 +0.26 +0.43 0.16 This work
21 +0.29 +0.46 0.17 This work
{Ru(dppe)Cp*}2{C8} +0.08 +0.43 +1.07 +1.27 0.35 12
Table 8: Electrochemical data (V)
Therefore it can be deduced that the copper(I) cluster mediates reasonable interactions
between the two ruthenium termini over the carbon chain while the silver(I) cluster
diminishes significantly the ability of electronic communication. This could be
explained by the difference in the contribution to the HOMOs of the copper(I) and the
silver(I) complexes.
Furthermore, the separation of the first two waves (∆E1/2) of complexes 19, 20 and 21
are smaller than the value of the {Cp*(dppe)Ru}-(C≡C)4-{Ru(dppe)Cp*}complex.
Thus, the strength of electronic interactions decreases when the trinuclear copper(I) or
silver(I) clusters are inserted in the chain and makes these complexes less efficient
than a complex with a C8 carbon chain. These results further confirm that the insertion
of a copper(I) or silver(I) cluster makes the oxidation process more difficult and they
are therefore not good linkers for the synthesis of molecular wires.
94
2.5. Conclusions
In summary, symmetric and asymmetric bis(diyndiyl) ruthenium(II) complexes have
been successfully synthesised. It was shown that it is possible to build complexes
containing a Ru(dppe)2 moiety as the central linking group of two butadiyndiyl carbon
chains with metal ligand end-groups. Trans-Ru{C4[Ru]}2(dppe)2 (where [Ru] =
Ru(dppe)Cp* (2), Ru(dppe)Cp (3) and Ru(PPh3)2Cp (4)) and trans-
Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 (where [Ru] = Ru(dppe)Cp* (8) and
Ru(PPh3)2Cp (9)) have been successfully prepared and characterised
spectroscopically.
These complexes have been shown by cyclic voltammetry to undergo a series of five
stepwise one-electron oxidation processes. It was also established that strong
interactions exist between the ruthenium centres with a large separation in the
oxidation waves. The electrochemical studies also confirmed that the Ru(dppe)2 linker
is an effective communicator of electronic information from one termini to the other.
Hence, these bis(diyndiyl) ruthenium (II) compounds may be considered as models
for molecular wires and 2+, 3+, 4+, 8+, 9+ may be classified as Class III complexes by
the Robin-Day classification system.
The synthesis of trans-Ru{C4[Ru]}{C4H}(dppe)2 (where [Ru] = Ru(dppe)Cp* (5),
Ru(dppe)Cp (6) and Ru(PPh3)2Cp (7)) complexes has allowed the synthesis of
asymmetric complexes of general formula trans-
Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 (where [Ru] = Ru(dppe)Cp* (8) and
Ru(PPh3)2Cp (9)) and trans-Ru{C4[Ru]}{C4[Au(PPh3)]}(dppe)2 (where [Ru] =
Ru(dppe)Cp* (11), Ru(dppe)Cp (12) and Ru(PPh3)2Cp (13)). The insertion of the
Au(PPh3) fragment has enabled access to a complex with an extended carbon chain.
For example, complex 11 was further reacted with the cobalt cluster Co3(µ3-CBr)(µ-
dppm)(CO)7 to give complex 14 containing both an even- and odd-numbered alkynyl
linkages. Similar complexes could be prepared using the two complexes 12 and 13.
95
In the same way, the gold reaction between trans-Ru(C4H)(dppe)2 (1) and AuCl(PPh3)
was shown to occur readily and afforded the novel complex trans-
Ru{C4[Au(PPh3)]}2(dppe)2 (15). The reaction of 15 with Co3(µ3-CBr)(µ-dppm)(CO)7
gave a complex with longer carbon chains (C5). It is noteworthy that further reactions
can be performed with complex 15 as Au(PPh3) is a good leaving group.
The reaction of trans-Ru(C4H)(dppe)2 (1) with TCNE afforded the complex
Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17) in very good yield. The X-ray
crystal study of 17 has confirmed that it is the second C≡C triple bond out from the
ruthenium centre which is attacked by TCNE as a result of the steric protection of the
inner C≡C bond by the two bulky dppe ligands. It was also shown that the C4 carbon
chains are bent in this complex due to the presence of the double bonds.
Furthermore, the syntheses of three copper(I) and silver(I) alkynyl complexes of
general formula [{Cp*(dppe)Ru}(C≡C)2{M3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][X]
(where M = Cu, Ag and X = PF6, BF4) 19, 20 and 21 were successfully achieved. The
electronic communication in such complexes was evaluated through the use of cyclic
voltammetry. The studies have shown that electronic communication exists between
the two ruthenium centres when a trinuclear copper(I) or a silver(I) cluster is present,
but the electronic interactions become weak.
96
2.6. Experimental
General experimental conditions are detailed on page viii. Reagents: The compounds trans-Ru(C4H)2(dppe)2,131 RuCl(dppe)Cp*,132 RuCl(dppe)Cp,133
RuCl(PPh3)2Cp,134 Ru(C≡CC≡CH)(dppe)Cp*,30 trans-[RuCl(dppe)2]OTf,105 Co3(µ3-
CBr)(µ-dppm)(CO)7,135 AuCl(PPh3),136 [Cu2(µ-dppm)2(MeCN)2][BF4]2,137 [Ag2(µ-
dppm)2(MeCN)2][PF6]2128, [Ag2(µ-dppm)2(MeCN)2][BF4]2
128 and Pd(PPh3)4,12 were
all prepared by standard literature methods. Na[BPh4], CuI, dbu and TCNE were used
as received from Sigma-Aldrich or Fluka.
trans-Ru{C4[Ru(dppe)Cp*]}2(dppe)2 (2)
To a suspension of trans-Ru(C4H)2(dppe)2 (1) (51 mg, 0.05 mmol), RuCl(dppe)Cp*
(70 mg, 0.1 mmol), Na[BPh4] (35 mg, 0.1 mmol) and NEt3 (0.02 mL, 0.1 mmol) was
added a 1:1 mixture of CH2Cl2/MeOH and the solution was heated at reflux point for
2 h. The solvent was then removed and the residue dissolved in a minimum amount
of CH2Cl2 and filtered through cotton wool into stirred hexane (40 mL). The yellow-
green precipitate was collected and washed with hexane to yield trans-
Ru{C4[Ru(dppe)Cp*]}2(dppe)2 (2) (76 mg, 67%). Anal. Calcd. (C132H126P8Ru3): C,
70.05; H, 5.61. Found: C, 70.01; H, 5.65. IR (CH2Cl2, cm-1): ν(C≡C) 2012 (m), 1969
(w). 1H NMR (CDCl3): δ 7.72-7.04 (m, 80H, Ph); 2.60-2.55, 1.91-1.82 (2 x m, 16H,
CH2CH2); 1.46 (s, 30H, Cp*). 13C NMR (CD2Cl2): δ 135.46-129.61 (m, Ph); 97.80 (s,
C5Me5); 31.49-31.15 (m, CH2CH2); 11.53 (s, C5Me5). 31P NMR (CDCl3): δ 76.3 (s,
RuCp*dppe); 53.4 (s, Ru(dppe)2). ES-MS (+ve ion, MeOH, m/z): 2266, [M]+; 898,
[Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+.
97
trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2 (3)
Similarly, the reaction between trans-Ru(C4H)2(dppe)2 (1) (50 mg, 0.05 mmol) and
RuCl(dppe)Cp (61 mg, 0.1 mmol) gave trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2 (3) as a
brown powder (32 mg, 75%). Anal. Calcd. (C122H106P8Ru3): C, 69.02; H, 5.03. Found:
C, 69.05; H, 5.09. IR (CH2Cl2, cm-1): ν(C≡C) 2124 (m), 2013 (w). 1H NMR (CDCl3):
δ 7.67-7.16 (m, 80H, Ph); 4.35 (s, 10H, Cp); 2.23-2.19, 1.91-1.79 (2 x m, 16H,
CH2CH2). 13C NMR (CD2Cl2): δ 136.27-129.37 (m, Ph); 83.85 (s, C5H5); 29.09-28.34
(m, CH2CH2). 31P NMR (CDCl3): δ 80.7 (s, Ru(dppe)Cp); 56.5 (s, Ru(dppe)2). ES-
MS (+ve ion, CH3CN, m/z): 2123, [M]+; 2122, [M - H]+; 898, [Ru(dppe)2]+; 606,
[Ru(NCMe)(dppe)Cp]+; 565, [Ru(dppe)Cp]+.
trans-Ru{C4[Ru(PPh3)2Cp]}2(dppe)2 (4)
Similarly, the reaction of trans-Ru(C4H)2(dppe)2 (1) (51 mg, 0.05 mmol) and
RuCl(PPh3)2Cp (75 mg, 0.1 mmol) gave trans-Ru{C4[Ru(PPh3)2Cp]}2(dppe)2 (4) as a
brown powder (33 mg, 77%). Anal. Calcd. (C142H118P8Ru3): C, 71.80; H, 5.01. Found:
C, 71.84; H, 5.04. IR (CH2Cl2, cm-1): ν(C≡C) 2014 (w), 1979 (w). 1H NMR (CDCl3):
δ 7.71-6.93 (m, 100H, Ph); 4.36 (s, 10H, Cp); 2.31-2.19, 1.93-1.80 (2 x m, 8H,
CH2CH2). 13C NMR (CD2Cl2): δ 133.88-127.14 (m, Ph); 83.10 (s, C5H5); 30.09-29.56
(m, CH2CH2). 31P NMR (CDCl3): δ 57.0 (s, Ru(dppe)2); 43.0 (s, Ru(PPh3)2). ES-MS
(+ve ion, CH3CN, m/z): 2375, [M]+; 1685, [Ru(PPh3)2CpC4Ru(dppe)2C4]+; 898,
[Ru(dppe)2]+; 691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.
trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5)
trans-Ru(C4H)2(dppe)2 (1) (50 mg, 0.05 mmol), RuCl(dppe)Cp* (34 mg, 0.05 mmol),
Na[BPh4] (17 mg, 0.05 mmol) and NEt3 (0.01 mL, 0.07 mmol) were combined and a
6:1 mixture of CH2Cl2/MeOH was added. The resulting suspension was heated at
reflux point for 1 h. The solvent was then removed and the resulting green residue
dissolved in a minimum amount of CH2Cl2 and filtered through cotton wool into
stirred hexane (40 mL). The precipitate was collected and washed with hexane to
98
yield trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5) as a green powder (66 mg, 80%).
Anal. Calcd. (C96H88P6Ru2): C, 70.75; H, 5.44. Found: C, 70.73; H, 5.54. IR (CH2Cl2,
cm-1): ν(≡CH) 3055 (m); ν(C≡C) 2022 (w), 1968 (w). 1H NMR (CDCl3): δ 7.99-7.12
(m, 60H, Ph); 2.47-2.44, 2.10-2.03 (2 x m, 12H, CH2CH2); 1.56 (s, 15H, Cp*); 1.44
(s, H). 13C NMR (CD2Cl2): δ 136.32-127.32 (m, Ph); 96.91 (s, C5Me5); 31.51-30.22
(m, CH2CH2); 10.64 (s, C5Me5). 31P NMR (CDCl3): δ 70.5 (s, Ru(dppe)Cp*); 46.1 (s,
Ru(dppe)2). ES-MS (+ve ion, MeOH, m/z): 1631, [M]+; 898, [Ru(dppe)2]+; 635,
[Ru(dppe)Cp*]+.
trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2 (6)
Similarly, from trans-Ru(C4H)2(dppe)2 (1) (51 mg, 0.05 mmol) and RuCl(dppe)Cp
(32 mg, 0.05 mmol) was obtained trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2 (6) as a
green powder (67 mg, 85%). Anal. Calcd. (C91H78P6Ru2): C, 70.08; H, 5.04. Found:
C, 70.11; H, 5.12. IR (CH2Cl2, cm-1): ν(≡CH) 3053 (w); ν(C≡C) 1995 (m), 1919 (m). 1H NMR (C6D6): δ 7.42-6.87 (m, 60H, Ph); 4.50 (s, 5H, Cp); 2.55-2.51, 2.11-2.04 (2
x m, 12H, CH2CH2); 1.41 (s, H). 13C NMR (CD2Cl2): δ 136.01-125.22 (m, Ph); 84.84
(s, C5H5); 30.54-29.27 (m, CH2CH2). 31P NMR (C6D6): δ 81.5 (s, Ru(dppe)Cp); 56.4
(s, Ru(dppe)2). ES-MS (+ve ion, CH3CN, m/z): 1560, [M]+; 898, [Ru(dppe)2]+; 605,
[Ru(NCMe)(dppe)Cp]+; 563, [Ru(dppe)Cp]+.
trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7)
Similarly, from trans-Ru(C4H)2(dppe)2 (1) (51 mg, 0.05 mmol) and RuCl(PPh3)2Cp
(37 mg, 0.05 mmol) was obtained trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) as a
brown powder (67 mg, 85%). Anal. Calcd. (C101H84P6Ru2): C, 71.96; H, 5.02. Found:
C, 72.03; H, 5.08. IR (CH2Cl2, cm-1): ν(≡CH) 3055 (w); ν(C≡C) 1981 (m), 1896 (m). 1H NMR (CDCl3): δ 7.76-6.91 (m, 70H, Ph); 4.20 (s, 5H, Cp); 2.39-2.37, 2.10-2.06 (2
x m, 8H, CH2CH2); 1.40 (s, H). 13C NMR (CD2Cl2): δ 133.97-125.72 (m, Ph); 81.48
(s, C5H5); 31.03-30.22 (m, CH2CH2). 31P NMR (CDCl3): δ 53.0 (s, Ru(dppe)2); 40.0
(s, (PPh3)2Cp). ES-MS (+ve ion, CH3CN, m/z): 1685, [M]+; 898, [Ru(dppe)2]+; 690,
[Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.
99
trans-Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2 (8)
To a suspension of trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5) (30 mg, 0.018
mmol), RuCl(dppe)Cp (17 mg, 0.027 mmol), Na[BPh4] (9.6 mg, 0.027 mmol) and
NEt3 (0.02 mL, 0.1 mmol) was added a 1:1 mixture of CH2Cl2/MeOH. The resulting
suspension was heated at reflux point for 1 h. The solvent was then removed and the
resulting residue dissolved in a minimum amount of CH2Cl2 and filtered through
cotton wool into stirred hexane (40 mL). The green precipitate was collected and
washed with hexane to yield trans-Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2
(8) (32 mg, 77%). Anal. Calcd (C127H116P8Ru3): C, 69.45; H, 5.33. Found: C, 68.98;
H, 5.33. IR (Nujol, cm-1): ν(C≡C) 2021 (m), 1961 (m). 1H NMR (CDCl3): δ 7.88-6.90
(m, 80H, Ph); 4.59 (s, 5H, Cp); 2.98-2.84, 2.24-2.16 (m, 16H, CH2CH2); 1.45 (s, 15H,
Cp*). 13C NMR (CD2Cl2): δ 134.82-127.03 (m, Ph); 99.92 (s, C5Me5); 81.76 (s,
C5H5); 30.82-29.97 (m, CH2CH2); 9.89 (s, C5Me5). 31P NMR (CDCl3): δ 80.7 (s,
Ru(dppe)Cp); 76.4 (s, Ru(dppe)Cp*); 55.6 (s, Ru(dppe)2). ES-MS (+ve ion, CH3CN,
m/z): 2194, [M + H]+; 1629, [M - Ru(dppe)Cp]+; 898, [Ru(dppe)2]+; 635,
[Ru(dppe)Cp*]+; 675, [Ru(NCMe)(dppe)Cp*]+; 565, [Ru(dppe)Cp]+; 605,
[Ru(NCMe)(dppe)Cp]+.
trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2 (9)
Similarly, trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2 (9) was obtained
from trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) (31 mg, 0.019 mmol),
RuCl(dppe)Cp (12 mg, 0.019 mmol) and Na[BPh4] (7 mg, 0.019 mmol) as a green
powder (33 mg, 78%). Anal. Calcd. (C132H112P8Ru3): C, 70.39; H, 5.02. Found: C,
69.81; H, 5.37. IR (Nujol, cm-1): ν(C≡C) 2017 (m), 1888 (w). 1H NMR (CDCl3): δ
7.87-6.93 (m, 75H, Ph); 2.71-2.57, 2.42-2.37 (2 x m, 12H, CH2CH2); 4.58 (s, 5H, Cp);
4.32 (s, 5H, Cp). 13C NMR (CD2Cl2): δ 135.47-128.56 (m, Ph); 81.25 (s, C5H5); 80.93
(s, C5H5); 30.10-29.20 (m, CH2CH2). 31P NMR (CDCl3): δ 80.7 (s, Ru(dppe)Cp); 55.9
(s, Ru(dppe)2); 42.9 (s, Ru(PPh3)2). ES-MS (+ve ion, CH3CN, m/z): 1685,
[Ru(PPh3)2CpC4Ru(dppe)2C4]+; 1559, [Ru(dppe)CpC4Ru(dppe)2C4]+; 898,
[Ru(dppe)2]+; 690, [Ru(PPh3)2Cp]+; 605, [Ru(NCMe)(dppe)Cp]+; 565 [Ru(dppe)Cp]+;
429, [Ru(PPh3)Cp]+.
100
trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 (10)
A mixture of Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.07 mmol) and [RuCl(dppe)2]OTf
(80 mg, 0.07 mmol) in a 1:1 CH2Cl2/NEt3 mixture was stirred at r.t. for 2 days. The
solvent was then removed and the yellow residue was washed with Et2O (40 mL) and
dried under vacuum to give trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 (10) as a pale
yellow powder (99 mg, 83%). Anal. Calcd. (C41H42P2Ru): C, 68.37; H, 5.43. Found:
C, 68.54; H, 5.40. IR (CH2Cl2, cm-1): ν(C≡C) 2037 (m), 1988 (w). 1H NMR (CDCl3):
δ 7.72-6.90 (m, 60H, Ph); 3.57-3.54, 3.49-3.46 (2 x m, 8H, CH2CH2); 2.86-2.76, 1.87-
1.75 (2 x m, 4H, CH2CH2); 1.50 (s, 15H, Cp*).13C NMR (CDCl3): δ 133.23-128.11
(m, Ph); 93.26 (s, C5Me5); 32.22-31.79 (m, CH2CH2); 9.82 (s, C5Me5). 31P NMR
(CDCl3): δ 82.8 (s, Ru(dppe)Cp*); 60.1 (t, 18Hz, dppe); 50.6 (t, 18Hz, dppe). ES-MS
(+ve ion, MeOH, m/z): 1615, [M - H]+; 898, [Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+.
trans-Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11)
To a solution of trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5) (50 mg, 0.04 mmol)
and NaOMe (3 mg, 0.15 mmol) in a 1:4 mixture of MeOH/THF was added
AuCl(PPh3) (15 mg, 0.03 mmol). The reaction mixture was stirred at r.t. for 3 h and
the solvent was then evaporated. The residue was dissolved in minimum amount of
CH2Cl2 and dropped into rapidly stirred hexane. The pale yellow precipitate was
collected by filtration, washed with hexane (2 x 20 mL) and air-dried to afford trans-
Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11) (55 mg, 70%). Anal. Calcd.
(C114H102AuP7Ru2): C, 65.58; H, 4.92. Found: C, 65.89; H, 5.20. IR (Nujol, cm-1):
ν(C≡C) 2012 (w), 1957 (m). 1H NMR (CDCl3): δ 7.69-7.04 (m, 75H, Ph); 3.52-3.15,
2.37-2.30 (2 x m, 12H, CH2CH2); 1.57 (s, 15H, Cp*). 13C NMR (CDCl3): δ 139.31-
121.36 (m, Ph); 98.80 (s, C5Me5); 30.63-29.65 (m, CH2CH2); 9.48 (s, C5Me5). 31P
NMR (CDCl3): δ 73.8 (s, Ru(dppe)Cp*); 55.3 (s, Ru(dppe)2); 44.6 (s, Au(PPh3)). ES-
MS (+ve ion, MeOH, m/z): 2086, [M]+; 2055 [M - P]+; 1626, [M - Au(PPh3)]+.
101
trans-Ru{C4[Ru(dppe)Cp]}{C4[Au(PPh3)]}(dppe)2 (12)
Similarly, from trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2 (6) (40 mg, 0.03 mmol) and
AuCl(PPh3) (13 mg, 0.03 mmol) was obtained the pale yellow powder trans-
Ru{C4[Ru(dppe)Cp]}{C4[Au(PPh3)]}(dppe)2 (12) (33 mg, 62%). Anal. Calcd.
(C109H93AuP7Ru2): C, 64.85; H, 4.64. Found: C, 65.13; H, 5.11. IR (CH2Cl2, cm-1):
ν(C≡C) 2013 (w), 1882 (w). 1H NMR (CDCl3): δ 7.87-6.91 (m, 75H, Ph); 4.57 (s,
5H, Cp); 2.56-2.49, 2.33-2.24 (2 x m, 12H, CH2CH2). 13C NMR (CDCl3): δ 142.68-
122.00 (m, Ph); 84.97 (s, C5H5); 30.83-29.79 (m, CH2CH2). 31P NMR (CDCl3): δ 80.7
(s, Ru(dppe)Cp); 53.3 (s, Ru(dppe)2); 44.6 (s, Au(PPh3)). ES-MS (+ve ion, MeOH,
m/z): 2018, [M]+; 898, [Ru(dppe)2]+; 565 [Ru(dppe)Cp]+.
trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2 (13)
Similarly, trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2 (13) was obtained
from trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) (41 mg, 0.03 mmol) and
AuCl(PPh3) (13 mg, 0.03 mmol) as a pale yellow powder (36 mg, 69%). Anal. Calcd.
(C119H99P7AuRu2): C, 66.63; H, 4.65. Found: C, 66.95; H, 5.22. IR (CH2Cl2, cm-1):
ν(C≡C) 1970 (w), 1899 (w). 1H NMR (CDCl3): δ 7.79-6.86 (m, 85H, Ph); 4.36 (s,
75H, Cp); 2.30-2.25, 1.99-1.88 (2 x m, 8H, CH2CH2). 13C NMR (CDCl3): δ 136.01-
121.85 (m, Ph); 84.05 (s, C5H5); 31.12-29.25 (m, CH2CH2). 31P NMR (CDCl3): δ 53.9
(s, Ru(dppe)2); 51.4 (s, Ru(PPh3)2Cp); 43.2 (s, Au(PPh3)). ES-MS (+ve ion, MeOH,
m/z): 2113, [M - P]+; 2038, [M - PPh]+; 898, [Ru(dppe)2]+; 429, [Ru(PPh3)Cp]+.
trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2 (14)
Co3(µ3-CBr)(µ-dppm)(CO)7 (16 mg, 0.02 mmol), CuI (7 mg, 0.04 mmol), Pd(PPh3)4
(41 mg, 0.03 mmol) and trans-Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11) (41
mg, 0.02 mmol), were dissolved in THF (30 mL) and stirred at r.t. for 4 h. The
solution was filtered and the solvent was then evaporated. The brown residue was
then dissolved in acetone and filtered through cotton wool into stirred hexane (40
mL). The precipitate was collected and washed with hexane to afford trans-
102
Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2 (14) as a brown powder (15
mg, 33%). Anal. Calcd. (C129H109P8Ru2O7Co3): C, 64.61; H, 4.58. Found: C, 64.66;
H, 4.61. IR (CH2Cl2, cm-1): ν(CO): 2069 (m), 2058 (s); ν(C≡C) 2010 (w); 1978 (m). 1H NMR (CDCl3): δ 7.70-6.83 (m, 80H, Ph); 2.85-2.77, 2.55-2.45 (2 x m, 12H,
CH2CH2); 4.45-4.40 (m, H, CH2); 3.48-3.43 (m, H, CH2); 1.51 (s, 15H, Cp*). 13C
NMR (CDCl3): δ 203.29-200.02 (m, CO); 139.37-132.77 (m, Ph); 96.86 (s, C5Me5);
33.95-32.22 (m, CH2); 30.40-29.63 (m, CH2CH2); 10.11 (s, C5Me5). 31P NMR
(CDCl3): δ 72.8 (s, Ru(dppe)Cp*); 55.9 (s, Ru(dppe)2); 30.6 (s, dppm). ES-MS (+ve
ion, CH3CN, m/z): 2370, [M – CO]+; 898, [Ru(dppe)2]+; 675, [Ru(dppe)Cp*]+.
trans-Ru{C4[Au(PPh3)]}2(dppe)2 (15)
To a solution of trans-Ru(C4H)2(dppe)2 (1) (100 mg, 0.1 mmol) and NaOMe (28 mg,
0.5 mmol) in a 1:4 mixture of MeOH/THF was added AuCl(PPh3) (100 mg, 0.2
mmol). The reaction mixture was stirred at r.t. for 5 h. The bright yellow precipitate
was collected by filtration, washed with hexane (2 x 10 mL) and air-dried to afford
trans-Ru{C4[Au(PPh3)]}2(dppe)2 (15) (0.17 mg, 89%). Anal. Calcd.
(C96H78Au2P6Ru): C, 60.29; H, 4.11. Found: C, 60.31; H, 4.17. IR (CH2Cl2, cm-1):
ν(C≡C) 2084 (w), 1974 (m). 1H NMR (CDCl3): δ 7.61-7.07 (m, 60H, Ph); 3.76-3.59,
2.61-2.51 (2 x m, 8H, CH2CH2). 13C NMR (CDCl3): δ 134.53-127.28 (m, Ph); 33.27-
30.91 (m, CH2CH2). 31P NMR (CDCl3): δ 53.10 (s, Ru(dppe)2); 46.08 (s, Au(PPh3)).
ES-MS (+ve ion, MeOH, m/z): 1916, [M]+; 721, [Au(PPh3)2]+; 459, [Au(PPh3)]+.
trans-Ru{C5[Co3(µ-dppm)(CO)7]}2(dppe)2 (16)
Co3(µ3-CBr)(µ-dppm)(CO)7 (88 mg, 0.1 mmol), trans-Ru{C4[Au(PPh3)]}2(dppe)2
(15) (110 mg, 0.05 mmol), CuI (18 mg, 0.1 mmol) and Pd(PPh3)4 (137 mg, 0.1 mmol)
were dissolved in THF (50 mL) and stirred at r.t. for 4 h. The solution was filtered and
the solvent was evaporated to dryness. The residue was purified by column
chromatography on silica gel, eluted with a mixture of 3:7 acetone/hexane to afford a
bright orange powder trans-Ru{C5[Co3(µ-dppm)(CO)7]}2(dppe)2 (16) (70 mg, 54%).
103
Anal. Calcd. (C126H92P8RuO14Co6): C, 59.76; H, 3.66. Found: C, 59.84; H, 3.58. IR
(CH2Cl2, cm-1): ν(C≡C) 2084 (w); ν(CO) 2062 (w), 2057 (s), 2033 (m), 1999 (w). 1H
NMR (CDCl3): δ 7.48-6.82 (m, 80H, Ph); 4.45-4.40 (m, 2H, CH2); 3.54-3.48 (m, 2H,
CH2); 2.68-2.56, 2.32-2.19 (2 x m, 8H, CH2CH2). 13C NMR (CDCl3): δ 221.31-206.21
(m, CO); 134.56-126.55 (m, Ph); 33.49-32.87 (m, CH2); 30.61-29.40 (m, CH2CH2). 31P NMR (CDCl3): δ 51.0 (s, Ru(dppe)2); 33.2 (s, dppm). ES-MS (+ve ion, MeOH,
m/z): 2552, [M + Na]+; 2528, [M - H]+.
Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17)
To a solution of trans-Ru(C4H)2(dppe)2 (1) (50 mg, 0.05 mmol) in CH2Cl2 (40 ml)
was added TCNE (12 mg, 0.09 mmol) and the reaction mixture was stirred at r.t. for
16 h, gradually changing in colour from yellow to purple. The solvent was then
removed and the residue was dissolved in minimum amount of benzene and purified
by preparative TLC, eluted with CH2Cl2 to afford a bright purple powder
Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17) (52.2 mg, 93%) (Rf 0.32). Single
crystals suitable for X-ray studies were grown from CH2Cl2/benzene. Anal. Calcd
(C72H50P4RuN8): C, 69.00; H, 4.02; N, 8.95. Found: C, 68.97; H, 4.14; N, 8.86. IR
(CH2Cl2, cm-1): ν(CN) 2220 (m); ν(C≡C) 1973 (w). 1H NMR (CDCl3): δ 7.43-7.14
(m, 40H, Ph); 3.08-2.99, 2.25-2.17 (2 x m, 8H, CH2CH2); 1.41 (s, 2H, =CH). 13C
NMR (CDCl3): δ 152.78, 142.85, 126.12, 90.82 (s, C1, C2, C3, C4); 134.16-128.64 (m,
Ph); 115.11, 113.75 (2 x s, 2 x CN); 111.31, 110.10 (2 x s, 2 x CN); 30.61, 30.47 (2 x
s, 2 x C(CN)2); 30.47-29.98 (m, CH2CH2). 31P NMR (CDCl3): δ 47.4 (s, Ru(dppe)2).
ES-MS (+ve ion, MeOH, m/z): 1251, [M]+; 1225, [M - CN]+; 898, [Ru(dppe)2]+.
[{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (19) To a solution of Ru(C≡CC≡CH)(dppe)Cp* (57 mg, 0.08 mmol) in 4:1 THF/NEt3 (10
mL) was added dbu (35 mg, 0.23 mmol) followed by [Cu2(µ-dppm)2(MeCN)2][BF4]2
(73 mg, 0.06 mmol). The solution was heated at reflux for 1 h before cooling and
solvent was then removed. The product was extracted in CH2Cl2, loaded onto a basic
104
alumina column and eluted with a 4:6 acetone/hexane mixture. The solvent was then
removed and crystallisation from CH2Cl2/hexane gave bright yellow crystalline solid
that was collected and washed with Et2O to give [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-
dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (19) (88 mg, 55%). Anal. Calcd.
(C155H144Cu3BF4P10Ru2): C, 66.58; H, 5.19. Found: C, 66.85; H, 5.11. IR (Nujol, cm-
1): ν(C≡C) 2021 (w); ν(BF) 1059 (s). 1H NMR (C6D6): δ 7.17-6.81 (m, 100H, Ph);
3.17-3.14 (m, 6H, dppm); 3.17-3.04, 2.87-2.56 (2 x m, 2 x 4H, CH2CH2); 1.56 (s,
30H, Cp*). 13C NMR (C6D6): δ 137.10-128.03 (m, Ph); 121.50 (t, 2J(CP) = 21 Hz,
C1); 117.15, 95.01, 64.80 (s, C2, C3, C4); 94.19 (s, C5Me5); 28.20-27.96 (m, CH2CH2);
11.45 (s, C5Me5). 31P NMR (C6D6): δ -7.3 (s, 6P, dppm); 79.4 (s, 4P, dppe). ES-MS
(+ve ion, MeOH, m/z): 1355, [M + H]2+; 635, [Ru(dppe)Cp*]+.
[{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6] (20) To a solution of Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.08 mmol) in 4:1 THF/NEt3 (10
mL) was added dbu (35 mg, 0.23 mmol) followed by [Ag2(µ-dppm)2(MeCN)2][PF6]2
(77 mg, 0.06 mmol). The solution was heated at reflux for 1 h in the dark before
cooling and solvent was then removed. The residue was dissolved in acetone (5 mL)
and added to rapidly stirred Et2O (40 mL). A yellow precipitate was collected and
washed with Et2O to give [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-
dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6] (20) (90 mg, 53%). Anal. Calcd.
(C155H144Ag3F6P11Ru2): C, 62.32; H, 4.86. Found: C, 62.52; H, 5.02. IR (Nujol, cm-1):
ν(C≡C) 2033 (w); ν(PF) 838 (s). 1H NMR (C6D6): δ 7.90-6.87 (m, 100H, Ph); 3.25-
3.22 (m, 6H, dppm); 2.55-2.51, 1.84-1.77 (2 x m, 2 x 4H, CH2CH2); 1.59 (s, 30H,
Cp*). 13C NMR (C6D6): δ 133.61-127.82 (m, Ph); 123.55, 116.45, 95.79, 51.64 (s, C1,
C2, C3, C4); 94.21 (s, C5Me5); 28.71-28.15 (m, CH2CH2); 9.83 (s, C5Me5). 31P NMR
(C6D6): δ -141.1 (sept, 1JPF 711 Hz, PF6); -1.3 (s, 6P, dppm); 80.7 (s, 4P, dppe). ES-
MS (+ve ion, acetone, m/z): 1421, [M]2+; 635, [Ru(dppe)Cp*]+.
105
[{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (21) Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (55 mg, 0.08 mmol) with [Ag2(µ-
dppm)2(MeCN)2][BF4]2 (75 mg, 0.06 mmol) gave the mustard yellow complex
[{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (21) (90 mg,
51%). Anal. Calcd. (C155H144Ag3BF4P10Ru2): C, 63.56; H, 4.96. Found: C, 63.77; H,
4.60. IR (Nujol, cm-1): ν(C≡C) 2015 (w); ν(BF) 1052 (s). 1H NMR (C6D6): δ 7.37-
6.79 (m, 100H, Ph); 3.12-3.02 (m, 6H, dppm); 2.59-2.53, 1.87-1.79 (2 x m, 2 x 4H,
CH2CH2); 1.56 (s, 30H, Cp*). 13C NMR (C6D6): δ 133.78-127.97 (m, Ph); 123.62,
116.57, 95.88, 51.72 (s, C1, C2, C3, C4); 94.20 (s, C5Me5); 28.94-28.86 (m, CH2CH2);
9.97 (s, C5Me5). 31P NMR (C6D6): δ -1.2 (s, 6P, dppm); 80.5 (s, 4P, dppe). ES-MS
(+ve ion, acetone, m/z): 1421, [M]2+; 635, [Ru(dppe)Cp*]+.
Chapter Three
A New Method for the Synthesis of
Diyndiyl Ruthenium(II) Complexes
107
3.1. Introduction
As described in Chapter One, diyndiyl complexes have been synthesised by several
methods. Of interest to this work is one particular method which involves the
lithiation of terminal diynyl ligands with any of a range of organolithium bases, such
as n-, sec- or t-BuLi, or LDA, followed by treatment with a metal halide. The
lithiation of a terminal diynyl complex with a lithium base results in the formation of
a nucleophilic species {LnM}(C≡CC≡CLi) which is subsequently treated with the
metal halide to afford the desired diyndiyl complex (Scheme 64).
C C C C {M'L'n'}{LnM}
C C C C H{LnM}
{M'L'n'}Cl
Lithium BaseC C C C{LnM} Li
Scheme 64: The lithiation of a diynyl complex to synthesise diyndiyl complexes This method was first reported in 1990 by Wong,27 followed by Gladysz and co-
workers in 1992. They applied the method to Re(C≡CH)(PPh3)(NO)Cp* and
Re(C≡CH)(PPh3)(NO)Cp for the synthesis of a range of complexes.138,139 For
example, trans-{Cp*(PPh3)(NO)Re}(C≡C){Rh(PPh3)2(CO)} was synthesised from
the treatment of Re(C≡CH)(PPh3)(NO)Cp* with n-BuLi and the subsequent reaction
of the generated lithiated complex Re(C≡CLi)(PPh3)(NO)Cp* with trans-
RhCl(CO)(PPh3)2 (Scheme 65).
C C HRe
ON PPh3-78oC
n-BuLiC C LiRe
ON PPh3
C C {MLn}Re
ON PPh3 C C PdRe
ON PPh3
C C RhRe
ON PPh3
{MLn}Cl
{MLn} = TMS SnPh3
PdCl2(PEt3)2
PEt3
PEt3
Cl
RhCl(PPh3)2(CO)
PPh3
PPh3
CO
Scheme 65: The deprotonation and metalation of the complex Re(C≡CH)(PPh3)(NO)Cp*
108
A few years later, the same group extended their work to the lithiation of the diynyl
complex Re(C≡CC≡CH)(PPh3)(NO)Cp*.22 The lithiated complex
Re(C≡CC≡CLi)(PPh3)(NO)Cp* was generated and then reacted with trans-
PdCl2(PEt3)2 to afford {Cp*(PPh3)(NO)Re}(C≡CC≡C){PdCl(PEt3)2)} or with trans-
RhCl(CO)(PPh3)2 to give {Cp*(PPh3)(NO)Re}(C≡CC≡C){Rh(PPh3)2(CO)} (Scheme
66)
C CRe
ON PPh3-80oC
n-BuLi
PdCl2(PEt3)2 RhCl(PPh3)2(CO)
C C H C CRe
ON PPh3
C C Li
C CRe
ON PPh3
C C Pd
PEt3
PEt3
Cl C CRe
ON PPh3
C C Rh
PPh3
PPh3
CO
Scheme 66: The deprotonation and metalation of Re(C≡CC≡CH)(PPh3)(NO)Cp*
Furthermore, our group applied the lithiation method to the synthesis of two tungsten
complexes. First, it was reported that W(C≡CC≡CH)(CO)3Cp was lithiated with LDA
at -78oC and quenched by TMSCl to afford W(C≡CC≡CTMS)(CO)3Cp.20 Secondly,
the reaction of W(C≡CC≡CLi)(CO)3Cp with MnI(CO)5 gave the complex
{W(CO)3Cp}(C≡CC≡C){Mn(CO)5} (Scheme 67).31
C CW
OC -78oC
LDAC C H C C C C Li
CO CO
W
OC CO CO
C C C C TMSW
OC CO CO
C C C C Mn(CO)5W
OC CO CO
MnI(CO)5TMSCl
Scheme 67: The deprotonation and metalation of the complex W(C≡CC≡CH)(CO)3Cp
109
This method was also employed with the iron complex Fe(C≡CC≡CH)(CO)2Cp*
which was treated with s-BuLi, followed by FeCl(CO)2Cp* to give the complex
{Fe(CO)2Cp*}2(C≡CC≡C).26 Similarly, the lithiation of Ru(C≡CH)(PPh3)2Cp* was
achieved using n-BuLi or t-BuLi in a THF/hexane mixture.140 The lithium
intermediate Ru(C≡CLi)(PPh3)2Cp* then reacted with {MLn}Cl ({MLn} = TMS,
GeMe3 and SnBu3n) to give {Cp*(PPh3)2Ru}(C≡C){MLn} (Scheme 68).
Cp*(PPh3)2Ru C C H Cp*(PPh3)2Ru C C Li
Cp*(PPh3)2Ru C C {MLn}
n-BuLi
-70oC
{MLn}Cl
{MLn} = TMS, GeMe3, SnBu3n
Scheme 68: The deprotonation and metalation of the complex Ru(C≡CH)(PPh3)2Cp*
110
3.2. Aim of this work
The primary aim of this work was to develop a new methodology that would allow
the synthesis of novel diynyl and diyndiyl complexes. The synthetic route is based on
the method first described by Wong which involves the lithiation of a diynyl complex,
followed by its metallation with a metal halide.
This chapter reports the lithiation of two ruthenium(II) diynyl complexes
Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp and the synthesis of the
lithium complexes Ru(C≡CC≡CLi)(dppe)Cp* and Ru(C≡CC≡CLi)(PPh3)2Cp. The
most favorable conditions for their formation are studied by using assay reactions.
Furthermore, the synthesis and characterisation of new asymmetric diyndiyl
complexes of general formula [Ru](C≡CC≡C){MLn} has been achieved by applying
the new synthetic method.
111
3.3. Results and Discussion
3.3.1. The lithiation of [Ru](C≡CC≡CH) ([Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp)
3.3.1.1. Synthetic strategy
In the Introduction, it was shown that one method for the synthesis of asymmetric
complexes is the lithiation of terminal diynyl ligands with strong organolithium bases
(BuLi, LDA) followed by treatment with a metal halide. According to these studies, it
was anticipated that the diynyl complexes [Ru](C≡CC≡CH) (where [Ru] =
Ru(dppe)Cp*, Ru(PPh3)2Cp) could be lithiated using organolithium bases. Hence,
these complexes were treated with a strong organolithium base (BuLi, LDA, MeLi) in
THF at -78oC and the initial bright yellow solution rapidly changed to a darker
yellow. The solution was then assumed to contain the [Ru](C≡CC≡CLi) species.
Furthermore, it was shown in previous work that nucleophiles similar to
[Ru](C≡CC≡CLi) can be used as reactive intermediates in further syntheses; they
react readily with electrophiles such as transition-metal chlorides. Hence, in order to
assay the [Ru](C≡CC≡CLi) species generated in situ, a two-step reaction was
proposed. The first step is the deprotonation of [Ru](C≡CC≡CH) as described above
and the second step involves the addition of a metal halide (Scheme 69). It is
noteworthy that this is providing a new convenient method for the synthesis of new
diynyl and diyndiyl ruthenium(II) complexes.
C C C C {MLn}[Ru]
C C[Ru] C C H
{MLn}Cl
CC C C[Ru] LiLithium Base
THF in situ-78oC
[Ru] = Ru(dppe)Cp* Ru(PPh3)2Cp
Scheme 69: A two-step reaction for the formation of [Ru](C≡CC≡C){MLn} complexes
112
3.3.1.2. NMR study
Spectroscopic monitoring was attempted on the lithiation reaction of
Ru(C≡CC≡CH)(dppe)Cp*. The 1H and 31P NMR spectra of the lithium complex
Ru(C≡CC≡CLi)(dppe)Cp* were obtained by dissolving Ru(C≡CC≡CH)(dppe)Cp* in
THF-d8 in an NMR tube and then adding n-BuLi at -78oC.
The 31P NMR spectrum of the Ru(C≡CC≡CLi)(dppe)Cp* species shows a single peak
at δ 82.9. The chemical shift for the Ru(C≡CC≡CH)(dppe)Cp* in THF-d8 at -78oC
was at δ 80.7. So, the difference between the neutral and the deprotonated species is a
downfield shift of 2.2 ppm. The 1H NMR spectrum of Ru(C≡CC≡CH)(dppe)Cp* in
THF-d8 at -78oC shows five resonances: one at δ 7.78-7.25 for the phenyl groups, two
multiplets at δ 2.75-2.73 and 2.17-2.15 for the dppe ligand, one singlet at δ 1.59 for
the methyl groups of the Cp* ligand. The most significant resonance in this study is
the presence of the terminal proton as a singlet at δ 1.34. In comparison, the 1H NMR
spectrum of the Ru(C≡CC≡CLi)(dppe)Cp* species also showed a multiplet for the
phenyl groups at δ 7.76-7.23, two multiplets at δ 2.76-2.71 and 2.16-1.93 for the dppe
ligand and one singlet at δ 1.53 for the methyl groups of the Cp* ligand. These values
are very close to those for Ru(C≡CC≡CH)(dppe)Cp*. The most interesting feature is
the shift of the terminal proton to δ 1.68 and the decrease in its relative ratio
compared to the Cp* singlet. The ratio decreased from approximately half of its
original value. More spectra were taken at later time interval but did not show any
major change. When an excess of n-BuLi was added, the studied region become very
broad and no further analysis could be completed.
In conclusion, the efficiency of the synthesis of the Ru(C≡CC≡CLi)(dppe)Cp* species
could not be determined from these spectroscopic studies. The small chemical shift
differences in the 31P and the 1H NMR spectra are not conclusive. There is a decrease
in the intensity of the terminal proton, but it appears that complete metallation has not
occurred. Therefore, the formation of the Ru(C≡CC≡CLi)(dppe)Cp* complex was
further studied by using assay reactions.
113
3.3.2. Investigation of the formation of [Ru](C≡CC≡CLi)
In this Section, the conditions that are the most favorable for the lithiation of the
complexes [Ru](C≡CC≡CH) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) are
described. In order to explore this, the syntheses of known complexes
[Ru](C≡CC≡CTMS) (where [Ru] = Ru(dppe)Cp* (22), Ru(PPh3)2Cp (23)) and
[Ru](C≡CC≡C[Au(PPh3)]} (where [Ru] = Ru(dppe)Cp* (24), Ru(PPh3)2Cp (25))
were attempted.
3.3.2.1. Synthesis of [Ru](C≡CC≡CTMS)
The syntheses of [Ru](C≡CC≡CTMS) (where [Ru] = Ru(dppe)Cp* (22),
Ru(PPh3)2Cp (23)) are usually achieved by the reaction of the chlororuthenium
complexes [Ru]Cl with an excess of H-C≡CC≡C-TMS in the presence of Na[BPh4]
in a THF/NEt3 solvent mixture (Scheme 70).30
Cl + C C C C TMSC C TMSHNa[BPh4]
THF/NEt350oC
[Ru][Ru]
[Ru] = Ru(dppe)Cp* (79%) (22) Ru(PPh3)2Cp (94%) (23)
2
Scheme 70: Synthesis of 22 and 23
The new approach for the syntheses of 22 and 23 is based on the lithiation of the
diynyl complexes [Ru](C≡CC≡CH) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) with
an organolithium base followed by treatment with the metal halide TMSCl (Scheme
71).
114
C C C C TMS[Ru]
C C[Ru] C C H
TMSCl
CC C C[Ru]Lithium Base
in situ
[Ru] = Ru(dppe)Cp* (22), Ru(PPh3)2Cp (23)
Li
Scheme 71: A new method for the synthesis of 22 and 23 The lithiation of [Ru](C≡CC≡CH) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) with a
range of organolithium bases, different solvents, temperatures and reaction times was
tried in order to find the best conditions for the synthesis of [Ru](C≡CC≡CLi) (where
[Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp). The terminal lithium complexes were generated
in situ and subsequent addition of TMSCl allowed the formation of the diynyl
complexes 22 and 23. Some representative experiments are summarised in Table 10.
The best yield 86% of Ru(C≡CC≡CTMS)(dppe)Cp* (22) and 80% of
Ru(C≡CC≡CTMS)(PPh3)2Cp (23) were achieved using two equivalents of n-BuLi, in
THF at -78 oC for 30 min, followed by addition of TMSCl and warming the solution
to room temperature.
Complexes 22 and 23 were characterised by 1H and 31P NMR spectroscopy and the
data were consistent with the literature values.12,59 The 1H NMR spectrum of 22
shows a singlet at δ 0.29 confirming the presence of the trimethylsilyl group, a singlet
at δ 1.56 corresponding to the Cp* ligand, multiplets at δ 2.56-2.52 and 1.88-1.81
corresponding to the hydrogens of the -CH2CH2- group in dppe and a broad multiplet
at δ 7.87-7.02 for the phenyl groups. The 31P NMR spectrum of 22 shows one singlet
at δ 81.3 assigned to the phosphorus nuclei bound to the ruthenium. In the 1H NMR
spectrum of complex 23, a multiplet at δ 7.59-6.91 for the phenyl groups, a singlet at
δ 4.36 which corresponds to the cyclopentadienyl Cp ligand and a singlet at δ 0.28 for
the TMS group are present. In the 31P NMR spectrum, one resonance at δ 50.8 was
assigned to the phosphorus atoms coordinated to the ruthenium.
115
Reagents Solvent Temp. (oC) Reaction Time Yield (%)
Ru(C≡CC≡CH)(dppe)Cp*
n-BuLi (1 eq)
TMSCl
THF -78 1 h (-78oC), then
to r.t.
78
Ru(C≡CC≡CH)(dppe)Cp*
n-BuLi (2 eq)
TMSCl
THF -78 30 min (-78oC),
then to r.t.
86
Ru(C≡CC≡CH)(PPh3)2Cp
n-BuLi (1 eq)
TMSCl
1 : 1
THF/hexane
-40 1 h (-40oC), then
to r.t.
74
Ru(C≡CC≡CH)(PPh3)2Cp
n-BuLi (2 eq)
TMSCl
THF -78 30 min (-78oC),
then to r.t.
80
Ru(C≡CC≡CH)(dppe)Cp*
t-BuLi (1 eq)
TMSCl
1 : 1
THF/Et2O
-80 1 h (-80oC), then
to r.t.
75
Ru(C≡CC≡CH)(PPh3)2Cp
MeLi (1 eq)
TMSCl
2 : 1
THF/hexane
-20 1 h (-20oC), then
to r.t.
74
Ru(C≡CC≡CH)(dppe)Cp*
MeLi (2 eq)
TMSCl
1 : 1
THF/hexane
0 30 min (0oC), then
to r.t.
70
Ru(C≡CC≡CH)(dppe)Cp*
n-BuLi (1 eq) + TMEDA
TMSCl
2 : 1
THF/hexane
-80 2 h (-80oC), then
to r.t.
64
Ru(C≡CC≡CH)(PPh3)2Cp
LDA (1 eq)
TMSCl
THF -78 2 h (-78oC), then
to r.t.
59
Table 9: Summary of experiments for the synthesis of 22 and 23
116
3.3.2.2. Synthesis of [Ru]{C≡CC≡C[Au(PPh3)]}
The synthesis of two known complexes [Ru](C≡CC≡C[Au(PPh3)]} [where [Ru] =
Ru(dppe)Cp* (24), Ru(PPh3)2Cp (25)] was attempted in order to assay further the
synthesis of Ru(C≡CC≡CLi)(PPh3)2Cp.
It was reported previously that the reaction of [Ru](C≡CC≡CH) (where [Ru] =
Ru(dppe)Cp*, Ru(PPh3)2Cp) with the chlorogold precursor AuCl(PPh3) in the
presence of K[N(TMS)2] afforded the complexes Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp*
(24) and Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp (25) (Scheme 72).30
C C[Ru] C C C[Ru] C Au(PPh3)THF
AuCl(PPh3)THF
AuCl(PPh3)K[N(TMS)2]
C C H[Ru] +
[Ru] = Ru(dppe)Cp* (69%) (24) Ru(PPh3)2Cp (93%) (25)
2
Scheme 72: Synthesis of 24 and 25
The new synthetic method was applied in order to synthesise complexes 24 and 25
(Scheme 73) but also to find what conditions are most favorable for the synthesis of
[Ru](C≡CC≡CLi) (Table 11). It was found that the treatment of [Ru](C≡CC≡CH)
with two equivalents of n-BuLi at -78oC followed by addition of one equivalent of
AuCl(PPh3) gives the best yields, 85% for Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp* (24)
and 70% for Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp (25).
C C C C Au(PPh3)[Ru]
C C[Ru] C C H
AuCl(PPh3)
CC C C[Ru]Lithium Base
in situ
[Ru] = Ru(dppe)Cp* (24), Ru(PPh3)2Cp (25)
Li
Scheme 73: A new method for the synthesis of 24 and 25
117
Reagents Solvent Temp. (oC) Reaction Time Yield (%)
Ru(C≡CC≡CH)(dppe)Cp*
n-BuLi (1 eq)
AuCl(PPh3)
THF -78 30 min (-78oC),
then to r.t.
60
Ru(C≡CC≡CH)(dppe)Cp*
n-BuLi (2 eq)
AuCl(PPh3)
THF -78 30 min (-78oC),
then to r.t.
85
Ru(C≡CC≡CH)(PPh3)2Cp
n-BuLi (1 eq)
AuCl(PPh3)
1 : 1
THF/hexane
-80 1 h (-80oC), then
to r.t.
65
Ru(C≡CC≡CH)(PPh3)2Cp
n-BuLi (2 eq)
AuCl(PPh3)
THF -78 30 min (-78oC),
then to r.t.
70
Ru(C≡CC≡CH)(dppe)Cp*
LDA (1 eq)
AuCl(PPh3)
1 : 1
THF/hexane
-78 1 h (-78oC), then
to r.t.
62
Ru(C≡CC≡CH)(PPh3)2Cp
MeLi (1 eq)
AuCl(PPh3)
1 : 1
THF/Et2O
-20 1 h (-20oC), then
to r.t.
56
Ru(C≡CC≡CH)(dppe)Cp*
MeLi (2 eq)
AuCl(PPh3)
2 : 1
THF/hexane
-20 30 min (-20oC),
then to r.t.
64
Table 10: Summary of experiments for the synthesis of 24 and 25
Complexes 24 and 25 were readily identified from their spectroscopic data, which are
consistent with the literature values.12,141 Both 1H NMR spectra show a multiplet
assigned to the phenyl groups and the characteristic peaks for the Ru(dppe)Cp* and
the Ru(PPh3)2Cp ligands. In the 31P NMR spectra of 24 and 25, two singlets were
present in a 2:1 ratio corresponding to the phosphorus nuclei bound to the ruthenium
and the phosphorus nucleus coordinated to the gold.
118
In conclusion, the best conditions for the lithiation of diynyl complexes
[Ru](C≡CC≡CH) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) involve the addition of
two equivalents of n-BuLi at –78oC, followed by the addition of a metal halide. The
percentage yield for the test reactions with TMSCl and AuCl(PPh3) are very high.
This indicates that the [Ru](C≡CC≡CLi) species is successfully formed and reacted
efficiently with metal halides. It is also noteworthy that complexes 22 and 24 were
obtained in better yields than from the previous reported methods (86% and 85%
yield versus 79% and 69% yield, respectively).30 Furthermore, the availability of these
two nucleophilic complexes [Ru](C≡CC≡CLi) (where [Ru] = Ru(dppe)Cp*,
Ru(PPh3)2Cp) offers a new synthetic route for the synthesis of a range of diynyl and
diyndiyl complexes.
3.3.3. Reactions of [Ru](C≡CC≡CLi) with various metal halides
3.3.3.1. Reaction with (AuCl)2(µ-dppm)
In 1993, the synthesis of the gold(I) alkynyl complex Au2(µ-dppe)(C≡CPh)2 was
reported.142 This compound was found to emit luminescence (Figure 45).
P
P
PhPh
Ph Ph
Au C C
Au C C
Figure 45: Representation of Au2(µ-dppe)(C≡CPh)2
Several gold(I) complexes have been used as precursors for alkynylgold(I)
derivatives. These include AuCl(L) (L = PPh3, SC4H8),108,109 [ppn][Au(acac)2]111 and
(AuCl)2(µ-dppm)110. In 2002, our research group reported the reactions of various
gold(I) complexes. For example, the diynyl complex {Au(C≡CC≡CH)}2(µ-dppm) was
119
synthesised from the reaction of (AuCl)2(µ-dppm) and HC≡CC≡CH under Cadiot-
Chodkiewicz conditions. Similarly, the complex {Au(C≡CC≡C[W(CO3)Cp])}2(µ-
dppm) was obtained from W(C≡CC≡CH)(CO3)Cp and (AuCl)2(µ-dppm) (Scheme
74).65
R C C C C H
R C C C C Au
R C C C C Au
PPh2
PPh2
CuI NHEt2
+ (AuCl)2(µ-dppm)
R = H or W(CO)3Cp
Scheme 74: Two examples of gold(I) complexes
Following these two examples, it was suggested that a new complex containing two
{Ru(dppe)Cp*}C≡CC≡C moieties linked by the gold(I) fragment Au2(µ-dppm) could
be synthesised. It was found that this compound could not be obtained under Cadiot-
Chodkiewicz conditions. Hence, the new synthetic method involving the lithiation of
Ru(C≡CC≡CH)(dppe)Cp* was proposed as an alternative route.
Two equivalents of Ru(C≡CC≡CH)(dppe)Cp* dissolved in THF were treated with n-
BuLi at -78oC. The gold(I) compound (AuCl)2(µ-dppm) was then added to the
Ru(C≡CC≡CLi)(dppe)Cp* species generated in situ. After warming-up the mixture to
room temperature and work-up the complex {Au(C≡CC≡C[Ru(dppe)Cp*])}2(µ-
dppm) (26) was obtained in 90% yield (Scheme 75).
120
Cp*(dppe)Ru C C C C Au
Cp*(dppe)Ru C C C C Au
PPh2
PPh2
C C C C Lin-BuLi
THF
(AuCl)2(µ-dppm)
Cp*(dppe)Ru C C C C Au
Cp*(dppe)Ru C C C C Au
PPh2
PPh2
n-BuLi
(26)
Cp*(dppe)RuC C C C HCp*(dppe)Ru
Scheme 75: Synthesis of 26
Complex 26 was fully characterised by 1H, 31P and 13C NMR, IR, ES-MS and
microanalysis (Table 14). In the 1H and 13C NMR spectra, the characteristic peaks for
the Ru(dppe)Cp* and dppm ligands are present. The carbons of the carbon chains
were not observed in the 13C NMR spectrum due to the lack of solubility of complex
26 in solvents suitable for NMR spectroscopy. However, two ν(C≡C) bands at 2106
and 1982 cm-1 were observed in the infrared spectrum. The 31P NMR spectrum of 26
shows two resonances at δ 82.0 and 35.6 in a 2:1 ratio which were assigned to the
phosphorus atoms on the ruthenium and the gold, respectively. Further
characterisation of 26 was obtained from the ES-MS which contains a fragment ion
corresponding to [M - H]+ at m/z 2143.
Crystals suitable for an X-ray study have not yet been obtained to confirm the exact
conformation of 26. Previously, it was found that the complex {Au(C≡CtBu)}2(µ-
dppm) has a U-shaped geometry, with an intramolecular Au…Au contact of 3.331(1)
Å, each Au(I) centre being approximately linearly coordinated by the phosphorus
atom and the alkynyl group.143 Furthermore, in the case of
{Au(C≡CC≡C[W(CO3)Cp])}2(µ-dppm), it was speculated that the increased steric
bulk of the W(CO)3Cp moieties is likely to result in breaking of the intramolecular
Au…Au contact, with twisting of the Au-phosphine backbone.65 It is likely that
complex 26 will show a very similar structure to that of
{Au(C≡CC≡C[W(CO3)Cp])}2(µ-dppm) since the Ru(dppe)Cp* moieties are also
bulky.
121
3.3.3.2. Reaction with cis-PtCl2(PPh3)2
The reaction of Ru(C≡CC≡CH)(dppe)Cp* with n-BuLi at -78oC afforded the
nucleophilic species Ru(C≡CC≡CLi)(dppe)Cp* which was reacted in situ with one
equivalent of cis-PtCl2(PPh3)2. Complex trans-Ru{C≡CC≡C[PtCl(PPh3)2]}(dppe)Cp*
(27) was isolated from this reaction in 40% yield (Scheme 76).
C C C CRu
Ph2P PPh2
H
n-BuLi /THF
C C C CRu
Ph2P PPh2
Pt-78oC
PtCl2(PPh3)2
PPh3
Ph3P
ClC C CRu
Ph2P PPh2
H C C C CRu
Ph2P PPh2
Pt-78oC
PPh3
Ph3P
Cl
(27)
Scheme 76: Synthesis of 27
Complex 27 was identified from its spectroscopic data (Table 13). The characteristic
peaks for the Ru(dppe)Cp* group are present in the 1H and 31P NMR spectra. The 1H
NMR spectrum also shows a broad multiplet at δ 8.02-6.83 due to the phenyl groups
while in the 31P NMR spectrum a resonance was observed at δ 22.2 for the
phosphorus atoms of the PPh3 groups. Further characterisation of 27 was obtained
from the ES-MS which contained a peak corresponding to [M]+ at m/z 1437 and
fragmentation ions [M - H]+ at m/z 1436 and [Ru(dppe)Cp*]+ at m/z 635.
3.3.3.3. Reactions with GeClPh3 and SnClPh3
In Section 3.3.2.1, it was described that Ru(C≡CC≡CLi)(dppe)Cp* reacts with the
silyl halide TMSCl. Following these results, the reaction of
Ru(C≡CC≡CLi)(dppe)Cp* with tin and germanium halides, two other group 14
metalloids, was suggested in order to synthesise complexes that have not been made
by already established methods.
122
The first step of the reaction involved the generation in situ of
Ru(C≡CC≡CLi)(dppe)Cp* which was obtained from the lithiation of
Ru(C≡CC≡CH)(dppe)Cp* with n-BuLi at -78oC. This was then followed by the
addition of one equivalent of either GeClPh3 or SnClPh3.
Ru(C≡CC≡CGePh3)(dppe)Cp* (28) and Ru(C≡CC≡CSnPh3)(dppe)Cp* (29) were
obtained in 82% and 70% yield as a yellow crystalline solids, respectively (Scheme
77).
C C C CRu
Ph2P PPh2
Hn-BuLi
THFC C C CRu
Ph2P PPh2
Li
{MLn}Cl
C C C CRu
Ph2P PPh2
{MLn}
-78oC
{MLn} = GePh3 (28) SnPh3 (29)
Scheme 77: Synthesis of complex 28 and 29
Complexes 28 and 29 were identified from their spectroscopic data and elemental
analysis. All the data are summarised in Table 14. In the 1H, 31P and 13C NMR
spectra, the characteristic peaks for the Ru(dppe)Cp* ligand are present. The 13C
NMR spectra of 28 and 29 also contain the resonances for the carbon atoms of the C4
chain. The ES-MS of complex 28 contains a [M + Na]+ peak at m/z 1009, while the
spectrum for complex 29 has a [M]+ peak at m/z 1033.
Single crystals suitable for X-ray studies of complex 28 were grown from
THF/hexane. Figure 46 shows the ORTEP plot of 28, while selected structural data
are collected in Table 12. The Ru-C(1) bond length is equal to 1.975(3) Å. This value
is close to the one found for complex Ru(C≡CC≡CTMS)(dppe)Cp* (22) [1.983(2)
Å].1 The C(1)-C(2) bond length is equal to 1.224(3) Å, the C(2)-C(3) distance is
1.377(3) Å and the C(3)-C(4) distance is 1.209(3) Å. The expected alternating short
123
C(1)-C(2), long C(2)-C(3) and short C(3)-C(4) bonds are consistent with the diynyl
nature of the bonds. The C(4)-Ge distance is equal to 1.881(3) Å, which is a slighlty
longer bond than the C(4)-Si bond [1.822(2) Å]30 in complex 22 reflecting the
different atomic radii (Si = 1.17, Ge = 1.22 Å). The angles Ru-C(1)-C(2) [176.5(2) o],
C(1)-C(2)-C(3) [176.2(3) o] and C(2)-C(3)-C(4) [179.0(3) o] and C(3)-C(4)-Ge
[165.5(2) o] in 28 are close to linear.
Figure 46: ORTEP view of 28
Bond distances (Å) Bond Angles (o)
Ru-C(1) 1.975(3) Ru-C(1)-C(2) 176.5(2)
Ru-P(1) 2.278(7) P(1)-Ru-P(2) 82.7(2)
Ru-P(2) 2.273(7) P(1)-Ru-C(1) 79.2(7)
Ru-C(Cp*) 2.241(2) - 2.286(2) P(2)-Ru-C(1) 89.0(7)
Ru-C(Cp*) (av.) 2.258(2) C(1)-C(2)-C(3) 176.2(3)
C(1)-C(2) 1.224(3) C(2)-C(3)-C(4) 179.0(3)
C(2)-C(3) 1.377(3) C(3)-C(4)-Ge 165.5(2)
C(3)-C(4) 1.209(3)
C(4)-Ge 1.881(3)
Table 11: Selected bond distances (Å) and angles (o) for 28
124
Electrochemical studies of complexes 28 and 29 were also completed. The cyclic
voltammograms of complexes 28 and 29 show a single fully-reversible process at
+0.41 V and +0.40 V, respectively. These redox processes are diffusion controlled. It
must be noted that in the case of complex 22, a single irreversible process was
observed at ca +0.43 V.30 Hence, the comparison of the electrochemical properties of
the three analogous complexes 22, 28 and 29 shows that these complexes have very
similar oxidation potentials.
3.3.3.4. Reaction with [CuCl(PPh3)]4
The metal halide [CuCl(PPh3)]4 is readily available,144 so following the work done
with the AuCl(PPh3) metal halide (Section 3.3.2.2.), a similar reaction between
Ru(C≡CC≡CH)(dppe)Cp* and [CuCl(PPh3)]4 was proposed. The first step of the
reaction involved the generation in situ of Ru(C≡CC≡CLi)(dppe)Cp* as previously
described, followed by addition of the metal halide [CuCl(PPh3)]4. This reaction
should afford the complex Ru(C≡CC≡C[Cu(PPh3)])(dppe)Cp*. However, the
expected product was not obtained. Instead, a complex containing two Ru(dppe)Cp*
units linked by a C8 carbon chain {Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*}
(30) was formed in 85% yield (Scheme 78).
C C C C HRu
Ph2P PPh2
C C C C LiRu
Ph2P PPh2
n-BuLi
THF
[CuCl(PPh3)]4
C C CRu
Ph2P PPh2
C C C C Cu(PPh3)Ru
Ph2P PPh2
C C C C C Ru
PPh2Ph2P
[CuCl(PPh3)]4
C C C C HRu
Ph2P PPh2
C C C C LiRu
Ph2P PPh2
n-BuLi
THF
[CuCl(PPh3)]4
C C CRu
Ph2P PPh2
C C C CRu
Ph2P PPh2
C C C C C Ru
PPh2Ph2P
[CuCl(PPh3)]4
(30)
Scheme 78: The reaction of Ru(C≡CC≡CH)(dppe)Cp* with [CuCl(PPh3)]4
125
A possible explanation can be suggested for the formation of complex 30. According
to previous studies, it was found that under Hay coupling conditions (CuCl/tmeda/O2
or air) an oxidative coupling of 1-alkynes containing MLn groups, {MLn}(C≡C)mH,
doubles the chain length to give {MLn}2(µ-C≡C)2m. For example, oxidative coupling
of M(C≡CC≡CH)(CO3)Cp (M = Mo, W) gives {M(CO3)Cp}2{µ-(C≡C)4}(Scheme
79).3
C C C C H{LnM} C C C CC C C C {MLn}{LnM}[Cu(tmeda)]+
O2
{MLn} = Mo(CO)3Cp; W(CO)3Cp
Scheme 79: Oxidative coupling of {MLn}(C≡C)mH
In our reaction, [CuCl(PPh3)]4 might have acted as a catalyst allowing the oxidative-
coupling of the {Cp*(dppe)Ru}-C≡CC≡C- unit via spontaneous C-C bond formation
giving the complex {Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*} (30).
Complex 30 had been previously synthesised from the reaction of the chloro-
ruthenium complex Ru(dppe)Cp*Cl with half an equivalent of TMS-(C≡C)4-TMS in
the presence of KF (Scheme 80).12
Ru
Ph2P PPh2
Cl TMS C C TMS4
KF
MeOHC C CRu
Ph2P PPh2
C C C C C Ru
PPh2Ph2P
Ru
Ph2P PPh2
Cl + TMS C C TMS4
KF
MeOHC C CRu
Ph2P PPh2
C C C C C Ru
PPh2Ph2P(30)
Scheme 80: Previously reported method for the synthesis of 30
Complex 30 was characterised by 1H and 31P NMR spectroscopy, IR and ES-MS and
the data collected are consistent with the literature values (Table 14).12 The
Ru(dppe)Cp* ligands were characterised by typical peaks in the 1H and 31P NMR
spectra. In the IR spectrum, two ν(C≡C) bands at 2101 and 1949 cm-1 were observed
and in the ES-MS [M]+ at m/z 1366 and [Ru(dppe)Cp*]+ at m/z 635 were present.
126
Although complex 30 was synthesised previously, no crystals suitable for X-ray
diffraction were obtained. However in this work, single crystals suitable for X-ray
studies were grown from CH2Cl2/hexane. Figure 47 shows the ORTEP plot of
complex 30 and selected bond distances and angles are given in Table 13. The Ru-
C(1) bond length of 2.006(3) Å is close to the value expected for a ruthenium carbon
single bond (2.01 Å). The C(1)-C(2) bond length is equal to 1.230(4) Å, the C(3)-C(4)
distance of 1.226(5) Å, the C(2)-C(3) distance is 1.370(4) Å, and are therefore
consistent with being C≡C triple and C-C single bonds, respectively. The angles Ru-
C(1)-C(2) [177.6(2) o], C(1)-C(2)-C(3) [177.0(3) o] and C(2)-C(3)-C(4) [177.6(3) o] in
30 are nearly linear.
Figure 47: ORTEP view of 30
Bond distances (Å) Bond Angles (o)
Ru(1)-C(1) 2.006(3) Ru-C(1)-C(2) 177.6(2)
Ru(1)-P(1) 2.258(6) P(1)-Ru-P(2) 83.3(2)
Ru(1)-P(2) 2.275(5) P(1)-Ru-C(1) 84.0(7)
Ru-C(Cp*) 2.223(1) - 2.267(3) P(2)-Ru-C(1) 84.9(6)
Ru-C(Cp*) (av.) 2.252(3) C(1)-C(2)-C(3) 177.0(3)
C(1)-C(2) 1.230(4) C(2)-C(3)-C(4) 177.6(3)
C(2)-C(3) 1.370(4)
C(3)-C(4) 1.226(5)
Table 12: Selected bond distances (Å) and angles (o) for 30
127
Subsequently, Ru(C≡CC≡CH)(PPh3)2Cp was treated with n-BuLi at -78oC and
[CuCl(PPh3)]4 was added to the lithio intermediate Ru(C≡CC≡CLi)(PPh3)2Cp. After
removal of the solvent and column chromatography, the yellow product
{Cp(Ph3P)2Ru}(C≡CC≡C){Cu(PPh3)} (31) was obtained in 40% yield (Scheme 81).
-78oCCu(PPh3)C C C CRu
Ph3P PPh3
HC C C CRu
Ph3P PPh3[CuCl(PPh3)]4
n-BuLi
C C C CRu
Ph3P PPh3
HC C C CRu
Ph3P PPh3[CuCl(PPh3)]4 (31)
THF
Scheme 81: Synthesis of 31
Complex 31 was characterised by elemental analysis, IR, 1H and 31P NMR and ES-
MS (Table 15). The 1H and 31P NMR spectra of 31 confirm the presence of the
Ru(PPh3)2Cp ligand. In the 31P NMR, one singlet is also present at δ 38.5 for the
phosphorus associated with the copper moiety. The ES-MS shows one [M + MeOH]+
at m/z 1096, one fragment for [Ru(PPh3)2Cp]+ at m/z 691 and one fragment at m/z 429
for the [Ru(PPh3)Cp]+ moiety.
In comparison to the reaction of Ru(C≡CC≡CH)(dppe)Cp* and [CuCl(PPh3)]4, this
reaction gave the expected product and there was no indication of the presence of an
oxidative coupling product. The difference between the two reactions is the two
different ruthenium metal-ligand moiety (Ru(PPh3)2Cp vs Ru(dppe)Cp*). Hence, it
can be assumed that the more electron donating ruthenium ligand Ru(dppe)Cp* has an
influence on the synthesis of complex 30.
128
3.3.3.5. Reaction with RhCl(CO)(PPh3)2
Similarly, the complex {Cp(Ph3P)2Ru}(C≡CC≡C){Rh(CO)(PPh3)2} (32) was
obtained from the reaction of Ru(C≡CC≡CH)(PPh3)2Cp treated with n-BuLi at -78oC,
followed by adddition of one equivalent of RhCl(CO)(PPh3)2 (Scheme 82).
n-BuLi-78oC
RhCl(CO)(PPh3)2
Rh(CO)(PPh3)2C C C CRu
Ph3P PPh3
HC C C CRu
Ph3P PPh3(32)
THF
Scheme 82: Synthesis of 32
Complex 32 displayed the expected resonances in the 1H, 31P NMR, IR, microanalysis
and ES-MS (Table 15). In the 1H and 31P NMR spectra, the characteristic peaks for the
Ru(PPh3)2Cp ligand are present. The phosphorus atoms on the Rh(CO)(PPh3)2 ligand
are observed at δ 38.5 in the 31P NMR spectrum. In the infrared spectrum, two
ν(C≡C) bands at 1978 and 1955 cm-1 and one ν(CO) band at 2108 cm-1 were
observed. The ES-MS of 32 shows a peak for the molecular ion at m/z 1394 and
fragmentation ions corresponding to [Ru(PPh3)2Cp]+at m/z 691 and [Ru(PPh3)Cp]+at
m/z 429.
129
Table 13: Spectroscopic data for complexes 26 - 30
Complex IR (cm-1) ν(C≡C)
1H NMR (δ)
13C NMR (δ)
31P NMR (δ)
ES-MS (m/z)
26 2106 (m) 1982 (m)
7.95-6.85 (m, 60H, Ph); 3.23 (s, 2H, CH2); 2.89-2.80, 1.92-1.81 (2 x m, 8H, CH2CH2); 1.56 (s, 15H, Cp*)
133.76-127.64 (m, Ph); 93.12 (s, C5Me5); 43.33 (s, CH2); 30.12-29.86 (m, CH2CH2); 10.08 (s, C5Me5)
82.0 (s, dppe) 35.6 (s, dppm)
2143, [M - H]+; 1366, [M - Au2(dppm)]+; 675, [Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+.
27 2105 (m) 1984 (m)
8.02-6.83 (m, 50H, Ph); 2.39-2.20, 1.90-1.84 (2 x m, 2 x 2H, CH2CH2); 1.54 (s, 15H, Cp*)
81.9 (s, dppe) 22.2 (s, PPh3)
1437, [M+]; 1436, [M - H]+ ; 635, [Ru(dppe)Cp*]+
28 2106 (m) 2000 (m)
7.85-6.89 (m, 35H, Ph); 2.53-2.50, 1.79-1.75 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*)
137.76-127.64 (m, Ph); 99.42, 93.46, 86.85, 62.40 (s, C1, C2, C3, C4); 93.22 (s, br, C5Me5); 30.12-29.62 (m, CH2CH2); 10.17 (s, C5Me5)
81.0 (s, dppe) 1009, [M + Na]+; 988, [M + H]+; 675, [Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+
29 2081 (m) 1977 (m)
7.89-7.01 (m, 35H, Ph); 2.55-2.52, 1.81-1.78 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*
134.02-127.84 (m, Ph); 103.22, 99.05, 86.85, 74.82 (s, C1, C2, C3, C4); 91.87 (s, C5Me5); 30.01-29.86 (m, CH2CH2); 10.21 (s, C5Me5)
81.2 (s, dppe) 1033, [M]+; 675, [Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+
30 2101 (m) 1949 (m)
7.75-7.03 (m, 40H, Ph); 2.55-2.40, 2.00-1.89 (2 x m, 8H, CH2CH2); 1.53 (s, 30H, Cp*)
80.1 (s, dppe) 1366, [M]+; 635, [Ru(dppe)Cp*]+
130
Table 14: Spectroscopic data for complexes 31 and 32
Complex
IR (cm-1)
1H NMR (δ)
31P NMR (δ)
ES-MS (m/z)
31 ν(C≡C) 2106 (m),
1994 (m) 7.76-6.89 (m, 45H, Ph); 4.24 (s, 5H, Cp)
50.8 (s, Ru(PPh3)2) 38.5 (s, Cu(PPh3))
1096, [M + MeOH]+; 691,
[Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+
32 ν(C≡C) 2108 (m), 1978 (m); ν(CO) 1955 (m)
7.17-6.92 (m, 60H, Ph); 4.35 (s, 5H, Cp)
50.6 (s, Ru(PPh3)2) 38.5 (s, Rh(PPh3)2)
1394, [M]+; 691, [Ru(PPh3)2Cp]+; 429,
[Ru(PPh3)Cp]+.
131
3.4. Conclusions
In summary, this work has demonstrated that the diynyl complexes [Ru](C≡CC≡CH)
(where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) can be lithiated using organolithium
bases. Two different assay reactions which involved the addition of TMSCl and
AuCl(PPh3) were studied. It was found that the lithiation of the complexes
[Ru](C≡CC≡CH) is most favorable under the presence of two equivalents of the
lithium base n-BuLi at -78oC. In addition, the generated lithium complexes
[Ru](C≡CC≡CLi) were reacted with metal halides from a range of metal groups (Si,
Au, Ge, Sn, Pt, Cu and Rh) and afforded new asymmetric complexes.
This is the first example of the lithiation of ruthenium(II) diynyl complexes and this
new synthetic route will allow the synthesis of a wide range of novel diynyl and
symmetric or asymmetric ruthenium(II) diyndiyl complexes.
132
3.5. Experimental
General experimental conditions are detailed on page viii. Reagents:
The compounds Ru(C≡CC≡CH)(dppe)Cp*,30 Ru(C≡CC≡CH)(PPh3)2Cp,30
AuCl(PPh3),136 (AuCl)2(µ-dppm),143 CuCl(PPh3),144 RhCl(CO)(PPh3)2,145
PtCl2(PPh3)2146 were all prepared by standard literature methods. n-BuLi, TMSCl,
GeClPh3, SnClPh3 was used as received from Sigma-Aldrich.
Ru(C≡CC≡CTMS)(dppe)Cp* (22)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (5 mL) was
treated with n-BuLi (0.14 mL, 1.045 M solution in THF) and stirred for 30 min at -
78oC. An aliquot of TMSCl (18 µL, 0.14 mmol) was added and the reaction was
allowed to warm to r.t. over 2 h. Solvent was removed to give a yellow residue which
was then dissolved in hexane (70 mL) and the solution was filtered via cannula and
evaporated to dryness to give Ru(C≡CC≡CTMS)(dppe)Cp* (22) as a bright yellow
powder (47 mg, 86%). 1H NMR (C6D6): δ 7.87-7.02 (m, 20H, Ph); 2.56-2.52, 1.88-
1.81 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*); 0.29 (s, 9H, TMS). 31P NMR
(C6D6): δ 81.3 (s, dppe). Literature 1H NMR (C6D6): δ 7.86-6.89 (m, 20H, Ph); 2.49-
1.78 (2 x m, 2 x 2H, CH2CH2); 1.53 (s, 15H, Cp*); 0.23 (s, 9H, TMS). 31P NMR
(C6D6): δ 81.3 (s, dppe).12
Ru(C≡CC≡CTMS)(PPh3)2Cp (23)
Similarly, from Ru(C≡CC≡CH)(PPh3)2Cp (51 mg, 0.07 mmol) and TMSCl (17 µL,
0.14 mmol) was obtained Ru(C≡CC≡CTMS)(PPh3)2Cp (23) as a bright yellow
powder (45 mg, 80%). 1H NMR (CDCl3): δ 7.59-6.91 (m, 30H, Ph); 4.36 (s, 5H, Cp);
0.28 (s, 9H, TMS). 31P NMR (CDCl3): δ 50.8 (s, PPh3). Literature 1H NMR (CDCl3):
133
δ 7.58-6.92 (m, 30H, Ph); 4.30 (s, 5H, Cp); 0.26 (s, 9H, TMS). 31P NMR (CDCl3): δ
50.7 (s, PPh3).59
Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp* (24)
Similarly, Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.07 mmol) was reacted with
AuCl(PPh3) (39 mg, 0.07 mmol) and afforded Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp*
(24) as a bright yellow powder (72 mg, 85%). 1H NMR (C6D6): δ 7.86-6.96 (m, 35H,
Ph); 2.76-2.73, 2.20-2.14 (2 x m, 2 x 2H, CH2CH2); 1.54 (s, 15H, Cp*). 31P NMR
(C6D6): δ 80.6 (s, dppe); 43.1 (s, PPh3). Literature 1H NMR (C6D6): δ 7.76-7.04 (m,
35H, Ph); 2.77-2.15 (2 x m, 2 x 2H, CH2CH2); 1.52 (s, 15H, Cp*). 31P NMR (C6D6): δ
80.8 (s, dppe); 42.5 (s, PPh3).12
Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp (25)
Similarly, from Ru(C≡CC≡CH)(PPh3)2Cp (51 mg, 0.07 mmol) and AuCl(PPh3) (68
mg, 0.14 mmol) was obtained Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp (25) as a bright
yellow powder (57 mg, 70%). IR (Nujol, cm-1): ν(C≡C) 2073 (m), 1983 (m). 1H NMR
(CDCl3): δ 7.64-6.86 (m, 45H, Ph); 4.40 (s, 5H, Cp). 31P NMR (CDCl3): δ 51.2 (s,
Ru(PPh3)2); 33.9 (s, Au(PPh3)). Literature IR (Nujol, cm-1): ν(C≡C) 2072 (m), 1981
(m). 1H NMR (CDCl3): δ 7.59-7.08 (m, 45H, Ph); 4.38 (s, 5H, Cp). 31P NMR
(CDCl3): δ 49.9 (s, Ru(PPh3)2); 32.5 (s, Au(PPh3)).141
{Au(C≡CC≡C[Ru(dppe)Cp*])}2(µ-dppm) (26)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (100 mg, 0.15 mmol) in THF (5 mL) was
treated with n-BuLi (0.14 mL, 1.045 M solution in THF) and stirred for 1 h at -78oC.
(AuCl)2(µ-dppm) (60 mg, 0.07 mmol) was added and the reaction was allowed to
warm to r.t. over 2 h. Hexane (20 mL) was added and a yellow precipitate was
collected and washed with hexane to give {Au(C≡CC≡C[Ru(dppe)Cp*])}2(µ-dppm)
(26) (135 mg, 90%). Anal. Calcd. (C105H100P6Au2Ru2): C, 58.83; H, 4.70. Found: C,
134
58.88; H, 4.75. IR (Nujol, cm-1): ν(C≡C) 2106 (m); 1982 (m). 1H NMR (C6D6): δ
7.95-6.85 (m, 60H, Ph); 3.23 (s, 2H, CH2); 2.89-2.80, 1.92-1.81 (2 x m, 8H,
CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.76-127.64 (m, Ph); 93.12 (s,
C5Me5); 43.33 (s, CH2); 30.12-29.86 (m, CH2CH2); 10.08 (s, C5Me5). 31P NMR
(C6D6): δ 82.0 (s, dppe); 35.6 (s, dppm). ES-MS (+ve ion, CH3CN, m/z): 2143, [M -
H]+; 1460, [M - C4Ru(dppe)Cp*]+; 1366, [M - Au2(dppm)]+; 675,
[Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+.
Ru{C≡CC≡C[PtCl(PPh3)2]}(dppe)Cp* (27)
Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) and
Pt(PPh3)2Cl2 (59 mg, 0.07 mmol) gave Ru{C≡CC≡C[PtCl(PPh3)2]}(dppe)Cp* (27) as
a bright yellow powder (43 mg, 40%). Anal. Calcd. (C76H69P4PtClRu): C, 63.48; H,
4.84. Found: C, 63.60; H, 5.18. IR (Nujol, cm-1): ν(C≡C) 2105 (m), 1984 (m). 1H
NMR (C6D6): δ 8.02-6.83 (m, 50H, Ph); 2.39-2.20, 1.90-1.84 (2 x m, 2 x 2H,
CH2CH2); 1.54 (s, 15H, Cp*). 31P NMR (C6D6): δ 81.9 (s, Ru(dppe)); 22.2 (s,
Pt(PPh3)2). ES-MS (+ve ion, MeOH, m/z): 1437, [M+]; 1436, [M - H]+ ; 635,
[Ru(dppe)Cp*]+.
Ru(C≡CC≡CGePh3)(dppe)Cp* (28)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (5 mL) was
treated with n-BuLi (50 µL, 2.3 M solution in hexane) and stirred for 30 min at -78oC.
GeClPh3 (31 mg, 0.07 mmol) was added and the reaction was allowed to warm to r.t.
over 3 h. The solvent was then removed and the yellow residue extracted with hexane
(60 mL) and filtered via cannula. The solvent was evaporated to dryness to give
Ru(C≡CC≡CGePh3)(dppe)Cp* (28) as a yellow crystalline powder (62 mg, 82%).
Single crystals suitable for X-ray studies were grown from THF/hexane. Anal. Calcd.
(C58H54P2GeRu): C, 70.60; H, 5.52. Found: C, 70.61; H, 5.55. IR (Nujol, cm-1):
ν(C≡C) 2106 (m), 2000 (m). 1H NMR (C6D6): δ 7.85-6.89 (m, 35H, Ph); 2.53-2.50,
135
1.79-1.75 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ 137.76-
127.64 (m, Ph); 99.42, 93.46, 86.85, 62.40 (s, C1, C2, C3, C4); 93.22 (s, br, C5Me5);
30.12-29.62 (m, CH2CH2); 10.17 (s, C5Me5). 31P NMR (C6D6): δ 81.0 (s, dppe). ES-
MS (+ve ion, CH3CN, m/z): 1009, [M + Na]+; 988, [M + H]+; 675,
[Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+.
Ru(C≡CC≡CSnPh3)(dppe)Cp* (29)
Similarly, from Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) and SnClPh3 (45 mg,
0.11 mmol) was obtained Ru(C≡CC≡CSnPh3)(dppe)Cp* (29) as a yellow crystalline
powder (54 mg, 70%). Anal. Calcd. (C58H54P2SnRu): C, 67.45; H, 5.27. Found: C,
67.97; H, 5.51. IR (Nujol, cm-1): ν(C≡C) 2081 (m), 1977 (m). 1H NMR (C6D6): δ
7.89-7.01 (m, 35H, Ph); 2.55-2.52, 1.81-1.78 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H,
Cp*). 13C NMR (C6D6): δ 134.02-127.84 (m, Ph); 103.22, 99.05, 86.85, 74.82 (s, C1,
C2, C3, C4); 91.87 (s, C5Me5); 30.01-29.86 (m, CH2CH2); 10.21 (s, C5Me5). 31P NMR
(C6D6): δ 81.2 (s, dppe). ES-MS (+ve ion, CH3CN, m/z): 1033, [M]+; 675,
[Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+.
{Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*} (30)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.07 mmol) in THF (2 mL) was
treated with n-BuLi (0.14 mL, 1.045 M solution in THF) and stirred for 30 min at -
78oC. A solution of [CuCl(PPh3)]4 (28 mg, 0.07 mmol) in THF (5 mL) was added via
cannula and the reaction was allowed to warm to r.t. over 3 h. A red-orange
precipitate was collected and washed with hexane to give
{Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*} (30) (86 mg, 85%). Single
crystals suitable for X-ray studies were grown from CH2Cl2/hexane. IR (CH2Cl2, cm-
1): ν(C≡C) 2101 (m); 1949 (m). 1H NMR (C6D6): δ 7.75-7.03 (m, 40H, Ph); 2.55-
2.40, 2.00-1.89 (2 x m, 8H, CH2CH2); 1.53 (s, 30H, Cp*). 31P NMR (C6D6): δ 80.1 (s,
dppe). ES-MS (+ve ion, MeOH) (m/z): 1366, [M]+; 635, [Ru(dppe)Cp*]+. Literature
136
IR: ν(C≡C) 2107 (m); 1951 (m). 1H NMR: δ 7.66-7.09 (m, 40H, Ph); 2.67, 2.09 (2 x
m, 8H, CH2CH2); 1.49 (s, 30H, Cp*). 31P NMR: δ 80.0 (s, dppe). ES-MS (m/z): 1366,
[M]+; 635, [Ru(dppe)Cp*]+.12
{Cp(Ph3P)2Ru}(C≡CC≡C){Cu(PPh3)} (31)
A solution of Ru(C≡CC≡CH)(PPh3)2Cp (52 mg, 0.07 mmol), in THF (10 mL) was
treated with n-BuLi (0.14 mL, 1.045 M solution in THF) and stirred for 30 min at -
78oC. [CuCl(PPh3)]4 (25 mg, 0.07 mmol) was added and the reaction was allowed to
warm to r.t. over 2 h. The solvent was then removed. The residue was dissolved in
minimum CH2Cl2 and loaded onto a basic alumina column eluting with a 3:7
acetone/hexane mixture. A yellow band was collected and solvent removed to give
{Cp(Ph3P)2Ru}C≡CC≡C{Cu(PPh3)} (31) (30 mg, 40%). Anal. Calcd.
(C63H50P3RuCu): C, 71.04; H, 4.74. Found: C, 71.08; H, 4.79. IR (CH2Cl2, cm-1):
ν(C≡C) 2106 (m), 1994 (m). 1H NMR (C6D6): δ 7.76-6.89 (m, 45H, Ph); 4.24 (s, 5H,
Cp). 31P NMR (C6D6): δ 50.8 (s, Ru(PPh3)2), 38.5 (s, Cu(PPh3)). ES-MS (+ve ion,
MeOH, m/z): 1096, [M + MeOH]+; 691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.
{Cp(Ph3P)2Ru}(C≡CC≡C){Rh(CO)(PPh3)2} (32)
Similarly, {Cp(Ph3P)2Ru}(C≡CC≡C){Rh(CO)(PPh3)2} (32) was obtained as a yellow
powder (49 mg, 50%) from the reaction between Ru(C≡CC≡CH)(PPh3)2Cp (53 mg,
0.07 mmol) and RhCl(CO)(PPh3)2 (49 mg, 0.07 mmol). Anal. Calcd.
(C82H65OP4RhRu): C, 70.64; H, 4.70. Found: C, 70.73; H, 4.76. IR (CH2Cl2, cm-1):
ν(C≡C) 2108 (m), 1978 (m); ν(CO) 1955 (m). 1H NMR (C6D6): δ 7.17-6.92 (m, 60H,
Ph); 4.35 (s, 5H, Cp). 31P NMR (C6D6): δ 50.6 (s, Ru(PPh3)2), 38.5 (s, Rh(PPh3)2).
ES-MS (+ve ion, MeOH, m/z): 1394, [M]+; 691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.
Chapter Four
The Reactions of
Ru(C≡CC≡CLi)(dppe)Cp*
138
4.1. Introduction
4.1.1. The reaction of nucleophilic complexes with organic reagents
In 2001, the lithiated tungsten carbide Tp’(CO)2W(≡CLi) was generated from the
treatment of the complex Tp’(CO)2(W≡CH) with n-BuLi. Subsequently,
Tp’(CO)2W(≡CLi) was reacted with a range of electrophiles in order to trap the
anionic complex. First, it was reacted with iodomethane and iodine to give the
complexes Tp’(CO)2W(≡CMe) and Tp’(CO)2W(C≡CI) (Scheme 83).147
Tp'(OC)2W C Hn-BuLi
THFTp'(OC)2W C Li
-78oC
Tp'(OC)2W C MeTp'(OC)2W C I
I2 MeI
Scheme 83: The lithiation of Tp’(CO)2W(≡CH)
Then, Tp’(CO)2W(≡CLi) was reacted with other electrophiles such as benzophenone,
benzaldehyde and benzoyl bromide. The complexes Tp’(CO)2W[≡CCPh2(OH)],
Tp’(CO)2W[≡CHPh(OH)] and Tp’(CO)2W(≡CC(O)Ph) were obtained, respectively
(Scheme 84).147
Tp'(OC)2W C I
Tp'(OC)2W C C
Tp'(OC)2W C
R
OH
Ph
PhC
O
R = Ph or H
Ph Br
O
Ph R
O
H2O
1)
2)
Scheme 84: Reactions of Tp’(CO)2W(≡CLi) with electrophiles
139
Furthermore, Gladysz and co-workers reported the reaction of
Re(C≡CH)(NO)(PPh3)Cp* with n-BuLi to synthesise the lithium complex
Re(C≡CLi)(NO)(PPh3)Cp*.138 The nucleophilic complex was further reacted with
iodomethane to generate the methylated complex Re(C≡CMe)(NO)(PPh3)Cp*.
Similarly, the reaction of Re(C≡CC≡CH)(NO)(PPh3)Cp* with n-BuLi afforded
Re(C≡CC≡CLi)(NO)(PPh3)Cp*, which was trapped with iodomethane to give
Re(C≡CC≡CMe)(NO)(PPh3)Cp* (Scheme 85).22
C CRe
ON PPh3-80oC
n-BuLiH C CRe
ON PPh3
Li
C CRe
ON PPh3
Me
MeI
n n
n
n = 1, 2
Scheme 85: The synthesis of Re{(C≡C)nMe}(NO)(PPh3)Cp*
4.1.2. The reaction of nucleophilic complexes with polyfluoroaromatic reagents
The availability of polyfluoroaromatic compounds has resulted in many investigations
of their reactivity. It is now well known that fluorocarbons have increased
susceptibility to nucleophilic attack owing to withdrawal of electron density onto the
fluorine atoms.148
In 1967, Wiles and Massey reported the synthesis of several fluoroaromatic
acetylenes using the lithium derivatives of mono-substituted alkynes (Scheme 86).149
The acetylene group introduced activates the fluorine atom para to it, so that
RC≡C(C6F5) reacted further to give the disubstituted compounds 1,4-(RC≡C)2C6F4 in
high yield (Scheme 86).149
140
R C C H R C C Li
R C C C6F5R C C Li
R C C C6F4 RCC
BuLiTHF
C6F6
+
R = H, Ph, SiEt3
Scheme 86: The synthesis of RC≡C(C6F5) and 1,4-(RC≡C)2C6F4
The complexes Ru(C≡CC6F5)(dppe)Cp* and Ru(C≡CC6F5)(dppe)Cp were synthesised
by a different method.55 The trimethylsilyl-substituted alkyne, TMS(C≡C)C6F5, reacts
with the chlororuthenium complex in the presence of potassium fluoride (Scheme 87).
Similarly, the diruthenium complexes 1,4-{Cp(PPh3)2Ru(C≡C)}2C6F4 and 1,4-
{Cp(dppe)Ru(C≡C)}2C6F4 were obtained from the reactions of 1,4-
{TMS(C≡C)}2C6F4 under the same conditions (Scheme 88).55
TMS C C C6F5 Cp'(dppe)Ru C C C6F5+KF
MeOH∆ Cp' = Cp* or Cp
RuCl(dppe)Cp'
Scheme 87: The synthesis of Ru(C≡CC6F5)(dppe)Cp’
TMS C C C6F4 +KF
THF/MeOH∆
[Ru] C C C6F4 [Ru]CC[Ru]Cl
[Ru] = Ru(dppe)Cp or Ru(PPh3)2Cp2
Scheme 88: The synthesis of 1,4-{[Ru](C≡C)}2C6F4
4.1.3. The nucleophilic ruthenium(II) complex Ru(C≡CC≡CLi)(dppe)Cp*
In Chapter Three, the ruthenium(II) diynyl complex Ru(C≡CC≡CH)(dppe)Cp* was
successfully lithiated with a strong base n-BuLi, which resulted in the formation of a
nucleophilic complex Ru(C≡CC≡CLi)(dppe)Cp*. This complex was further reacted
with metal halides to afford new asymmetric ruthenium(II) diyndiyl complexes
(Scheme 89).
141
C C C C Hn-BuLi
THF-78oC
C C C CRu
Ph2P PPh2
Ru
Ph2P PPh2
{MLn}Cl
in situ
C C C C {MLn}Ru
Ph2P PPh2
Li
Scheme 89: The lithiation and metalation of Ru(C≡CC≡CH)(dppe)Cp*
This reaction has allowed the formation of a new nucleophilic species,
Ru(C≡CC≡CLi)(dppe)Cp*. This complex shows similar characteristics to the
complexes Tp’(CO)2W(≡CLi), Re(C≡CLi)(NO)(PPh3)Cp* and
Re(C≡CC≡CLi)(NO)(PPh3)Cp* described previously. Hence, it can be proposed that
Ru(C≡CC≡CLi)(dppe)Cp* will react similarly with a range of electrophiles and
therefore be a precursor for new complexes for which the parent alkynes are either not
available or synthesised with difficulty.
142
4.2. Aim of this work
In this chapter, the reactivity of the lithium complex Ru(C≡CC≡CLi)(dppe)Cp*
synthesised in Chapter Three is further investigated. The nucleophilic nature of this
complex makes it a valuable starting material. Hence, the primary aim of this work
was to react Ru(C≡CC≡CLi)(dppe)Cp* with a range of electrophiles such as organic
substrates or polyfluoroaromatic compounds and to analyse and characterise the
products obtained.
143
4.3. Results and Discussion
4.3.1. Reactions with organic reagents
All the complexes described in this Section were fully characterised by 1H, 31P and 13C NMR, IR, ES-MS and microanalysis and the data are summarised in Table 17.
4.3.1.1. Synthesis of Ru(C≡CC≡CMe)(dppe)Cp*
Ru(C≡CC≡CH)(dppe)Cp* was treated with two equivalents of n-BuLi at -78oC. After
stirring for 30 min, iodomethane was added to the solution, which was then allowed to
warm to room temperature. After work-up, the complex Ru(C≡CC≡CMe)(dppe)Cp*
(33) was obtained in 70% yield (Scheme 90).
C C C C Hn-BuLi
THF-78oC
C C C CRu
Ph2P PPh2
Ru
Ph2P PPh2
MeI
in situ
C C C C MeRu
Ph2P PPh2
Li
(33)
Scheme 90: The synthesis of Ru(C≡CC≡CMe)(dppe)Cp* (33)
In the 1H, 31P and 13C NMR spectra of complex 33, the characteristic peaks for the
Ru(dppe)Cp* ligand are observed. The methyl group is characterised by a singlet δ
1.73 in the 1H NMR spectrum and a singlet at δ 21.03 in the 13C NMR spectrum. The
resonances for the carbon atoms of the C4 chain are also present in the 13C NMR at δ
124.69, 91.73, 76.86 and 52.46. Two ν(C≡C) bands at 2029 and 1908 cm-1 were
144
observed in the infrared spectrum. Further characterisation of 33 was obtained from
an ES-MS which contained ions corresponding to [M + MeOH]+ at m/z 732 and at m/z
635 for [Ru(dppe)Cp*]+.
Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane. The
ORTEP plot of compound 33 is shown in Figure 48 and selected bond distances and
angles are given in Table 16. The Ru-C(1) bond length of 2.029(3) Å is close to the
value expected for a ruthenium carbon single bond (2.01 Å). The C(1)-C(2) bond
length is equal to 1.166(4) Å, the C(3)-C(4) distance is 1.193(5) Å, the C(2)-C(3)
distance is 1.419(5) Å, and the C(4)-C(5) distance is 1.472(5) Å. They are therefore
consistent with being C≡C triple and C-C single bonds, respectively. The carbon
chain in 33 is essentially linear, the angles C(1)-C(2)-C(3), C(2)-C(3)-C(4) and C(3)-
C(4)-C(5) being 173.9(3) o, 177.8(4) o and 175.9(4) o, respectively.
Bond distances (Å) Bond Angles (o)
Ru-C(1) 2.029(3) Ru-C(1)-C(2) 177.8(3)
Ru-P(1) 2.262(7) P(1)-Ru-P(2) 82.6(3)
Ru-P(2) 2.273(9) P(1)-Ru-C(1) 82.3(8)
Ru-C(Cp*) 2.233(4) - 2.271(3) P(2)-Ru-C(1) 86.0(1)
Ru-C(Cp*) (av.) 2.259(3) C(1)-C(2)-C(3) 173.9(3)
C(1)-C(2) 1.166(4) C(2)-C(3)-C(4) 177.8(4)
C(2)-C(3) 1.419(5) C(3)-C(4)-C(5) 175.9(4)
C(3)-C(4) 1.193(5)
C(4)-C(5) 1.472(5)
C(5)-H(5A) 0.953(4)
C(5)-H(5B) 0.966(5)
C(5)-H(5C) 0.951(5)
Table 15: Selected bond distances (Å) and angles (o) for 33
145
Figure 48: ORTEP view of 33
4.3.1.2. Synthesis of Ru{C≡CC≡CC(O)Ph}(dppe)Cp*
Benzoyl chloride is susceptible to nucleophilic attack at the carbonyl carbon. Hence,
the reaction of Ru(C≡CC≡CLi)(dppe)Cp* with benzoyl chloride was attempted. First,
Ru(C≡CC≡CLi)(dppe)Cp* was generated in situ as described previously. Then,
benzoyl chloride was added at -78oC and an immediate colour change from yellow to
red was observed. The complex Ru{C≡CC≡CC(O)Ph}(dppe)Cp* (34) was obtained
in 75% yield as a red powder. A proposed mechanism for the reaction involves the
attack of the anion Ru(C≡CC≡C-)(dppe)Cp* at the carbonyl carbon. The intermediate
formed then loses the chloride to form complex 34 which possesses a ketone
substituent (Scheme 91).
The same trend as complex 33 is observed in the 1H, 31P and 13C NMR spectra with
the presence of peaks for the Ru(dppe)Cp*C4 fragment. The CO group is
characterised by a singlet at δ 206.41 in the 13C NMR spectrum and one ν(CO) band
at 1716 cm-1 in the IR spectrum. The phenyl groups are present as multiplets at δ
7.28-7.05 and 133.63-127.63 in the 1H and 13C NMR spectra, respectively. Finally the
ES-MS contains [M + Na]+ at m/z 811, [M]+ at m/z 788 and [Ru(dppe)Cp*]+ at m/z
635.
146
CC C C C
O
Ph
Ph Cl
O
C C C C C Cl
Ph
O
C C C C Hn-BuLi
THFC C C C Li
- LiCl
-78oC
Ru
Ph2P PPh2
Ru
Ph2P PPh2
Ru
Ph2P PPh2
Ru
Ph2P PPh2 (34)
Scheme 91: Proposed mechanism for the synthesis of complex 34
4.3.1.3. Synthesis of Ru{C≡CC≡CC(O)Me}(dppe)Cp*
Similarly, the reaction of Ru(C≡CC≡CLi)(dppe)Cp* with acetyl chloride afforded the
complex Ru{C≡CC≡CC(O)Me}(dppe)Cp* (35) as a bright yellow crystalline powder.
The reaction is similar to that giving complex 34 since both reactions involved the
reaction of the nucleophilic Ru(C≡CC≡CLi)(dppe)Cp* with an acid chloride (Scheme
92).
CC C C C
O
MeRu
Ph2P PPh2
Me Cl
O
C C C C LiTHF
-78oC
Ru
Ph2P PPh2 (35)
Scheme 92: The synthesis of complex 35
The 1H NMR spectrum of complex 35 shows the presence of a singlet at δ 2.14 for the
protons of the methyl group. In the 13C NMR of 35, the resonance for the CO group
was found as a singlet at δ 201.57 while the resonance for the methyl group was
present as a singlet at δ 33.35. The IR spectrum of 35 also confirms the presence of
the CO group with a ν(CO) band at 1710 cm-1. In the ES-MS, a [M]+ ion was found at
m/z 725 with a [Ru(dppe)Cp*]+ fragment ion at m/z 635.
147
4.3.1.4. Synthesis of Ru{C≡CC≡CC(O)OMe}(dppe)Cp*
The complex Ru{C≡CC≡CC(O)OMe}(dppe)Cp* (36) was obtained from the reaction
of Ru(C≡CC≡CLi)(dppe)Cp* with methyl chloroformate as a yellow powder in 40%
yield (Scheme 93).
CC C C C
O
OMeMeO Cl
O
C C C C LiTHF
-78oC
Ru
Ph2P PPh2
Ru
Ph2P PPh2 (36)
Scheme 93: The synthesis of complex 36
The presence of the Ru(dppe)Cp* fragment is confirmed in the 1H and 31P NMR
spectra of complex 36. The OMe group is characterised by one singlet at δ 1.68 in the 1H NMR spectrum, which is unusual when compared to purely organic methyl esters.
One ν(CO) band at 1723 cm-1 is also present in the IR spectrum. The ES-MS
confirmed the formulation of this complex, containing [M]+ at m/z 743 and one
fragment ion at m/z 635 corresponding to [Ru(dppe)Cp*]+. Due to the poor yields and
instability of this complex in concentrated solutions it could not be satisfactorily
characterised by 13C NMR or microanalysis.
4.3.1.5. Synthesis of {Ru(C≡CC≡C)(dppe)Cp*}2(CO)2
Two equivalents of Ru(C≡CC≡CH)(dppe)Cp* dissolved in THF were treated with n-
BuLi at -78oC. Oxalyl choride was then added to Ru(C≡CC≡CLi)(dppe)Cp*
generated in situ and the colour of the solution changed from yellow to bright orange.
After warming up to room temperature and work-up the complex
{Ru(C≡CC≡C)(dppe)Cp*}2(CO)2 (37) was obtained in 55% yield as an orange
powder (Scheme 94).
148
C C LiRu
Ph2P PPh2
2 THF-78oC
Cl Cl
O
O
C CRu
Ph2P PPh2
2 CC Ru
PPh2Ph2P
2C
O
C
O(37)
Scheme 94: The synthesis of complex 37
The presence of the CO groups is confirmed by a singlet at δ 213.74 in the 13C NMR
spectrum and one ν(CO) band at 1655 cm-1 in the IR spectrum of complex 37. In the 1H and 13C NMR spectra, the resonances for the Ru(dppe)Cp* ligands are present as
described for previous complexes. The 31P NMR spectrum shows one resonance at δ
80.1 for the equivalent phosphorus atoms on the dppe ligands. The ES-MS confirmed
the formulation of 37 with [M + MeOH]+ at m/z 1453.
4.3.1.6. Synthesis of Ru{C≡CC≡CCHPh(OH)}(dppe)Cp*
Furthermore, Ru(C≡CC≡CH)(dppe)Cp* was treated with n-Buli at -78oC and
Ru(C≡CC≡CLi)(dppe)Cp* generated in situ was further reacted with benzaldehyde.
An immediate colour change from yellow to bright orange was observed and the
reaction was then quenched with water. The complex
Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* (38) was obtained in 76% yield. The proposed
mechanism involves the attack of the anionic complex Ru(C≡CC≡C-)(dppe)Cp* on
the carbonyl carbon of benzaldehyde. The intermediate is then protonated with water
to afford complex 38 (Scheme 95).
149
Ph H
O
C C C C C H
Ph
O
C C C C Hn-BuLi
THFC C C C Li
C C C C C H
Ph
OH- LiOH
-78oC
H O H
Ru
Ph2P PPh2
Ru
Ph2P PPh2
Ru
Ph2P PPh2
Ru
Ph2P PPh2
(38)
Scheme 95: Proposed mechanism for the formation of complex 38 Similarly to the previous complexes, the 1H, 31P and 13C NMR spectra of complex 38
show the presence of the Ru(dppe)Cp*C4 moiety. In the 1H NMR spectrum, the
presence of the OH group is characterised by a singlet at δ 5.52 while the proton on
the CH group is present as a singlet at δ 1.66. The infrared spectrum also shows one
ν(OH) band at 3303 cm-1. The 13C NMR spectrum of 38 shows one singlet at δ 79.89
which is assigned to the terminal carbon C(H)PhOH. The ES-MS of 38 contains a [M
+ Na]+ at m/z 813, a [M]+ ion at m/z 790 and one fragmentation ion at m/z 635
[Ru(dppe)Cp*]+.
150
C C C C Li[Ru*]
IMe
C C C C Me[Ru*]
Me Cl
O
C C C C[Ru*] C
O
Me
Ph Cl
O
C C C C[Ru*] C
O
Ph
MeO Cl
O
C C C C[Ru*] C
O
OMe
C C[Ru*] 2 CC [Ru*]2C
O
Ph H
O
C C C C C H
Ph
OH
[Ru*]
[Ru*] = Ru(dppe)Cp*
(37)
(38)
(33)
(36)
(35)
(34)
Cl Cl
O
O
C
O
Figure 49: Summary of products synthesised
151
Complex IR (cm-1) 1H NMR (δ) 13C NMR (δ) 31P NMR (δ) ES-MS (m/z) 33 ν(C≡C)
2029, 1908 7.28-6.89 (m, 20H, Ph); 2.65-2.62, 2.01-1.87 (2 x m, 2 x 2H, CH2CH2); 1.73 (s, 3H, CH3); 1.60 (s, 15H, Cp*)
133.96-127.42 (m, Ph); 124.69, 91.73, 76.86, 52.46 (s, C1, C2, C3, C4); 93.25 (s, C5Me5); 29.88-29.27 (m, CH2CH2); 21.03 (s, CH3); 10.12 (s, C5Me5)
81.6 (s, dppe) 731, [M + MeOH]+; 635,
Ru(dppe)Cp*]+
34 ν(C≡C) 2109, 2000; ν(CO) 1716
7.28-7.05 (m, 25H, Ph); 2.54-2.50, 2.18-2.08 (2 x m, 2 x 2H, CH2CH2); 1.51 (s, 15H, Cp*)
206.41 (s, CO); 133.63-127.63 (m, Ph); 112.17, 101.00, 95.59, 63.08 (s, C1, C2, C3, C4); 94.13 (t, 2J(CP) 2 Hz, C5Me5); 30.12-29.23 (m, CH2CH2); 10.02 (s, C5Me5)
80.5 (s, dppe) 811, [M + Na]+; 788, [M]+;
635, [Ru(dppe)Cp*]+
35 ν(C≡C) 2048
(m), 2004 (m); ν(CO) 1710 (m)
7.23-7.02 (m, 20H, Ph); 2.68-2.61, 1.85-1.78 (2 x m, 2 x 2H, CH2CH2); 2.14 (s, 3H, C(O)CH3); 1.58 (s, 15H, Cp*)
201.57 (s, CO); 134.51-126.96 (m, Ph); 121.86, 119.52, 102.13, 90.15 (s, C1, C2, C3, C4); 94.38 (s, C5Me5); 33.35-33.29 (m, C(O)CH3); 30.83-30.13 (m, CH2CH2); 10.83 (s, C5Me5)
81.7 (s, dppe) 725, [M]+; 635, [Ru(dppe)Cp*]+
36 ν(C≡C) 2008, 197; ν(CO) 1723
7.26-7.02 (m, 20H, Ph); 2.43-2.38, 2.13-2.06 (2 x m, 2 x 2H, CH2CH2); 1.68 (s, 3H, C(O)CH3); 1.53 (s, 15H, Cp*)
80.6 (s, dppe) 743, [M]+; 635,
[Ru(dppe)Cp*]+
37 ν(C≡C) 2095 (m), 1999 (m); ν(CO) 1655
7.99-6.89 (m, 24H, Ph); 2.20-2.14, 2.02-1.91 (2 x m, 2 x 2H, CH2CH2); 1.59 (s, 15H, Cp*)
213.74 (s, CO); 133.80-127.61 (m, Ph); 123.62, 100.28, 69.53, 55.62 (s, C1, C2, C3, C4); 90.62 (s, C5Me5); 30.01-29.75 (m, CH2CH2); 9.94 (s, C5Me5)
80.1 (s, dppe) 1453, [M + MeOH]+; 635, [Ru(dppe)Cp*]+
38 ν(OH) 3303 (w); ν(C≡C) 2106 (m), 2000 (m)
7.29-7.03 (m, 25H, Ph); 5.52 (s, 1H, OH); 2.58-2.56, 1.80-1.74 (2 x m, 2 x 2H, CH2CH2); 1.66 (s, 1H, CH); 1.57 (s, 15H, Cp*)
133.74-127.68 (m, Ph); 122.10, 99.22, 88.72, 65.85 (s, C1, C2, C3, C4); 93.24 (s, br, C5Me5); 79.89 (s, C(H)PhOH); 29.90-29.29 (m, CH2CH2); 10.07 (s, C5Me5)
81.3 (s, dppe) 813, [M + Na]+; 790, [M]+;
635, [Ru(dppe)Cp*]+
Table 16: Spectroscopic data for complexes 33 - 38
152
4.3.1.7. Reaction with TCNE
TCNE is an electron deficient alkene and is a very useful reagent since it undergoes
reaction with the electron rich carbon-carbon triple bonds of transition-metal alkynyl
complexes to give cyclobutenyl complexes and subsequent ring-opening to buta-1,3-
dien-2-yl complexes.116,117
The complex Ru(C≡CC≡CLi)(dppe)Cp* was reacted with one equivalent of TCNE in
THF at -78oC. The colour changed immediately from yellow to dark green. After
purification, {Ru(dppe)Cp*}2{µ-C≡CC[=C(CN)2]C[=C(CN)2]C≡C} (39) was isolated
as the major product in 32% yield. The proposed mechanism for the synthesis of
complex 39 is shown in Scheme 96. The reaction is suggested to undergo [2 + 2]-
cycloaddition, followed by ring opening. This intermediate then attacked the β-carbon
of Ru(C≡CC≡CLi)(dppe)Cp* and elimination of lithium acetylide gives complex 39.
C[Ru*] C C
C
LiC
C
NC CNCN CN
C[Ru*]C C
C
C
C
NC CNCN CN
CC
[Ru*]
[Ru*] LiC C C C
C C
NCNC CN
CN
[Ru*] LiC C C C
[Ru*]Li CCCC
-Li2C2
THF
TCNE
[Ru*] = Ru(dppe)Cp* -78oC
(39)
Scheme 96: The reaction of Ru(C≡CC≡CLi)(dppe)Cp* with TCNE
Complex 39 was previously synthesised from the reaction of
{Cp*(dppe)Ru}2(C≡CC≡CC≡C) with TCNE in CH2Cl2 at room temperature. An X-
ray crystal structure was also reported and showed that complex 39 is bent due to the
presence of the C=C double bonds.12 As expected, the spectroscopic features of 39
were similar to those found previously.12 The 1H NMR spectrum contained typical
153
peaks for the Ru(dppe)Cp* moieties. The 31P NMR shows two doublets at δ 81.3 (d, 3J(PP) 13 Hz) and at δ 79.9 (d, 3J(PP) 13 Hz) which corresponds to the two
magnetically inequivalent phosphorus atoms of each dppe ligand. The most
interesting feature in the infrared spectrum is the appearance of two ν(CN) bands at
2208 and 2075 cm-1. The ES-MS of 39 shows a peak for the molecular ion [M+ Na]+
at m/z 1493 and a fragment ion corresponding to [Ru(dppe)Cp*]+ at m/z 635.
From the same reaction, another product was collected and characterised by X-ray
crystallography and spectroscopically. Ru{C≡CC3NH(CN)(CO)=C(CN)2}(dppe)Cp*
(40) was obtained as a blue band in 20% yield. A possible mechanism for the
formation of 40 is shown in Scheme 97.
C CNH2
CN
O
NC CN
Ru
Ph2P PPh2
C CNH2
CNO
NC CN
Ru
Ph2P PPh2
C C C
C H
C
NC
NC CN
Ru
Ph2P PPh2
C C C C LiTCNE
THF-78oC
Ru
Ph2P PPh2
CN
H
C CNH
CN
O
NC CN
Ru
Ph2P PPh2 H
(40)
Scheme 97: Proposed mechanism for the synthesis of complex 40
154
The 31P NMR spectrum of complex 40 shows one singlet at δ 72.9 assigned to the
phosphorus nuclei bonded to the ruthenium and the 1H NMR spectrum shows the
characteristic peaks for the Ru(dppe)Cp* group. The infrared spectrum of 40 also
contains ν(NH) at 3058 cm-1, ν(C≡C) at 1954 cm-1, ν(C=C) at 1603 cm-1, a broad
ν(CN) at 2212 cm-1 and ν(CO) at 1716 cm-1. The ES-MS of 40 contains fragment
ions corresponding to [Ru(dppe)Cp*C2]+ at m/z 659 and [Ru(dppe)Cp*]+ at m/z 635.
A high resolution mass spectrum of 40 was also obtained. The molecular formula
found was C46H40N4NaOP2Ru which corresponds to [M + Na]+ at m/z 851.1624
(calcd. 851.1626). These values are very close to each other confirming the
formulation of complex 40.
Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane. Figure 50
shows the ORTEP plot of compound 40, while selected structural data are collected in
Table 18. The Ru-C(1) bond length of 1.96(1) Å is close to the value expected for a
ruthenium carbon single bond (2.01 Å). The C(1)-C(2) bond length is equal to 1.22(1)
Å which is consistent with C≡C triple bond and the C(2)-C(3) bond length is equal to
1.43(1) Å due to a C-C single bond. The C(6)-O(6) bond length is equal to 1.26(1) Å
which is consistent with being a C=O group. The angles Ru-C(1)-C(2) [175.2(8) o],
C(1)-C(2)-C(3) [166.9(1) o] in 40 are close to linear whereas the C(2)-C(3)-C(4)
[124.8(1) o] angle is bent.
Figure 50: ORTEP view of complex 40
155
Bond distances (Å) Bond Angles (o)
Ru-C(1) 1.960(1) Ru-C(1)-C(2) 175.2(8)
Ru-P(1) 2.302(2) P(1)-Ru-P(2) 81.6(9)
Ru-P(2) 2.272(3) P(1)-Ru-C(1) 85.5(3)
Ru-C(Cp*) 2.235(9) - 2.29(1) P(2)-Ru-C(1) 89.1(3)
Ru-C(Cp*) (av.) 2.264(9) C(1)-C(2)-C(3) 166.9(1)
C(1)-C(2) 1.220(1) C(2)-C(3)-C(4) 124.8(1)
C(2)-C(3) 1.430(1) C(2)-C(3)-C(7) 129.1(1)
C(3)-C(4) 1.420(1) C(4)-C(3)-C(7) 106.1(1)
C(3)-C(7) 1.430(1)
C(6)-O(6) 1.260(1)
C(71)-N(71) 1.140(1)
Table 17: Selected bond distances (Å) and angles (o) for complex 40
Finally, from the same reaction another minor product was collected as a bright
orange band in 16% yield and characterised as
Ru{C≡CC4N(NH)H(Me)C(CN)2)}(dppe)Cp* (41) (Figure 51).
C CRu
Ph2P PPh2N
NH
CH3
NC
CN
Figure 47: Representation of complex 41
Elemental analyses and the ES-MS confirmed the formulation of this complex,
supported by spectroscopic data. A ν(NH) band at 3060 cm-1, a ν(C≡C) band at 2024
cm-1, a ν(CH) band at 2926 cm-1, a ν(CN) band at 2204 cm-1 and a ν(C=C) band at
1644 cm-1 were observed in the IR spectrum. In the 1H NMR spectrum, resonances for
156
the aromatic protons, the dppe and Cp* ligands are present as for complex 40. Three
singlets at δ 4.19 for NH group, at δ 2.17 for the methyl group and at δ 1.26 for the
CH group are also present. Further characterisation of 41 was obtained from an ES-
MS which contained the molecular ion [M]+ at m/z 816 and one fragment ion at m/z
635 for [Ru(dppe)Cp*]+. A high resolution mass spectrum of 41 was also obtained.
The molecular formula found was C46H45N4P2Ru which corresponds to a [M + H]+ at
m/z 817.211 (calcd. 817.216). Thus, these values are close to each other confirming
the formulation of complex 41.
The structure of complex 41 was determined from an X-ray structure determination of
crystals obtained after recrystallisation from CH2Cl2/hexane (Figure 52). Selected
structural data are collected in Table 19. The Ru-C(1) bond length of 1.962(2) Å is
consistent with the value for a ruthenium carbon single bond. The C(1)-C(2) bond
length is equal to 1.232(3) Å which is consistent with C≡C triple bond and the C(2)-
C(3) bond length is equal 1.388(4) Å due to a C-C single bond. The carbon chain in
41 is essentially linear, with angles Ru-C(1)-C(2) equal to 178.3(2) o and C(1)-C(2)-
C(3) equal to 168.3(3) o.
Figure 52: ORTEP view of complex 41
157
Bond distances (Å) Bond Angles (o)
Ru-C(1) 1.962(2) Ru-C(1)-C(2) 178.3(2)
Ru-P(1) 2.273(6) P(1)-Ru-P(2) 83.9(2)
Ru-P(2) 2.287(6) P(1)-Ru-C(1) 81.8(7)
Ru-C(Cp*) 2.220(2) - 2.284(2) P(2)-Ru-C(1) 87.4(7)
Ru-C(Cp*) (av.) 2.255(2) C(1)-C(2)-C(3) 168.3(3)
C(1)-C(2) 1.232(3) C(2)-C(3)-C(8) 135.7(3)
C(2)-C(3) 1.388(4) C(2)-C(3)-N(4) 109.4(3)
C(3)-C(8) 1.284(4) C(8)-C(3)-N(4) 114.8(3)
C(3)-N(4) 1.457(4)
Table 18: Selected bond distances (Å) and angles (o) for complex 41
The mechanism for the formation of 41 is not obvious. However, the analysis of the
structure of 41 suggests that the insertion of one TCNE occurred (presence of 4
nitrogens). If it is assumed that the TCNE insertion was at the terminal carbons, then
the first step of the reaction can be the usually described [2 +2]-cycloaddition of
TCNE to the carbon chain which is then followed by ring opening (Scheme 98).
TCNE
[Ru*] = Ru(dppe)Cp*
[Ru*] LiC C C C
C C
NCNC CN
CN
Intermediate
[Ru*] LiC C C C C[Ru*] C C
C Li
C
NC
NC CN
CN
Scheme 98: Proposed first step for the synthesis of 41
However, this intermediate must have reacted further to give complex 41. It is not
known if this occurred during the reaction or during the isolation of the product on
TLC plates. These plates are acidic and could have been a factor in the synthesis of
the two different complexes 40 and 41. In order to eliminate this possibility, the
method for the isolation of the product from this reaction should be changed.
Furthermore, isotopic labeling of the carbon atoms of the chain of
Ru(C≡CC≡CH)(dppe)Cp* would allow identification of the position of these carbons
in the final product. In particular, the labeling of C3 and C4 should give a doublet in
158
the 13C NMR if they are sequential in the product. Similarly, the two central carbons
of TCNE could be labeled and analysis of their positions in the final product should
give an indication on how the reaction proceeded. This could also give an explanation
for the presence of the CH3 group. Two possibilities for its formation can be
proposed: the carbon corresponds to the initial carbon chain of
Ru(C≡CC≡CH)(dppe)Cp* which has undergone fragmentation or it can come from
the THF used as solvent in the reaction. In order to refute this, the reaction should be
done in different solvents. In addition, the complex
Ru(C≡CC[=C(CN)2]CH[=C(CN)2])(dppe)Cp* was previously obtained from the
reaction of Ru(C≡CC≡CH)(dppe)Cp* with TCNE.150 This complex could be
dissolved in THF and the reaction could be monitored to determine if complex 41 is
formed from it. If not, the reaction mixture could be put on TLC plates and if complex
41 is obtained this will indicate that its formation is due to the isolation technique
used.
4.3.2. Reactions with polyfluoroaromatic reagents
In the Introduction, it was described that polyfluoroaromatic compounds are
susceptible to nucleophilic substitution. Hence, it was suggested that the nucleophilic
complex Ru(C≡CC≡CLi)(dppe)Cp* should readily react with these compounds. All
the compounds described in this Section were fully characterised by 1H, 31P and 13C
NMR, IR, ES-MS and microanalysis and the data are summarised in Table 21.
4.3.2.1. Synthesis of Ru(C≡CC≡CC6F5)(dppe)Cp*
The first step of the reaction involved the generation in situ of
Ru(C≡CC≡CLi)(dppe)Cp* from the treatment of Ru(C≡CC≡CH)(dppe)Cp* with n-
BuLi at -78oC. Hexafluorobenzene was then added and an immediate colour change
from yellow to orange was observed. Ru(C≡CC≡CC6F5)(dppe)Cp* (42) was obtained
as an orange crystalline powder in 80% yield. The reaction is assumed to involve the
addition of the attacking nucleophile to the C6F6 ring to form a negatively charged
intermediate and F- is then eliminated in the second step. This is an example of a
nucleophilic aromatic substitution (Scheme 99).
159
C C C C
C C C C Li F
F F
F
FF
F F
F
FF
F F
F
FFF
F F
FF
F F
F F
F
FF
- F-
Ru
Ph2P PPh2
C C C CRu
Ph2P PPh2F
Ru
Ph2P PPh2
C C C CRu
Ph2P PPh2
C C C CRu
Ph2P PPh2(42)
Scheme 99: Proposed mechanism for the synthesis of 42
The characteristic peaks for the Ru(C4)(dppe)Cp* fragment are present in the 1H, 31P
and 13C NMR spectra of complex 42. In the infrared spectrum, two bands for the ν(C-
F) stretch were present at 1376 and 1261 cm-1. The ES-MS of 42 shows a peak for the
[M + Na]+ ion at m/z 873 and one fragmentation ion corresponding to [Ru(dppe)Cp*]+
at m/z 635.
In the 19F NMR spectrum, three resonances are observed from the AA’MXX’spin
system. The meta and ortho fluorines of 42 are observed as multiplets at δ -166.63 – -
166.72 and -141.40 – -141.46, respectively. The para fluorine is observed as a triplet
at δ -161.79, due to coupling with the meta fluorines, with a coupling constant of 22
Hz which is also reflected in the meta fluorine resonances. A 19F COSY NMR of 42
was obtained and is shown in Figure 53. There are two main cross-peaks in the
spectrum. The peak for the meta fluorine at δ -166.63 – -166.72 is coupled to the para
fluorine at δ -161.79 and to the ortho fluorine at δ -141.40 – -141.46.
160
Figure 53: 19F COSY NMR of complex 42
The structure of 42 was confirmed by X-ray studies of crystals grown from
CH2Cl2/hexane (Figure 54). Selected structural data are collected in Table 22. The
Ru(dppe)Cp* fragment has the expected geometry, with Ru-P(1) and Ru-P(2) equals
to 2.281(1) Å and 2.270(3) Å, respectively and the Ru-C(Cp*) distances of 2.180(2) -
2.35(1) Å. The Ru-C(1) bond length of 1.993(8) Å is close to the value expected for a
ruthenium carbon single bond (2.01 Å). The C(1)-C(2) bond length is equal to 1.18(1)
Å, the C(2)-C(3) distance is 1.39(1) Å and the C(3)-C(4) distance is 1.21(1) Å. The
expected alternating short C(1)-C(2), long C(2)-C(3) and short C(3)-C(4) bonds are
consistent with the diynyl nature of the bonds. The C(4)-C(41) distance is equal to
161
1.45(1) Å, reflecting the presence of a single bond. The average length for the C(n)-
F(n) (n = 42 - 46) bond is equal to 1.34(1) Å. The angles Ru-C(1)-C(2) [175.1(9) o],
C(1)-C(2)-C(3) [170.5(8) o] and C(2)-C(3)-C(4) [179.2(8)o] and C(3)-C(4)-(C41)
[166.4(1) o] indicates that the carbon chain in 42 is essentially linear.
Figure 54: ORTEP view of complex 42
4.3.2.2. Synthesis of Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp*
Complex Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* (43) was obtained from a similar
reaction, where Ru(C≡CC≡CLi)(dppe)Cp* was reacted with the compound C6F5NO2.
This reaction is an example of a C-F cleavage occurring on the fluoroarene C6F5NO2.
Complex 43 was obtained as a purple powder in 80% yield (Scheme 100).
NO2C C C CC6F5NO2
Ru
Ph2P PPh2
Li
THF-78oC C C C C
F F
NO2
FF
Ru
Ph2P PPh2 (43)
Scheme 100: The synthesis of 43
The NMR spectroscopic analyses of complex 43 confirmed the presence of the
Ru(dppe)Cp* ligand. The IR spectrum contains a broad ν(NO) band at 1634 cm-1 and
162
two ν(C-F) bands at 1259 and 1016 cm-1. Elemental analysis and the ES-MS
confirmed the formulation of complex 43 with [M]+ found at m/z 878.
In the 19F NMR the ortho and meta fluorines form a AA’XX’ spin system and are
found as multiplets at δ -140.26 – -140.34 and -151.88 – -151.96. This is consistent
with 1,4 substitution.
4.3.2.3. Synthesis of Ru(C≡CC≡CC6F4CN-4)(dppe)Cp*
C6F5CN is another available fluoroarene which contains an electron-withdrawing CN
substituent. Hence, Ru(C≡CC≡CLi)(dppe)Cp* was reacted with C6F5CN and an
immediate colour change from yellow to bright orange was observed. After work-up,
Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* (44) was obtained in 90% yield (Scheme 101).
C C C CC6F5CN
Ru
Ph2P PPh2
Li
THF-78oC
C C C C
F F
CN
FF
Ru
Ph2P PPh2 (44)
Scheme 101: The synthesis of 44 Similarly to complexes 42 and 43, the 1H, 31P and 13C NMR spectra of complex 44
show the presence of the Ru(dppe)Cp* unit and the carbons of the chain. The 13C
NMR of complex 44 also shows the presence of one resonance for the CN group
found as a singlet at δ 111.21. The infrared spectrum contains one band at 2214 cm-1
due to ν(CN) stretch and two bands at 1380 and 1264 cm-1 are present for the ν(C-F)
stretch.
In the 19F NMR, two multiplets at δ -138.72 – -138.83 and -139.68 – -139.79 are
observed and correspond to the two sets of equivalent fluorine atoms, as expected due
to the 1,4-substitution. The structure of 44 was also confirmed by the ES-MS which
contains [M + H]+ at m/z 858 and the fragmentation ion [Ru(dppe)Cp*]+ at m/z 635.
163
The molecular structure of 44 was confirmed by single-crystal X-ray studies on
crystals grown from benzene/hexane. The ORTEP diagram is shown in Figure 55 and
selected bond distances and angles are given in Table 22. The Ru-C(1) bond length of
1.957(1) Å is consistent for a ruthenium carbon single bond. The C(1)-C(2) bond
length of 1.231(2) Å and C(3)-C(4) bond length of 1.212(2) Å confirms they are C≡C
triple bond. The C(2)-C(3) and C(4)-C(41) distances of 1.361(2) Å and 1.416(2) Å
respectively, are consistent with being C-C single bonds. The average length for the
C(n)-F(n) (n = 42 - 46) bond is equal to 1.34(1) Å. The carbon chain is essentially
linear with angles Ru-C(1)-C(2) [171.8(1)o], C(1)-C(2)-C(3) [168.1(1) o], C(2)-C(3)-
C(4) [178.2(1) o] and C(3)-C(4)-C(41) [167.4(1) o]. Similarly, the angle C(44)-
C(441)-N(441) is equal to 178.2(2) o which is nearly linear.
Figure 55: ORTEP view of complex 44 4.3.2.4. Synthesis of Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp*
Two methods were proposed in order to synthesise the complex
Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* (45). The first is the lithiation of
Ru(C≡CC≡CH)(dppe)Cp* with n-BuLi to generate the species
Ru(C≡CC≡CLi)(dppe)Cp*, followed by addition of C6F5OMe (Scheme 102). This is
the previously described lithiation method. From this reaction, 45 was obtained as an
orange powder in 60% yield.
164
C C C CC6F5OMe
Ru
Ph2P PPh2
Li C C C C
F F
OMe
FF
Ru
Ph2P PPh2
C C C CRu
Ph2P PPh2
Li
THF-78oC
C C C C
F F
OMe
FF
Ru
Ph2P PPh2 (45)
Scheme 102: First method for the synthesis of 45
The second method involves the reaction of the previously synthesised complex
Ru(C≡CC≡CC6F5)(dppe)Cp* (42) with sodium methoxide at room temperature. The
fluorine atom in the para position is replaced by an OMe group to give the desired
complex 45 (Scheme 103). The yield of this reaction is higher with 45 being obtained
in 87% yield.
NaOMeC C C C
F F
OMe
FF
Ru
Ph2P PPh2
C C C C
F F
F
FF
Ru
Ph2P PPh2 (45)(42)
Scheme 103: Second method for the synthesis of 45
The 1H and 13C NMR spectra of 45 contained all the typical resonances for the
Ru(dppe)Cp* group. The OMe group gives a singlet at δ 3.30 in the 1H NMR
spectrum and at δ 74.00 in the 13C NMR spectrum. Two resonances were present in
the 19F NMR spectrum as two multiplets at δ -142.07 – -142.18 and -161.51 – -161.62
which is expected due to the 1,4-substitution. This is also a AA’XX’ spin system.
In the infrared spectrum, one ν(CO) band at 1711 cm-1 was observed and two ν(C-F)
bands at 1377 and 1263 cm-1. The ν(CO) band is at a higher frequency in comparison
to an ordinary organic ether linkage. Finally, the ES-MS contains [M + Na]+ at m/z
885, the molecular ion [M]+ at m/z 862 and the fragmentation ion [Ru(dppe)Cp*]+ at
m/z 635.
Crystals of 45 were grown from a CH2Cl2/hexane mixture and the molecular structure
was determined by single-crystal X-ray diffraction studies. The ORTEP diagram is
shown in Figure 56 and selected bond distances and angles are given in Table 22. The
165
Ru(dppe)Cp* fragment has the expected geometry, with Ru-P(1) and Ru-P(2) equals
to 2.269(1) Å and 2.281(1) Å, respectively and the Ru-C(Cp*) distances of 2.241(4) -
2.278(4) Å. The Ru-C(1) bond length of 1.991(4) Å is close to the value expected for
a ruthenium carbon single bond (2.01 Å) and the C(1)-C(2) bond length of 1.227(5) Å
and the C(3)-C(4) bond length of 1.206(5) Å confirms the presence of the C≡C triple
bonds. These bonds are alternated with C-C single bonds C(2)-C(3) [1.373(6) Å] and
C(4)-C(41) [1.49(1) Å]. The average length for the C(n)-F(n) (n = 42 - 46) bond is
equal to 1.342(9) Å. The angles Ru-C(1)-C(2) [173.8(3) o], C(1)-C(2)-C(3) [176.1(4) o], C(2)-C(3)-C(4) [179.7(5) o] and C(3)-C(4)-C(141) [175.7(6) o] in 45 are nearly
linear. The presence of the oxygen atom gives a bent angle with C(144)-O(144)-
C(147) equal to 107.2(5) o.
Figure 56: ORTEP view of complex 45
4.3.2.5. Synthesis of Ru(C≡CC≡CC10F7-2)(dppe)Cp*
The reaction of Ru(C≡CC≡CLi)(dppe)Cp* with C10F8 gave the complex
Ru(C≡CC≡CC10F7-2)(dppe)Cp* (46) as an orange powder in 35% yield (Scheme
104).
C C C CRu
Ph2P PPh2
Li C C C CRuPh2P PPh2
F F
F
FFF
F
C C C CRu
Ph2P PPh2
Li
THF-78oC
C C C CRuPh2P PPh2
F F
FF
F
(46)
C10F8
Scheme 104: The synthesis of 46
166
Two ν(C≡C) bands at 2138 and 2008 cm-1 were observed in the infrared spectrum of
complex 46 as well as two ν(C-F) bands at 1263 and 1197 cm-1. The Ru(dppe)Cp*C4
unit was characterised by similar peaks to previous complexes in the 1H, 31P and 13C
NMR spectra. Finally, the ES-MS of complex 46 in MeOH contained [M + MeOH]+
at m/z 969, [M]+ at m/z 937 and [Ru(dppe)Cp*]+ at m/z 635.
In the 19F NMR spectrum, three doublets of triplets are present at δ -147.33 (3JFF = 18
Hz, 4JFF = 65 Hz), -149.28 (3JFF = 18 Hz, 4JFF = 58 Hz) and -153.04 (3JFF = 18 Hz, 4JFF
= 58 Hz) and two triplets at δ -158.97 (3JFF = 20 Hz) and -160.05 (3JFF = 19 Hz). Five
of the seven expected fluorine resonances are present and it is assumed that the other
two are hidden below the peaks at δ -158.97 and -160.05 as the integrals are higher
for these peaks (47 vs 29). The strong deshielding caused by the presence of the
Ru(dppe)Cp* ligand enabled the ortho fluorines to be assigned, and the presence of
two low-field signals indicates that 2-substitution had occurred. A 19F COSY NMR
spectrum of 46 was also obtained and is shown in Figure 57. This spectrum further
enables to assign the fluorine resonances. The peak at δ -147.33 is coupled to -160.05,
-153.04 and -149.28 and the peak at -149.28 is coupled to -158.97, -153.04 and -
147.33. Then, the peak at δ -153.04 is coupled to -158.97, -160.05 and -147.33 and
the peak at -158.97 is coupled to -160.05, -153.04 and -149.28. And, the peak at δ -
160.05 is coupled to -158.97 and -147.33. Those peaks indicate the interaction of the
adjacent fluorine atoms present on the rings. The fluorine in the 1 and 3 positions are
present at δ -160.05, the fluorines in the 4 and 8 positions at δ -158.97, the one in the
5 position is at δ -153.04, the one at the 6 position is at δ -149.28 and the one at the 7
position is at δ -147.33.
167
Figure 57: 19F COSY NMR of complex 46
Single crystals suitable for X-ray studies were grown from toluene/hexane. The
ORTEP plot of compound 46 is shown in Figure 58 and selected bond distances and
angles are given in Table 22. This confirms the substitution on the 2-position.The Ru-
C(1) bond length of 1.976(2) Å is close to the value expected for a ruthenium carbon
single bond (2.01 Å). The C(1)-C(2) bond length is equal to 1.209(3) Å, the C(3)-C(4)
distance of 1.199(3) Å, the C(2)-C(3) distance is 1.373(3) Å, and the C(4)-C(42)
distance is 1.421(3) Å. They are therefore consistent with being C≡C triple bonds and
168
C-C single bonds. The average length for the C(n)-F(n) (n = 41 - 48) bond is equal to
1.337(3) Å. The carbon chain in 46 is essentially linear, the angles C(1)-C(2)-C(3),
C(2)-C(3)-C(4) and C(3)-C(4)-C(42) being 174.3(2) o, 178.2(3) o and 173.5(3) o,
respectively.
Figure 48: ORTEP view of complex 46
From the data summarised in Table 20 there are several interesting comparisons that
can be drawn from the 19F NMR spectra. It can be observed that the addition of the
Ru(dppe)Cp*-C≡CC≡C- moiety has shifted the chemical shifts of the ortho fluorines
(F-2,6) downfield in complexes 42, 43, 44 and 45 compared to the unsubstituted
reagents. For example, the difference in chemical shift between C6F6 and complex 42
is 24 ppm downfield. This was also observed for the complex
Ru(C≡CC6F5)(dppe)Cp*. The chemical shifts of complex 42 are also shifted
downfield compare to Ru(C≡CC6F5)(dppe)Cp*, which can be explained by the
presence of the extra C≡C triple bond in complex 42.
Furthermore, complex 42 has a triplet for the para fluorine atom while in complexes
43, 44 and 45, this fluorine atom has been replaced by various groups. This has
affected the fluorine atoms in meta position (F-3,5) and it can be noted that the
chemical shift is shifted downfield for the different substituents. The smaller
difference in the chemical shift is obtained with the OMe substituent (5 ppm) while
the electron withdrawing groups NO2 and CN gave a larger difference (15 ppm for 43
and 27 for ppm for 44).
169
Complex F-2,6 (δ) F-3,5 (δ) F-4 (δ) [Ref]
C6F6
-164.9 / / This work
C6F5NO2 -150.70 – -
150.86 -162.44 – -163.10
-155.21 (t, 3JFF = 22 Hz, 1F)
This work
C6F5CN -150.57 – -
150.62 -177.07 – -177.10
-166.47 (t, 3JFF = 21 Hz, 1F)
This work
C6F5OMe -144.09 – -
144.15 -150.90 – -150.98
-145.73 (t, 3JFF = 20 Hz, 1F)
This work
Ru(C≡CC6F5)(dppe)Cp* -145.8
(m, 2F) -168.9 (m, 2F)
-169.1 (t, 3JFF = 21 Hz, 1F)
151
42 -141.40 – -
141.46 (m, 2F)
-166.63 – -166.72 (m, 2F)
-161.79 (t, 3JFF = 22 Hz, 1F)
This work
43 -140.26 – -
140.34 (m, 2F)
-151.88 – -151.96 (m, 2F)
/ This work
44 -138.72 – -
138.83 (m, 2F)
-139.68 – -139.79 (m, 2F)
/ This work
45 -142.07 – -
142.18 (m, 2F)
-161.51 – -161.62 (m, 2F)
/ This work
Table 19: 19F NMR data for complexes 42 - 45
170
Complex IR (cm-1) 1H NMR (δ) 13C NMR (δ) 31P NMR (δ) MS (m/z) 42 ν(C≡C) 2151
(m), 2005 (m); ν(C-F) 1376 (m), 1261 (m)
7.42-7.01 (m, 20H, Ph); 2.49-2.44, 1.79-1.73 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*)
134.48-127.75 (m, Ph); 126.48, 99.23, 89.37, 53.27 (s, C1, C2, C3, C4); 93.80 (t, 2J(CP) 2 Hz, C5Me5); 30.11-29.85 (m, CH2CH2); 10.05 (s, C5Me5)
80.8 (s, dppe) 873, [M + Na]+; 635, [Ru(dppe)Cp*]+
43 ν(C≡C) 2126 (m), 1998 (m); ν(NO) 1634 (w); ν(C-F) 1259 (m), 1016 (m)
7.42-7.04 (m, 20H, Ph); 2.40-2.35, 1.83-1.78 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*)
133.77-126.44 (m, Ph); 100.25, 94.40, 89.38, 76.28 (s, C1, C2, C3, C4); 94.26 (t, 2J(CP) 2 Hz, C5Me5); 31.89-30.11 (m, CH2CH2); 10.22 (s, C5Me5)
80.4 (s, dppe) 901, [M + Na]+; 878,
[M]+; 635,
[Ru(dppe)Cp*]+
44 ν(CN) 2214 (m);
ν(C≡C) 2128 (m), 1995 (m); ν(C-F) 1380 (m), 1264 (m)
7.27-7.06 (m, 20H, Ph); 2.53-2.54, 2.01-1.98 (2 x m, 2 x 2H, CH2CH2); 1.53 (s, 15H, Cp*)
133.68-127.63 (m, Ph); 99.39, 94.75, 75.49, 59.48 (s, C1, C2, C3, C4); 94.25 (s, C5Me5); 85.03 (s, CN); 31.95-30.04 (m, CH2CH2); 10.01 (s, C5Me5)
80.2 (s, dppe) 858, [M + H]+; 635,
[Ru(dppe)Cp*]+
45 ν(C≡C) 2149 (m), 2005 (m); ν(CO) 1711 (m); ν(C-F) 1377 (m), 1263 (m)
7.37-7.02 (m, 20H, Ph); 3.30 (s, 3H, C(O)CH3); 2.48-2.41, 1.79-1.74 (2 x m, 2 x 2H, CH2CH2); 1.54 (s, 15H, Cp*)
136.78-127.64 (m, Ph); 100.28, 92.54, 89.95, 53.26 (s, C1, C2, C3, C4); 93.71 (s, C5Me5); 74.00 (s, C(O)CH3); 30.11-29.87 (m, CH2CH2); 10.08 (s, C5Me5)
80.8 (s, dppe) 885, [M + Na]+; 862,
[M]+; 635,
[Ru(dppe)Cp*]+
46 ν(C≡C) 2138 (m), 2008 (m); ν(C-F) 1263 (m), 1197 (m)
7.54-6.89 (m, 20H, Ph); 2.62-2.49, 1.98-1.78 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*)
133.94-127.75 (m, Ph); 126.56, 95.93, 89.49, 75.48 (s, C1, C2, C3, C4); 94.06 (t, 2J(CP) 2 Hz, C5Me5); 30.25-29.59 (m, CH2CH2); 10.17 (s, C5Me5)
80.7 (s, dppe) 969, [M + MeOH]+; 937, [M]+; 635, [Ru(dppe)Cp*]+
Table 20: Spectroscopic data for complexes 42 - 46
171
Complex 42 44 45 46
Bond Distances (Å)
Ru-P(1)
2.281(1) 2.265(6) 2.269(1) 2.268(6) Ru-P(2)
2.270(3) 2.275(9) 2.281(1) 2.282(6) Ru-C(Cp*)
2.180(2) - 2.35(1) 2.229(1) - 2.290(1) 2.241(4) - 2.278(4) 2.232(2) - 2.272(2) (av.)
2.270(1) 2.265(1) 2.257(4) 2.255(2) Ru-C(1)
1.993(8) 1.957(1) 1.991(4) 1.976(2) C(1)-C(2)
1.180(1) 1.231(2) 1.227(5) 1.209(3) C(2)-C(3)
1.390(1) 1.361(2) 1.373(6) 1.373(3) C(3)-C(4)
1.210(1) 1.212(2) 1.206(5) 1.199(3) C(4)-C(41)
1.450(1) 1.416(2) 1.490(1) 1.421(3) C(n)-F(n) (n = 41- 48)
1.330(1) - 1.340(1) 1.340(1) - 1.340(1) 1.289(9) - 1.378(9) 1.314(3) - 1.354(3)
C(n)-F(n) (av.) 1.340(1) 1.340(1) 1.342(9) 1.337(3) Bond Angles (˚)
P(1)-Ru-P(2)
83.2(8) 80.1(3) 83.4(4) 83.3(2) P(1)-Ru-C(1)
83.9(1) 86.0(5) 79.8(1) 80.5(6) P(2)-Ru-C(1)
86.9(3) 85.7(6) 91.2(1) 87.1(6) Ru-C(1)-C(2)
175.1(9) 171.8(1) 173.8(3) 178.7(2) C(1)-C(2)-C(3)
170.5(8) 168.1(1) 176.1(4) 174.3(2) C(2)-C(3)-C(4)
179.2(8) 178.2(1) 179.7(5) 178.2(3) C(3)-C(4)-C(41)
166.4(1) 167.4(1) 175.7(6) 173.5(3)
Table 21: Selected structural data for complexes 42, 44, 45 and 46
172
4.3.2.6. Further reactions with Ru(C≡CC≡CC6F5)(dppe)Cp*
Previously, the reaction between substituted alkynes and vinylidenes was found to occur via
the cycloaddition of the C≡C bond of the alkyne to the C=C of the vinylidene to form
cyclobutenylidene complexes.152 A ruthenium cyclobutenylidene complex was reported from
the reaction of the butatrienylidene [Ru(C=C=C=CH2)(dppe)Cp*]+ with the diynyl
Ru(C≡CC≡CTMS)(dppe)Cp* (Scheme 105).12
C C C CRu
Ph2P PPh2
TMS
CCCC Ru
PPh2Ph2P
H
H +
+
C C CC
Ru
Ph2P PPh2
CCCC
Ru
PPh2Ph2P
H H
TMS
Scheme 105: Proposed mechanism for the formation of the ruthenium cyclobutenylidene
Therefore, the complex Ru(C≡CC≡CC6F5)(dppe)Cp* (42) was treated with HBF4.OEt2 at
room temperature and the cyclobutenylidene complex
[{Cp*(dppe)Ru(C≡C)}2{C4(C6F5)2H}]BF4 (47) was obtained as a bright blue product in 84%
yield. The characteristic peaks for the Ru(dppe)Cp* groups are present in the 1H, 31P and 13C
NMR spectra of complex 47. The 1H NMR spectrum also shows a singlet at δ 2.02 for a
single proton while in the infrared spectrum, one ν(CH) band at 2924 cm-1 and two ν(C-F)
bands at 1264 and 1158 cm-1 were observed. Further characterisation of 47 was obtained from
the ES-MS which contained ions corresponding to [M - H]+ at m/z 1700 and [Ru(dppe)Cp*]+
at m/z 635.
The 19F NMR spectrum obtained shows interesting features due to the asymmetry of the
molecule. The two C6F5 groups are inequivalent and are in different chemical environments.
This gives two multiplets for the meta fluorine atoms at δ -163.73 – -163.61 and -165.19 – -
173
165.26 while two multiplets for the ortho fluorine are present at δ -137.77 – -137.80 and at -
143.77 – -143.64. The para fluorine atoms are assigned to two triplets at δ -156.59 (3JFF = 22
Hz) and -157.33 (3JFF = 22 Hz).
The formation of [(Cp*(dppe)Ru(C≡C)2{C4(C6F5)2H}]BF4 (47) can be explained by the [2 +
2]-cycloaddition of the C≡C triple bond of diynyl 42 with the C=C double bond of
[Ru{C=C=C=C(C6F5)H}(dppe)Cp*]+ probably formed in situ (Scheme 106).
C C C CRu
Ph2P PPh2
C6F5
CCCC Ru
PPh2Ph2P
H
C6F5 +
C C C
C
Ru
Ph2P PPh2
CCC
C
Ru
PPh2Ph2P
H C6F5
C6F5
(47)
+
Scheme 106: Proposed mechanism for the formation of 47
In addition, the complex Ru(C≡CC≡CC6F5)(dppe)Cp* (42) reacts with the electron deficient
alkene TCNE. The cycloaddition of TCNE to one of the C≡C triple bonds is followed by ring-
opening to give Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48) in 97% yield (Scheme
107). It is noteworthy that neither the other isomer nor the bis(adduct) were obtained when an
excess of TCNE was used in the reaction.
174
C C C C
F F
F
FF
Ru
Ph2P PPh2
CH2Cl2
C C C C
F F
F
FF
Ru
Ph2P PPh2
F F
F
FF
Ru
Ph2P PPh2
C C
CNCN
CNNC
CC
NC CN
NC CN
C C C C
F F
F
FF
Ru
Ph2P PPh2
C C C C
F F
F
FF
Ru
Ph2P PPh2
F F
F
FF
Ru
Ph2P PPh2
C C
CNCN
CNNC
CC
NC CN
NC CN
(48)
TCNE
(42)
Intermediate
Scheme 107: Proposed mechanism for the synthesis of complex 48
The IR spectrum of 48 shows one ν(CN) band at 2211 cm-1, one ν(C≡C) band at 1964 cm-1
and two ν(C-F) bands at 1262 and 1196 cm-1. The 1H, 31P and 13C NMR spectra shows the
typical resonances for the Ru(dppe)Cp* unit. The 13C NMR spectrum of 48 shows the four
CN resonances at δ 116.53, 116.33, 111.30 and 110.62. The resonances for the carbon atoms
of the C4 chains were found as four singlets at δ 154.01, 101.00, 92.81 and 78.91. They could
not be assigned to the individual carbons as it could not be determined which triple bond was
attacked by the TCNE. It can only be suggested that the TCNE was added on the C≡C triple
bond adjacent to the fluorine ring due to steric hindrance around the Ru(dppe)Cp* ligand.
In the 19F NMR spectrum two multiplets were present at δ -135.50 – -136.00 and -159.86 – -
160.28 corresponding to the ortho and meta fluorines respectively and a triplet at δ -148.54
(3JFF = 22 Hz) was assigned to the para fluorine. Furthermore, in the ES-MS of 48, ions
corresponding to [M + Na]+ at m/z 1001 and [Ru(dppe)Cp*]+ at m/z 635 were present.
175
F F
F
FF
[Ru*] C C CC
NC CN
NC CN
C C
F F
F
FF
[Ru*] C C
F F
F F
FF
C C LiC C[Ru*]
C C C C[Ru*]
F F
NO2
FFF
F F
CN
FF
C C C C[Ru*]
F F
CN
FF
FF
F
F F
OMe
F
F
F F
NO2
F
C C C C[Ru*]
F F
OMe
FF
C[Ru*] C [Ru*]C CC
CCC
H C6F5
C6F5
+
HBF4
[Ru*] = Ru(dppe)Cp*
TCNE
NaOMe
(44)
(45)
(47)
(42)
(43)
(48)
C C C C[Ru*]
F FF
FFF
F
(46)
F
F
FF
F
F
F F
Figure 59: Summary of polyfluoroaromatic products synthesised
176
4.4. Electrochemistry
4.4.1. CV of products from the reactions with organic reagents
The redox properties of the complexes Ru(C≡CC≡CMe)(dppe)Cp* (33),
Ru{C≡CC≡CC(O)Ph}(dppe)Cp* (34) and Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* (38)
were studied. Their cyclic voltammograms show single fully-reversible processes at
+0.27 V, at +0.25 V and at +0.21 V, respectively. The cyclic voltammogram of 33 is
shown as an example in Figure 60. The cyclic voltammogram of complex
Ru(C≡CC≡CH)(dppe)Cp* shows one single process at + 0.44V.30 Hence, the
oxidation potentials of complexes 33, 34 and 38 are lower than that for
Ru(C≡CC≡CH)(dppe)Cp*. This can be explained by the terminal proton being
replaced by the different end-groups.
Figure 60: Cyclic voltammogram of 33
Complex {Cp*(dppe)Ru(C≡CC≡C)}2(COCO) (37) has a very interesting structure
since it is composed of a C10 carbon chain which contains two CO groups in the
centre. The redox properties of this complex were investigated. In the CV of 37 one
two-electron partially reversible process is observed at +0.31 V (ia/ic = 0.8) and is
diffusion controlled. Another wave is also present and is most likely due to the
unstability of the starting material which could have decompose in the cell (Figure
61). The two electron process was determined by comparing the difference between
177
Ea and Ec for ferrocene, which undergoes a one electron process, to 37. The two-
electron redox process indicates that there is no communication between the two end-
groups, the two rutheniums are oxidised and reduced at the same potential. Thus, the
insertion of the COCO group has broken the π-conjugation and results in a loss of
electronic interaction between the ruthenium termini.
Figure 61: Cyclic voltammogram of 37
4.4.2. CV of products from the reactions with polyfluoroaromatic reagents
The redox properties of complexes Ru(C≡CC≡CC6F5)(dppe)Cp* (42),
Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* (44) and Ru(C≡CC≡CC10F7-2)(dppe)Cp* (46)
were studied. Their cyclic voltammograms show single partially reversible processes
at +0.56 V (ia/ic = 0.8), +0.50 V (ia/ic = 0.8), +0.51 V (ia/ic = 0.5), respectively (Figure
62). These processes are diffusion controlled. Comparison of 42, 44 and 46 with
Ru(C≡CC≡CH)(dppe)Cp* shows oxidation events occurring at higher redox
potentials. This can be explained as the proton has been replaced by the electron
withdrawing groups C6F5, C6F4CN and C10F7 in these complexes.
178
Figure 62: Cyclic voltammogram of 42
The cyclic voltammogram of complex Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* (43) was
also acquired. One irreversible process is observed at – 1.45 V and one partially
reversible process is observed at +0.52 V (ia/ic = 0.7) (Figure 63). The wave at –1.45
V is a reduction process while the one at +0.52 V is the oxidation of the Ru(dppe)Cp*
moiety. If the oxidation wave of complex 43 is compared with that of
Ru(C≡CC≡CH)(dppe)Cp*, it can be seen that it occurs at a higher potential, which is
consistent with the presence of the electron withdrawing C6F4NO2 group.
Figure 63: Cyclic voltammogram of 43
179
Furthermore, the cyclic voltammogram of Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* (45)
shows two partially reversible processes at +0.17 V (ia/ic = 0.5) and +0.34 V (ia/ic =
0.4) (Figure 64). These redox processes are diffusion controlled. The first oxidation
wave of complex 45 is at +0.17 V, which is at lower potential than that of
Ru(C≡CC≡CH)(dppe)Cp*. One possible explanation is due to the presence of the
C6F4OMe group which produces a combination of two different effects: the first effect
is the inductive effect of the electron-poor fluorine atoms (electron withdrawing)
while the second effect is the resonance effect of the OMe group (electron donating).
The resonance effect is the most important contributor to the redox potential of
complex 45.
Figure 64: Cyclic voltammogram of 45
Finally, the cyclic voltammogram of the complex
Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48) was obtained. It shows two
partially reversible processes at -0.89 V (ia/ic = 0.7) and -0.52 V (ia/ic = 0.8) which are
diffusion controlled. These correspond to reduction waves usually observed with
TCNE adducts where the electron is delocalised onto the electron-withdrawing CN
group. One fully reversible process is also observed at +0.86 V (ia/ic = 0.9) which
corresponds to the oxidation of the Ru(dppe)Cp* moiety (Figure 65).
180
Figure 65: Cyclic voltammogram of 48 The oxidation potential of complex 48 is higher than the first oxidation potential of
the complex Ru(C≡CC≡CH)(dppe)Cp* and 42 as a consequence of the addition of
TCNE, another electron withdrawing group.
181
4.5. Conclusions
In conclusion, the nucleophilic complex Ru(C≡CC≡CLi)(dppe)Cp* was reacted
successfully with a range of organic reagents to afford new diynyl complexes of
general formula Ru(C≡CC≡CR)(dppe)Cp* where R is an organic group (33 - 38). The
electrochemical studies show that minimal electronic communication between the
terminal end-groups is present in these complexes. The reaction of
Ru(C≡CC≡CLi)(dppe)Cp* with TCNE also afforded three different complexes.
Furthermore, Ru(C≡CC≡CLi)(dppe)Cp* was reacted with polyfluoroaromatic
reagents to afford complexes 42 - 46 in very good yields. Complex
Ru(C≡CC≡CC6F5)(dppe)Cp* (42) was further involved in two reactions: the first gave
the cyclobutenylidene complex [{Cp*(dppe)Ru(C≡C)}2{C4(C6F5)2H}]BF4 (47) while
the reaction with TCNE afforded the complex
Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48).
Therefore, based upon the successful results described in this chapter, the complex
Ru(C≡CC≡CLi)(dppe)Cp* is certain to see increasing use in the preparation of
diverse types of complexes.
182
4.6. Experimental General experimental conditions are detailed on page viii. Reagents: The compounds Ru(C≡CC≡CH)(dppe)Cp*30 was prepared by standard literature
methods. n-BuLi, TCNE, C10F8, HBF4.OEt2 were used as received from Sigma-
Aldrich. MeI, benzoyl chloride, acetyl chloride, methyl chloroformate, oxalyl
chloride, benzaldehyde, C6F6, C6F5NO2, C6F5CN, C6F5OCH3 were freshly distilled
under nitrogen.
Ru(C≡CC≡CMe)(dppe)Cp* (33) A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (5 mL) was
treated with n-BuLi (91 µL, 1.6 M solution in hexane) and stirred for 30 min at -78oC.
An aliquot of MeI (32 µL, 0.51 mmol) was added and the reaction was allowed to
warm to r.t. over 3 h. The solvent was then removed and the yellow residue extracted
with hexane (60 mL) and filtered via cannula. The solvent was evaporated to dryness
to give Ru(C≡CC≡CMe)(dppe)Cp* (33) as a bright yellow powder (40 mg, 70%).
Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane. Anal.
Calcd. (C41H42P2Ru): C, 70.47; H, 6.06. Found: C, 70.45; H, 5.99. IR (CH2Cl2, cm-1):
ν(C≡C) 2029 (m), 1908 (m). 1H NMR (C6D6): δ 7.28-6.89 (m, 20H, Ph); 2.65-2.62,
2.01-1.87 (2 x m, 2 x 2H, CH2CH2); 1.73 (s, 3H, CH3); 1.60 (s, 15H, Cp*). 13C NMR
(C6D6): δ 133.96-127.42 (m, Ph); 124.69, 91.73, 76.86, 52.46 (s, C1, C2, C3, C4);
93.25 (s, C5Me5); 29.88-29.27 (m, CH2CH2); 21.03 (s, CH3); 10.12 (s, C5Me5). 31P
NMR (C6D6): δ 81.6 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 731, [M + MeOH]+;
635, [Ru(dppe)Cp*]+.
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Ru{C≡CC≡CC(O)Ph}(dppe)Cp* (34)
Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) with benzoyl
chloride (17 µL, 0.14 mmol) gave Ru{C≡CC≡CC(O)Ph}(dppe)Cp* (34) as a red
powder (43 mg, 75%). Anal. Calcd. (C47H44P2ORu): C, 71.65; H, 5.63. Found: C,
71.76; H, 5.60. IR (Nujol, cm-1): ν(C≡C) 2109 (m), 2000 (m); ν(CO) 1716 (m). 1H
NMR (C6D6): δ 7.28-7.05 (m, 25H, Ph); 2.54-2.50, 2.18-2.08 (2 x m, 2 x 2H,
CH2CH2); 1.51 (s, 15H, Cp*). 13C NMR (C6D6): δ 206.41 (s, CO); 133.63-127.63 (m,
Ph); 112.17, 101.00, 95.59, 63.08 (s, C1, C2, C3, C4); 94.13 (t, 2J(CP) 2 Hz, C5Me5);
30.12-29.23 (m, CH2CH2); 10.02 (s, C5Me5). 31P NMR (C6D6): δ 80.5 (s, dppe). ES-
MS (+ve ion, MeOH, m/z): 811, [M + Na]+; 788, [M]+; 635, [Ru(dppe)Cp*]+.
Ru{C≡CC≡CC(O)Me}(dppe)Cp* (35)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (2.5 mL) was
treated with n-BuLi (64 µL, 2.3 M solution in hexane) and stirred for 30 min at -78oC.
Acetyl chloride (26 µL, 0.36 mmol) was added, the reaction was stirred at -78oC for 1
h and then allowed to warm to r.t. over 1 h. Hexane (20 mL) was added dropwise to
the rapidly stirred solution and a precipitate was filtered to give
Ru{C≡CC≡CC(O)Me}(dppe)Cp* (35) as a bright yellow crystalline powder (34 mg,
60%). Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane.
Anal. Calcd. (C42H42P2ORu): C, 69.40; H, 5.83. Found: C, 69.36; H, 5.92. IR (Nujol,
cm-1): ν(C≡C) 2048 (m), 2004 (m); ν(CO) 1710 (m). 1H NMR (C6D6): δ 7.23-7.02
(m, 20H, Ph); 2.68-2.61, 1.85-1.78 (2 x m, 2 x 2H, CH2CH2); 2.14 (s, 3H, C(O)CH3);
1.58 (s, 15H, Cp*). 13C NMR (C6D6): δ 201.57 (s, CO); 134.51-126.96 (m, Ph);
121.86, 119.52, 102.13, 90.15 (s, C1, C2, C3, C4); 94.38 (s, C5Me5); 33.35 (s,
C(O)CH3); 30.83-30.13 (m, CH2CH2); 10.83 (s, C5Me5). 31P NMR (C6D6): δ 81.7 (s,
dppe). ES-MS (+ve ion, MeOH, m/z): 725, [M]+; 635, [Ru(dppe)Cp*]+.
184
Ru{C≡CC≡CC(O)OMe}(dppe)Cp* (36)
Similarly, from Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.07 mmol) and methyl
chloroformate (12 µL, 0.15 mmol) was obtained Ru{C≡CC≡CC(O)OMe}(dppe)Cp*
(36) as a yellow powder (20 mg, 40%). IR (Nujol, cm-1): ν(C≡C) 2008 (m), 1971 (m);
ν(CO) 1723 (m). 1H NMR (C6D6): δ 7.26-7.02 (m, 20H, Ph); 2.43-2.38, 2.13-2.06 (2
x m, 2 x 2H, CH2CH2); 1.68 (s, 3H, C(O)CH3); 1.53 (s, 15H, Cp*). 31P NMR (C6D6):
δ 80.6 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 743, [M]+; 635, [Ru(dppe)Cp*]+.
{Cp*(dppe)Ru(C≡CC≡C)}2(COCO) (37)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (5 mL) was
treated with n-BuLi (91 µL, 1.6 M solution in hexane) and stirred for 30 min at -78oC.
An aliquot of oxalyl chloride (3 µL, 0.03 mmol) was added and the reaction was
allowed to warm to r.t. over 3 h. The solvent was then evaporated to only few mls and
hexane (30 mL) was added dropwise to the rapidly stirred solution and a precipitate
was filtered to give {Cp*(dppe)Ru(C≡CC≡C)}2(COCO) (37) as an orange powder (23
mg, 55%). Anal. Calcd. (C82H78O2P4Ru2): C, 69.28; H, 5.53. Found: C, 69.57; H,
5.09. IR (CH2Cl2, cm-1): ν(C≡C) 2095 (m), 1999 (m); ν(CO) 1655 (m). 1H NMR
(C6D6): δ 7.99-6.89 (m, 24H, Ph); 2.20-2.14, 2.02-1.91 (2 x m, 2 x 2H, CH2CH2);
1.59 (s, 15H, Cp*). 13C NMR (C6D6): δ 213.74 (s, CO); 133.80-127.61 (m, Ph);
123.62, 100.28, 69.53, 55.62 (s, C1, C2, C3, C4); 90.62 (s, C5Me5); 30.01-29.75 (m,
CH2CH2); 9.94 (s, C5Me5). 31P NMR (C6D6): δ 80.1 (s, dppe). ES-MS (+ve ion,
MeOH, m/z): 1453, [M + MeOH]+; 635, [Ru(dppe)Cp*]+.
Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* (38)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (5 mL) was
treated with n-BuLi (91 µL, 1.6 M solution in hexane) and stirred for 30 min at -78oC.
Benzaldehyde (15 µL, 0.14 mmol) was added and the solution was stirred for 30 min.
185
The solution was then quenched with water and allowed to warm to r.t. over 2 h.
Solvent was removed to give an orange residue which was then dissolved in hexane
(60 mL) and the solution was filtered via cannula and evaporated to dryness to give
Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* (38) as a bright orange crystalline powder (44
mg, 76%). Anal. Calcd. (C47H46P2ORu): C, 71.37; H, 5.87. Found: C, 70.92; H, 5.87.
IR (Nujol, cm-1): ν(OH) 3303 (w); ν(C≡C) 2106 (m), 2000 (m). 1H NMR (C6D6): δ
7.29-7.03 (m, 25H, Ph); 5.52 (s, 1H, OH); 2.58-2.56, 1.80-1.74 (2 x m, 2 x 2H,
CH2CH2); 1.66 (s, 1H, CH); 1.57 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.74-127.68
(m, Ph); 122.10, 99.22, 88.72, 65.85 (s, C1, C2, C3, C4); 93.24 (s, br, C5Me5); 79.89 (s,
C(H)PhOH); 29.90-29.29 (m, CH2CH2); 10.07 (s, C5Me5). 31P NMR (C6D6): δ 81.3 (s,
dppe). ES-MS (+ve ion, MeOH, m/z): 813, [M + Na]+; 790, [M]+; 635,
[Ru(dppe)Cp*]+.
{Ru(dppe)Cp*}2{µ-C≡CC[=C(CN)2]C[=C(CN)2]C≡C} (39)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (5 mL) was
treated with n-BuLi (70 µL, 1.5 M solution in hexane) and stirred for 30 min at -78oC.
TCNE (9 mg, 0.07 mmol) was added and the reaction was stirred at -78oC for 30 min
and then at r.t. for 4 h. The solvent was removed and the residue was dissolved in
minimum amount of CH2Cl2 and purified by preparative TLC, eluted with CH2Cl2 to
afford a red product as {Ru(dppe)Cp*}2{µ-C≡CC[=C(CN)2]C[=C(CN)2]C≡C} (39)
(Rf 0.33) (35 mg, 32%). Anal. Calcd. (C84H78N4P4Ru2): C, 68.65; H, 5.35; N, 3.81.
Found: C, 68.71; H, 5.79; N, 3.72. IR (CH2Cl2, cm-1): ν(CN) 2208 (w), 2075 (w);
ν(C≡C) 1967 (sh), 1866 (m). 1H NMR (CDCl3): δ 7.33-6.92 (m, 40H, Ph); 2.34-2.26,
2.18-2.14 (2 x m, 2 x 4H, CH2CH2); 1.58 (s, 30H, Cp*). 31P NMR (CDCl3): δ 81.3 (d, 3J(PP) 13 Hz, dppe), 79.9 (d, 3J(PP) 13 Hz, dppe). ES-MS (m/z): 1493 [M + Na]+;
635, [Ru(dppe)Cp*]+. Literature IR: ν(CN) 2208 (w), 2193 (w); ν(C≡C) 1973 (sh),
1959 (m). 1H NMR: δ 7.71-6.77 (m, 40H, Ph); 2.44, 1.98 (2 x m, 2 x 4H, CH2CH2);
1.51 (t, 4J(HP) 2 Hz, 30H, Cp*). 31P NMR: δ 79.9 (d, 3J(PP) 13 Hz, dppe), 76.0 (d, 3J(PP) 13 Hz, dppe). ES-MS (m/z): 1493 [M + Na]+.12
186
Ru{C≡CC3NH(CN)(CO)=C(CN)2}(dppe)Cp* (40)
From the same reaction, a second blue band was collected to afford
Ru{C≡CC3NH(CN)(CO)=C(CN)2}(dppe)Cp* (40) (Rf 0.27) (10 mg, 20%). Single
crystals suitable for X-ray studies were grown from CH2Cl2/hexane. Anal. Calcd.
(C46H40N4OP2Ru): C, 66.65; H, 4.87; N, 6.76. Found: C, 66.54; H, 5.44; N, 6.44. IR
(CH2Cl2, cm-1): ν(NH) 3058 (w); ν(CN) 2212 (w); ν(C≡C) 1954 (m); ν(CO) 1716
(m); ν(C=C) 1603 (w). 1H NMR (CDCl3): δ 7.62-7.23 (m, 20H, Ph); 2.74-2.68, 1.83-
1.76 (2 x m, 2 x 2H, CH2CH2); 1.68 (s, 15H, Cp*). 31P NMR (CDCl3): δ 72.9 (s,
dppe). ES-MS (+ve ion, MeOH, m/z): 659, [Ru(dppe)Cp*C2]+ ; 635, [Ru(dppe)Cp*]+.
High resolution MS (m/z): 851.1624, [M + Na]+.
Ru{C≡CC4N(NH)H(Me)C(CN)2)}(dppe)Cp* (41)
From the same reaction, a third band was collected to afford a bright orange product
Ru{C≡CC4N(NH)H(Me)C(CN)2)}(dppe)Cp* (41) (Rf 0.23) (8 mg, 16%). Single
crystals suitable for X-ray studies were grown from CH2Cl2/hexane. IR (CH2Cl2, cm-
1): ν(CH) 2926 (m); ν(CN) 2204 (m); ν(C≡C) 2024 (m); ν(C=C) 1644 (w); ν(NH)
1529 (w). 1H NMR (CDCl3): δ 7.07-7.63 (m, 20H, Ph); 2.31-2.27, 2.18-2.13 (2 x m, 2
x 2H, CH2CH2); 4.19 (s, H, NH); 2.17 (s, 3H, CH3); 1.54 (s, 15H, Cp*); 1.26 (s, H,
CH). 31P NMR (CDCl3): δ 79.7 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 816, [M]+ ;
635, [Ru(dppe)Cp*]+. High resolution MS (m/z): 817.211, [M + H]+.
Ru(C≡CC≡CC6F5)(dppe)Cp* (42)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (10 mL) was
treated with n-BuLi (91 µL, 1.6 M solution in hexane) and stirred at -78oC for 30 min.
C6F6 (17 µL, 0.14 mmol) was then added and the reaction was stirred at -78oC for 1 h
before being allowed to warm to r.t. over 3 h. Solvent was then removed to give a
residue which was then dissolved in hexane (90 mL) and the solution was filtered via
187
cannula and evaporated to dryness to give Ru(C≡CC≡CC6F5)(dppe)Cp* (42) as an
orange crystalline powder (50 mg, 80%). Single crystals suitable for X-ray studies
were grown from CH2Cl2/hexane. Anal. Calcd. (C46H39F5P2Ru): C, 64.93; H, 4.62.
Found: C, 64.72; H, 4.90. IR (Neat, cm-1): ν(C≡C) 2151 (m), 2005 (m); ν(C-F) 1376
(m), 1261 (m). 1H NMR (C6D6): δ 7.42-7.01 (m, 20H, Ph); 2.49-2.44, 1.79-1.73 (2 x
m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ 134.48-127.75 (m, Ph);
126.48, 99.23, 89.37, 53.27 (s, C1, C2, C3, C4); 93.80 (t, 2J(CP) 2 Hz, C5Me5); 30.11-
29.85 (m, CH2CH2); 10.05 (s, C5Me5). 19F NMR (C6D6): δ -141.40 – -141.46 (m, 2F,
o-F); -161.79 (t, 3JFF = 22 Hz, 1F, p-F); -166.63 – -166.72 (m, 2F, m-F). 31P NMR
(C6D6): δ 80.8 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 873, [M + Na]+; 635,
[Ru(dppe)Cp*]+.
Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* (43)
Similarly, from Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) and C6F5NO2 (30 µL,
0.14 mmol) was obtained Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* (43) as a purple powder
(52 mg, 80%). Anal. Calcd. (C46H39F4NO2P2Ru): C, 63.01; H, 4.48; N, 1.60. Found:
C, 63.07; H, 4.52, N, 1.63. IR (Neat, cm-1): ν(C≡C) 2126 (m), 1998 (m); ν(NO) 1634
(w); ν(C-F) 1259 (m), 1016 (m). 1H NMR (C6D6): δ 7.42-7.04 (m, 20H, Ph); 2.40-
2.35, 1.83-1.78 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ
133.77-126.44 (m, Ph); 100.25, 94.40, 89.38, 76.28 (s, C1, C2, C3, C4); 94.26 (t, 2J(CP) 2 Hz, C5Me5); 31.89-30.11 (m, CH2CH2); 10.22 (s, C5Me5). 19F NMR (C6D6): δ
-140.26 – -140.34 (m, 2F); -151.88 – -151.96 (m, 2F). 31P NMR (C6D6): δ 80.4 (s,
dppe). ES-MS (+ve ion, MeOH, m/z): 901, [M + Na]+; 878, [M]+; 635,
[Ru(dppe)Cp*]+.
Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* (44)
Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) with n-BuLi
(0.17 mL, 0.86 M solution in hexane) and C6F5CN (19 µL, 0.14 mmol) gave
188
Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* (44) as a bright orange powder (58 mg, 90%).
Single crystals suitable for X-ray studies were grown from benzene/hexane. Anal.
Calcd. (C47H39F4NP2Ru): C, 65.80; H, 4.59; N, 1.63 Found: C, 65.70; H, 4.61, N,
1.63. (Neat, cm-1): ν(CN) 2214 (m); ν(C≡C) 2128 (m), 1995 (m); ν(C-F) 1380 (m),
1264 (m). 1H NMR (C6D6): δ 7.27-7.06 (m, 20H, Ph); 2.53-2.54, 2.01-1.98 (2 x m, 2
x 2H, CH2CH2); 1.53 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.68-127.63 (m, Ph);
99.39, 94.75, 75.49, 59.48 (s, C1, C2, C3, C4); 94.25 (s, C5Me5); 111.21 (s, CN);
31.95-30.04 (m, CH2CH2); 10.01 (s, C5Me5). 19F NMR (C6D6): δ -138.72 – -138.83
(m, 2F); -139.68 – -139.79 (m, 2F). 31P NMR (C6D6): δ 80.2 (s, dppe). ES-MS (+ve
ion, MeOH, m/z): 858, [M + H]+; 635, [Ru(dppe)Cp*]+.
Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* (45)
1st method:
Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) with n-BuLi
(91 µL, 1.6 M solution in hexane) and C6F5OCH3 (21 µL, 0.14 mmol) afforded
Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* (45) as an orange powder (38 mg, 60%).
2nd method:
Ru(C≡CC≡CC6F5)(dppe)Cp* (42) (31 mg, 0.04 mmol) was dissolved in thf (10 mL)
and NaOMe (1.2 mg Na in 2 mL of MeOH, 0.05 mmol) was added. The solution was
stirred at r.t. for 16 h. The solvent was removed and the residue was dissolved in
hexane (60 mL) and then evaporated to dryness to afford Ru(C≡CC≡CC6F4OMe-
4)(dppe)Cp* (45) as an orange powder (27 mg, 87%). Single crystals suitable for X-
ray studies were grown from CH2Cl2/hexane. Anal. Calcd. (C47H42F4OP2Ru): C,
65.42; H, 4.91. Found: C, 65.39; H, 5.03. IR (Neat, cm-1): ν(C≡C) 2149 (m), 2005
(m); ν(CO) 1711 (m); ν(C-F) 1377 (m), 1263 (m). 1H NMR (C6D6): δ 7.37-7.02 (m,
20H, Ph); 3.30 (s, 3H, OCH3); 2.48-2.41, 1.79-1.74 (2 x m, 2 x 2H, CH2CH2); 1.54 (s,
15H, Cp*). 13C NMR (C6D6): δ 136.78-127.64 (m, Ph); 100.28, 92.54, 89.95, 53.26
189
(s, C1, C2, C3, C4); 93.71 (s, C5Me5); 74.00 (s, OCH3); 30.11-29.87 (m, CH2CH2);
10.08 (s, C5Me5). 19F NMR (C6D6): δ -142.07 – -142.18 (m, 2F); -161.51 – -161.62
(m, 2F). 31P NMR (C6D6): δ 80.8 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 885, [M +
Na]+; 862, [M]+; 635, [Ru(dppe)Cp*]+.
Ru(C≡CC≡CC10F7-2)(dppe)Cp* (46)
Similarly to complex 44, from Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) and
C10F8 (22 mg, 0.07 mmol) was obtained Ru(C≡CC≡CC10F7-2)(dppe)Cp* (46) as an
orange powder (24 mg, 35%). Single crystals suitable for X-ray studies were grown
from toluene/hexane. Anal. Calcd. (C50H39F7P2Ru): C, 64.17; H, 4.20. Found: C,
64.19; H, 4.19. IR (Neat, cm-1): ν(C≡C) 2138 (m), 2008 (m); ν(C-F) 1263 (m), 1197
(m). 1H NMR (C6D6): δ 7.54-6.89 (m, 20H, Ph); 2.62-2.49, 1.98-1.78 (2 x m, 2 x 2H,
CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.94-127.75 (m, Ph); 126.56,
95.93, 89.49, 75.48 (s, C1, C2, C3, C4); 94.06 (t, 2J(CP) 2 Hz, C5Me5); 30.25-29.59 (m,
CH2CH2); 10.17 (s, C5Me5). 19F NMR (C6D6): δ -147.33 (dt, 3JFF = 18 Hz, 4JFF = 65
Hz, 1F); -149.28 (dt, 3JFF = 18 Hz, 4JFF = 58 Hz, 1F); -153.04 (dt, 3JFF = 18 Hz, 4JFF =
58 Hz, 1F); -158.97 (t, 3JFF = 20 Hz, 2F); -160.05 (t, 3JFF = 19 Hz, 2F). 31P NMR
(C6D6): δ 80.7 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 969, [M + MeOH]+; 937,
[M]+; 635, [Ru(dppe)Cp*]+.
[{Cp*(dppe)Ru(C≡C)2}{C4(C6F5)2H}]BF4 (47)
To a solution of Ru(C≡CC≡CC6F5)(dppe)Cp* (42) (31 mg, 0.04 mmol) in THF (15
mL) was added HBF4.O(CH2CH3)2 (6 µL, 0.04 mmol) and the reaction was stirred at
r.t. for 16 h. The solvent was removed and the blue residue was dissolved in minimum
amount of CH2Cl2 and was added to a rapidly stirred hexane solution (40 mL). A
precipitate was collected on a sintered funnel and washed with hexane to afford
[{Cp*(dppe)Ru(C≡C)2}{C4(C6F5)2H}]BF4 (47) as a bright blue powder (23 mg, 84%).
Single crystals suitable for X-ray studies were grown from CHCl3/Et2O. Anal. Calcd.
(C92H79BF14P4Ru2): C, 61.73; H, 4.45. Found: C, 61.50; H, 4.38. IR (Neat, cm-1):
190
ν(CH) 2924 (m), ν(C≡C) 1965 (m), 1897 (m); ν(C-F) 1264 (m), 1158 (m). 1H NMR
(C6D6): δ 7.42-6.89 (m, 20H, Ph); 2.14-2.11, 1.89-1.75 (2 x m, 2 x 2H, CH2CH2);
2.02 (s, 1H, H); 1.70 (s, 15H, Cp*). 13C NMR (CDCl3): δ 320.72, 201.55, 116.7,
102.07, 99.32 (s, C1, C2, C3, C4, C5); 132.59-127.36 (m, Ph); 97.77 (s, C5Me5); 30.01-
29.37 (m, CH2CH2); 9.27 (s, C5Me5). 19F NMR (CDCl3): δ -137.77 – -137.80 (m, 2F,
o-F); -143.77 – -143.64 (m, 2F, o-F); -156.59 (t, 3JFF = 22 Hz, 1F, p-F); -157.33 (t, 3JFF = 22 Hz, 1F, p-F); -163.73 – -163.61 (m, 2F, m-F); -165.19 – -165.26 (m, 2F, m-
F). 31P NMR (C6D6): δ 81.0 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 1700, [M - H]+;
635, [Ru(dppe)Cp*]+.
Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48)
To a suspension of Ru(C≡CC≡CC6F5)(dppe)Cp* (42) (31 mg, 0.04 mmol) in benzene
(15 mL) was added TCNE (5 mg, 0.04 mmol) resulting in an immediate colour
change from yellow to green. The mixture was stirred at r.t. for 7 h. The solvent was
removed and the residue was extracted in minimum CH2Cl2 and purified by
preparative TLC plates using 1:1 CH2Cl2/Et2O as eluant to give a green band (Rf 0.54)
identified as Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48) (41 mg, 97%).
Anal. Calcd. (C52H39F5N4P2Ru): C, 63.79; H, 4.02; N, 5.73. Found: C, 63.43; H, 4.51;
N, 5.41. IR (Neat, cm-1): ν(CN) 2211 (m); ν(C≡C) 1964 (m); ν(C-F) 1262 (m), 1196
(m). 1H NMR (CDCl3): δ 7.45-7.15 (m, 20H, Ph); 2.78-2.69, 2.31-2.23 (2 x m, 2 x
2H, CH2CH2); 1.53 (s, 15H, Cp*). 13C NMR (CDCl3): δ 132.88-128.29 (m, Ph);
154.01, 139.14, 92.81, 78.91 (s, C1, C2, C3, C4); 116.53, 116.33 (2 x s, 2 x CN);
111.30, 110.62 (2 x s, 2 x CN); 97.37 (t, 2J(CP) 2 Hz, C5Me5); 29.98-29.63 (m,
CH2CH2); 9.95 (s, C5Me5). 19F NMR (CDCl3): δ -159.86 – -160.28 (m, 2F, m-F); -
148.54 (t, 3JFF = 22 Hz, 1F, p-F); -135.50 – -136.00 (m, 2F, o-F). 31P NMR (CDCl3): δ
81.1 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 1001, [M + Na]+; 635, [Ru(dppe)Cp*]+.
Chapter Five
Some Chemistry Involving Azide
Reagents
192
5.1. Introduction
The molecules produced by living systems on Earth have always fascinated and
inspired synthetic chemists. Following Nature’s lead, they have endeavored to
develop a set of highly reliable and selective reactions for the rapid synthesis of useful
new compounds. One of the most rapidly growing areas of this research is the
approach named “Click Chemistry”. This concept was introduced by Kolb, Finn and
Sharpless in 2001 and it was defined as a new way of categorising organic reactions
that are modular in nature, highly efficient (high yields), mild and stereospecific.153
The required process characteristics involve simple reaction conditions, readily
available starting materials and reagents, the use of no solvent or a solvent that is
benign or easily removed and simple product isolation. In summary, a “Click”
reaction is easy to perform and work up, with a high yield.153 Click Chemistry not
only allows particular materials to be prepared, it also opens up new avenues for
materials in general to be prepared more efficiently. To date, Click Chemistry has
been used in a broad range of applications, including functionalising biological
molecules154 and monolayers,155-157 advance drug discovery,158-160 solubilising carbon
nanotubes,161 synthesising various dendrimers162,163 and polymers.164,165 These
examples illustrate the diverse range of functional groups and conditions that are
tolerated by Click Chemistry and demonstrate its powerful possibilities.
The most well documented Click reaction is the Huisgen 1,3-dipolar cycloaddition of
terminal alkynes with an azide to generate a 1,2,3-triazole. The potential of organic
azides as highly energetic functional groups for synthesising heterocyclic compounds
was highlighted and their dipolar cycloaddition with alkynes was placed among the
top reactions fulfilling the Click criteria.166,167
However, the cycloaddition of azides with terminal acetylenes was first described to
require elevated temperatures for prolonged periods. The cycloaddition was non-
regiospecific with two possible isomers (1,4 and 1,5) being formed (Scheme
108).166,167 Some control of regiospecificity was obtainable as electron-withdrawing
groups on the acetylene favour production of 1,4 products, and electron-withdrawing
groups on the azide favour production of the 1,5 isomer. However, mixtures were
193
obtained and exclusive production of one isomer by cycloaddition proved elusive.168
Thus, this reaction in this form was not suitable for the requirements of a Click
reaction.
N N N
R160 - 120 oC
hours - days
NN
N
R2
R1
+ NN
NR1
R2
+ H R2
1,4 regioisomer 1,5 regioisomer
Scheme 108: The 1,3-cycloaddition of an azide and terminal alkyne to give 1,2,3-triazoles
The turning point for the Huisgen 1,3-dipolar cycloaddition came with the discovery
in 2002 that copper(I) catalysis accelerates the reaction of azides with terminal
alkynes and also promotes the regiospecificity with exclusive production of the 1,4-
triazole isomer (Scheme 109).166,167,169 The Cu-catalysed azide-alkyne 1,3-dipolar
cycloaddition (CuAAC) is believed to occur by formation of a three-coordinate
copper(I) acetylide that reacts with an azide coligand, proceeding through a carbenoid
intermediate to yield a C-bound copper(I) triazolate. Protonation at carbon affords the
final 1,2,3 triazole.
N N N
R1
NN
N
R2
R1
+ H R2
Cu catalyst
r.t., min - h
Scheme 109: Copper(I)-mediated cycloaddition to give the 1,4-regioisomer
Since its discovery, the copper-catalysed azide-alkyne 1,3-dipolar cycloaddition has
been established as one of the most reliable means for the covalent assembly of
complex molecules. It has enabled a number of applications in medicinal
chemistry,160,170 materials and surface science167,171,172 and molecular biology.173,174
194
The popularity of this method can be explained by several reasons. First, the reaction
is not significantly affected by the steric and electronic properties of the groups
attached to the azide and alkyne reactive centers. The reaction is unaffected by water
and most organic and inorganic functional groups, thus eliminating the need for
protecting-group chemistry. The rate of the Cu-catalysed process is approximately 107
times that of the uncatalysed version, making the reaction conveniently fast in the
temperature range of 0 to 25oC.167 Furthermore, the 1,2,3-triazole unit that results
from the reaction has several advantageous properties: high chemical stability, an
aromatic character and a good hydrogen-bond accepting ability.
However, it must be noted that the need for azides can be a drawback to the reaction.
Azides are highly energetic materials and potentially explosive. This is particularly so
of low-molecular-weight azides which should be handled with extreme caution.
Furthermore, sodium azide has a similar toxicity to sodium cyanide. Other sources of
risk are the use of metals and halogenated solvents with azides which make the
knowledge of working safely with azides imperative. Furthermore, additional research
has revealed that although the speed of the reaction has improved over non-copper
catalysed cycloaddition, the reaction can appear rather slow with overnight reaction
times at room temperature frequently required. A variant to the method involves the
heating of solutions in order to obtain faster reaction times, but this may not be
suitable when biological conjugation is desired.
One example of the application of the copper-catalysed 1,3-dipolar cycloaddition
involves the reaction of sulfonyl azides with alkynes as shown in Scheme 110.167
Depending on the conditions and reagents, the formation of different products may be
observed. For example, N-sulfonylazides are converted to N-sulfonylamidines when
the reaction is conducted in the presence of amines while, under aqueous conditions,
N-acetylsulfonamides are the major products. However, when the reaction is
performed in chloroform in the presence of 2,6-lutidine, N-sulfonyltriazoles are
obtained in good yields.
195
N N N
R2SO2
NN
N
R1
SO2R2
+
H R1
CuI, CHCl3
12 h, 0oC
R1
NHSO2R2
O
N
R1
R3 R4
NSO2R2
CuI, Pyridine
MeCN, r.t., 16h
R3 NR4
CuI, H2O-CHCl3
12 h, r.t.
2,6-lutidineR1 = Ph, TMS, CO2EtR2 = CH2Ph, CH3R3 = Ph, tBuR4 = Ph, CH3OCH2
Scheme 110: The reaction of sulfonyl azides with alkynes
Further examples involve the copper(I)-catalysed 1,3-dipolar cycloaddition of
terminal alkynes and organic azides to give 1,4-disubstituted 1,2,3 triazoles in very
good yields (Scheme 111).175
N N N
R1
H R2+N
NN
R2
R1CuSO4.5H2O
H2O/ tBuOHr.t., 6 - 12 h
R1 = Ph(CH2)2O(CO); R2 = Ph (92%)R1 = (CO)OH, R2 = (CH2)2OPh (88%)
Scheme 111: Copper(I)-catalysed 1,3-dipolar cycloadditions of terminal alkynes
Recently, an analogous method to the Huisgen dipolar addition of azides and alkynes
has been developed and involves a metal-mediated cycloaddition. One such example
involves the cycloaddition of aryl azides to alkynes in the presence of a {Cp*RuCl}4
catalyst (Scheme 112). It was found that such reactions give higher yields, cleaner
products and shorter reaction times than the copper(I) catalysed reaction. In addition,
the copper(I)-catalysed process produces 1,4-disubstituted 1,2,3 triazoles whereas this
new method allows the formation of 1,5-disubstituted 1,2,3 triazoles.
196
N3+
Cl
N
N
[Cp*RuCl]4
DMFCl N N
NN
N
Scheme 112: Ruthenium-mediated cycloaddition
The [3 + 2]-cycloaddition of (triphenylphosphine)gold(I) azide with terminal alkynes
superficially resembles the copper-catalysed chemistry. The reaction proceeds with
the preformed azide complex to give the organo-gold product (Scheme 113). 176
H R N
NN
R
H
(Ph3P)AuN3 Au(PPh3) +Toluene
r.t.
R = Ph (78%)R = p-C6H5F (74%)
Scheme 113: The reaction of AuN3(PPh3) with terminal alkynes
In a variant of this reaction, triazolato complexes can be generated by cycloaddition of
gold(I) alkynyls to azides. Hence, gold(I) alkynyl complexes react with trimethylsilyl
azide at room temperature in the presence of MeOH to afford new gold complexes in
very good yields (Scheme 114).176
(Ph3P)Au R N
NN
R
H
(Ph3P)AuTMSN3+MeOH
r.t.
R = Ph (71%); p-C6H4F (87%) t-Bu (85%); p-Tol (90%)
Scheme 114: Reaction of gold(I) alkynyl with TMSN3
197
In addition, the synthesis of a ruthenium azide complex was reported in 2003. The
reaction of the chlororuthenium complex RuCl(dppe)Cp with NaN3 in ethanol at
reflux for 4 h gave the ruthenium complex Ru(N3)(dppe)Cp (Scheme 115).177
ClRu
Ph2PPPh2
+ NaN3EtOH
∆N3Ru
Ph2PPPh2
Scheme 115: The synthesis of Ru(N3)(dppe)Cp
This complex was further reacted with alkynes and was shown to undergo
cycloaddition reactions to produce triazolates. The reaction is suggested to proceed by
[3 + 2]-cycloaddition of the C≡C bond to the azido group. Two examples are shown
in Scheme 116. The first involves the reaction of Ru(N3)(dppe)Cp with methyl
propiolate while the second is with dimethyl acetylenedicarboxylate. Both reactions
proceed at room temperature in CH2Cl2 and afford the triazole complexes in very
good yields.177
H CO2CH3
H3CO2C CO2CH3
N
N
N
H
Ru
Ph2P PPh2 CO2CH3
N3Ru
Ph2P PPh2
CH2Cl2, r.t. 8 h
N
N
N
CO2CH3
Ru
Ph2P PPh2 CO2CH3
73%
90%
CH2Cl2, r.t. 8 h
Scheme 116: The synthesis of Ru{N3C2HCO2Me}(dppe)Cp and Ru{N3C2(CO2Me)2}(dppe)Cp
198
Furthermore, in 2004 our group reported that the chlororuthenium complex
RuCl(dppe)Cp* reacts with TMSC≡C(TMS)C=NNHTs in MeOH and in the presence
of KF. After heating at reflux for 3 h, the pyrazole complex
Ru{C3H2NNTs}(dppe)Cp* was obtained (Scheme 117).178
KF / MeOHRu
Ph2P PPh2
NC
C
CN
H
HTs
Ru
Ph2P PPh2
Cl + TMS C C C
N
TsHN
TMS∆
Scheme 117: The synthesis of Ru{C3H2NNTs}(dppe)Cp*
199
5.2. Aim of this work
The primary aim of this work was to react various diynyl ruthenium(II) complexes of
general formula [Ru](C≡CC≡CR) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp; R = H,
TMS, Au(PPh3)) with the three different azide reagents TMSN3, TsN3 and
AuN3(PPh3). It was suggested that a Huisgen 1,3-dipolar cycloaddition of the alkynes
with the azides would take place to generate 1,2,3-triazoles as shown in Scheme 118.
N N NR1
C C
NN
NR1
CCR2 [Ru]+C C C C R2[Ru] C C R2[Ru] CC
NN
NR1
[Ru] = Ru(dppe)Cp*; Ru(PPh3)2CpR1 = TMS, Ts, Au(PPh3)R2 = H, TMS, Au(PPh3)
1,4 regioisomer 1,5 regioisomer
Scheme 118: Expected reaction of diynyl ruthenium(II) complexes with azides
200
5.3. Results and Discussion
5.3.1. Reactions of Ru(C≡CC≡CR)(dppe)Cp* (R = TMS, H, Au(PPh3))
First, the reaction of Ru(C≡CC≡CH)(dppe)Cp* with TMSN3 in THF at room
temperature afforded the complex Ru{C2N3(CN)(CH3)}(dppe)Cp* (49) as a yellow
powder in 37% yield (Scheme 119). This complex was also obtained from the
reaction of Ru(C≡CC≡CTMS)(dppe)Cp* with TMSN3 in a similar yield.
C C C CRu
Ph2P PPh2
RTMSN3
THFCH3
C
Ru
Ph2P PPh2
C
CN
N
N
N
R = H, TMS(49)
Scheme 119: The synthesis of complex 49
Complex 49 was characterised by 1H, 31P and 13C NMR, IR. Solution IR spectroscopy
revealed one ν(C≡N) band at 2218 cm-1 and one ν(C=N) band at 1724 cm-1. The
Ru(dppe)Cp* ligand shows all characteristic peaks in the 1H, 31P and 13C NMR
spectra. The addition of the methyl group is confirmed by the presence of a singlet at
δ 1.46 in the 1H NMR spectrum. In the 13C NMR spectrum, the methyl group gives a
singlet at δ 58.74 while the CN group gives a singlet at δ 113.91. The two carbons of
the ring are assigned to two singlets at δ 147.24 and 135.45. The ES-MS of 49 shows
ions corresponding to [M + H]+ at m/z 743 and at m/z 635 for [Ru(dppe)Cp*]+.
A high resolution mass spectrum of 49 was also obtained. The molecular formula
found was C40H42N4P2RuNa which corresponds to a [M + Na]+ at m/z 765.2112. The
calculated value is 765.1825. This value is consistent with the X-ray structure
obtained, confirming the formulation of complex 49.
201
Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane. The
ORTEP plot of compound 49 is shown in Figure 66 and selected bond distances and
angles are given in Table 23. The Ru(dppe)Cp* fragment has the expected geometry,
with Ru-P(1) and Ru-P(2) equal to 2.290(6) Å and 2.291(6) Å, respectively and the
Ru-C(Cp*) distances of 2.219(2) - 2.246(2) Å. The Ru-N(1) bond length of 2.106(1)
Å is slightly longer than a ruthenium carbon single bond (2.01 Å). The C(31)-N(31)
bond length of 1.149(3) Å is consistent with being a C≡N triple bond. The distances
of N(5)-C(4) [1.336(3) Å] and N(2)-C(3) [1.358(3) Å] are consistent with being N-C
single bond. The N(1)-N(2) bond length [1.321(2) Å] is nearly equal to N(1)-N(5)
[1.358(2) Å]. The angle C(3)-C(31)-N(31) in 49 is 177.4(3) o which is essentially
linear.
Figure 66: ORTEP view of 49
202
Bond distances (Å) Bond Angles (o)
Ru-N(1) 2.106(1) Ru-N(1)-N(5) 122.7(1)
Ru-P(1) 2.290(6) Ru-N(1)-N(2) 124.8(1)
Ru-P(2) 2.291(6) P(1)-Ru-P(2) 83.40(2)
Ru-C(Cp*) 2.219(2) - 2.246(2) P(1)-Ru-N(1) 86.05(5)
Ru-C(Cp*) (av.) 2.235(2) P(2)-Ru-N(1) 87.31(5)
N(1)-N(2) 1.321(2) C(3)-C(31)-N(31) 177.4(3)
N(1)-N(5) 1.358(2)
N(5)-C(4) 1.336(3)
N(2)-C(3) 1.358(3)
C(3)-C(4) 1.385(3)
C(31)-N(31) 1.149(3)
Table 23: Selected bond distances (Å) and angles (o) for complex 49
Structural analysis of complex 49 shows that there is one extra nitrogen, the presence
of a CH3 group and that the Ru(dppe)Cp* ligand is connected to a nitrogen atom. Few
pathways for the formation of 49 can be proposed.
First, it can be assumed that the [3 + 2]-cycloaddition reaction occurred either on the
terminal carbons or on the carbons adjacent to the Ru(dppe)Cp* ligand and gave the
two products shown in Figure 67. From there, either molecule could have undergone
fragmentations of various C-C bond and C-N bonds and rearrangement to give
complex 49. However, at present it is not clear how these processes may have
happened and how the C≡N and CH3 groups were formed.
C C
NN
NTMS
C C R[Ru] CC
NN
NTMS
CCR [Ru]
1,4 regioisomer 1,5 regioisomer Figure 67: First possibility for the formation of 49
203
A second proposal is that the [3 + 2]-cycloaddition reaction did not occur and that
instead the azide group added directly to the Ru(dppe)Cp* moiety followed by a
cleavage of the carbon chain. The carbon atoms C2 and C3 of the chain then re-
attached to the nitrogen atoms (Scheme 120). From this intermediate, it can be
assumed that the CH might undergo reduction to give the CH3 moiety but the source
of the extra nitrogen is not known.
C C C C R[Ru]
[Ru] = Ru(dppe)Cp*R = H, TMS
N N NTMS
[Ru] N N N
TMS
+ C C C C R
CR
C
[Ru]C
CN
N
N
Scheme 120: Second possibility for the formation of 49
A third proposal involves the double addition of TMSN3 to the carbon chain. This
process can either be one addition after the other or the double addition can occur
simultaneously. The intermediate obtained is shown in Scheme 121.
N N NTMS
C C C C R[Ru]
[Ru] = Ru(dppe)Cp*R = H, TMS
NNNTMS
C C R[Ru] CC
NN
NTMS
NN
NTMS
Scheme 121: Third possibility for the formation of 49 From this intermediate, the molecule might undergo rearrangement with breaking of
N-N and N-C bonds. A loss of dinitrogen might also occur and could explain the
presence of the extra nitrogen. This could also explain the presence of the two double
bonds in complex 49. This intermediate also induces the migration of the
Ru(dppe)Cp* group onto one of the nitrogens. A possible non-planar rearrangement
of the molecule can be proposed to allow close proximity of the nitrogen atom and the
Ru(dppe)Cp* group. However, it is not obvious how these fragmentations and
204
rearrangements might occur. In addition, it can be suggested that the CH3 group
comes from the THF used as solvent in both reactions. It must be noted that when the
reaction was done in different solvents such as toluene, benzene and hexane, this
product was not obtained. Furthermore, when the reaction was attempted with two
equivalents of TMSN3, the same product was obtained in a better yield of 45%. This
could indicate that the product is more easily formed in the presence of an excess of
azide reagent.
Furthermore, the reaction of Ru(C≡CC≡CH)(dppe)Cp* with another azide reagent
AuN3(PPh3) was attempted. After stirring at 50oC for 24 h in THF, a yellow powder
was obtained as Ru{C2N3(CH3)H}(dppe)Cp* (50) in 41% yield (Scheme 122). It was
found that if the diyndiyl complex Ru(C≡CC≡C[Au(PPh3)])(dppe)Cp* was treated
with TMSN3 and stirred at room temperature for 48 h, the same product was obtained
in a lower yield of 35%.
AuN3(PPh3)
C C C CRu
Ph2P PPh2
RTMSN3
CH3
H
Ru
Ph2P PPh2
C
CN
N
N
R = H, Au(PPh3) (50)
or
Scheme 122: First method for the synthesis of complex 50
Complex 50 displayed the expected resonances in the NMR analysis, IR and ES-MS.
The characteristic peaks for the Ru(dppe)Cp* ligand are present in the 1H, 31P and 13C
NMR spectra. In the 1H NMR spectrum, two singlets are also present at δ 2.18 and
1.26 for the protons of the CH and the CH3 groups, respectively. In the 13C NMR
spectrum, three singlets are present, at δ 133.7 for C-CH3, at 130.92 for the CH unit
and at 58.63 for the CH3 group. In the infrared spectrum, one band was present at
1712 cm-1 for the ν(C=N) stretch. Finally, the ES-MS of 50 shows a peak for the [M]+
ion at m/z 717 and one fragmentation ion corresponding to [Ru(dppe)Cp*]+ at m/z
635.
205
A high resolution mass spectrum of 50 was also obtained. The molecular formula
found was C39H43N3P2Ru which corresponds to a [M]+ at m/z 717.1967 (calcd.
717.1975), confirming the formulation of complex 50.
It must be noted that complex 50 has a very similar backbone to that of complex 49,
the only difference is the presence of a CH group instead of a C≡N group in 49.
Hence, the mechanism of the reaction for the formation of 50 can be suggested to be
very similar to that for the formation of 49. However, the azide reagents used have
different properties (Au(PPh3) versus TMS) and might induce different chemical
behaviour which can explain the absence of the C≡N group in 50. Furthermore, the
two pathways described for the synthesis of 50 converge and give the same product.
This could imply that the presence of the Au(PPh3) unit has an important role in these
reactions. The reaction was also attempted with two equivalents of AuN3(PPh3)
giving the same product in a better yield of 44%. It could again be suggested that an
excess of azide reagent facilitates the synthesis of complex 50.
In addition, Ru(C≡CC≡CH)(dppe)Cp* reacts in toluene with a third azide reagent
TsN3 to afford the complex Ru{NC[C3N2H(NTs)(Ts)]}(dppe)Cp* (51) as a bright
yellow crystalline powder in 43% yield (Scheme 123).
C C C CRu
Ph2P PPh2
HTsN3
TolueneN C
NN S
N
O
O
CH3
SO
O
CH3
Ru
Ph2P PPh2
(51)
Scheme 123: Synthesis of complex 51
206
This complex was characterised by spectroscopic techniques. A ν(C-H) band at 2977
cm-1, a ν(C≡N) band at 2229 cm-1, a ν(C=N) band at 1703 cm-1 and a ν(SO) band at
1179 cm-1 were observed in the infrared spectrum. The 1H spectrum of 51 contained
all the typical resonances for the aromatic protons, the -CH2CH2- bridge of dppe and
the Cp* ligand. The aromatic protons of the Ts groups were found as a pair of
doublets at δ 7.68 (2J(HH) 8 Hz) and 6.61 (2J(HH) 8 Hz) while the methyl group was
found as a singlet at δ 2.25. The pyrazole ring proton gives a singlet at δ 1.23.
Similarly, the 13C NMR spectrum of 51 has characteristic peaks for the Ru(dppe)Cp*
ligand. The Ts groups are confirmed by the presence of different peaks: four singlets
at δ 145.17, 144.89, 138.84 and 134.87 for C6H4, and a singlet at δ 21.14 for the CH3
group. The three ring carbons were found at δ 116.63, 122.85 and 58.52 but could not
be assigned to individual carbons. The ES-MS of complex 51 contained [M + Na]+ at
m/z 1073, [M + H]+ at m/z 1051, and [Ru(dppe)Cp*]+ at m/z 635.
A high resolution mass spectrum of 51 was also obtained. The molecular formula
found was C54H55N4O4P2RuS2 which corresponds to a [M + H]+ at m/z 1051.224. The
calculated value is 1051.219. The molecular formula is consistent with the X-ray
structure obtained, confirming the formulation of complex 51.
Single crystals suitable for X-ray studies were grown from THF/hexane. The ORTEP
diagram of 51 is shown in Figure 68 and selected bond distances and angles are given
in Table 24. The Ru(dppe)Cp* fragment has the expected geometry, with Ru-P(1) and
Ru-P(2) bond lengths of 2.300(1) Å and 2.305(1) Å, respectively and the Ru-C(Cp*)
distances of 2.206(4) - 2.226(4) Å. The Ru-N(1) bond length of 2.006(3) Å is smaller
than the value obtained previously with complex 49 and is very close to a ruthenium
carbon single bond (2.01 Å). The distances of N(7)-C(3) [1.332(6) Å] and N(6)-C(5)
[1.373(6) Å] are consistent with being N-C single bonds. The C(2)-C(3), C(3)-C(4)
and C(4)-C(5) distance of 1.438(6) Å, 1.426 (6) Å and 1.368(6) Å respectively, are
consistent with the presence of C-C single bonds. The angles Ru-N(1)-C(2)
[173.4(4)o] and N(1)-C(2)-C(3) [179.2(5) o] are nearly linear.
207
Figure 68: ORTEP view of 51
Bond distances (Å) Bond Angles (o)
Ru-N(1) 2.006(3) Ru-N(1)-C(2) 173.4(4)
Ru-P(1) 2.300(1) N(1)-C(2)-C(3) 179.2(5)
Ru-P(2) 2.305(1) P(1)-Ru-P(2) 83.2(4)
Ru-C(Cp*) 2.206(4) - 2.226(4) P(1)-Ru-N(1) 85.1(1)
Ru-C(Cp*) (av.) 2.217(4) P(2)-Ru-N(1) 85.1(1)
N(1)-C(2) 1.147(5) C(4)-C(3)-N(7) 113.9(4)
C(2)-C(3) 1.438(6) N(7)-N(6)-S(6) 116.5(4)
C(3)-C(4) 1.426(6)
C(4)-C(5) 1.368(6)
C(3)-N(7) 1.332(6)
C(5)-N(6) 1.373(6)
N(6)-N(7) 1.340(5)
N(4)-S(4) 1.566(4)
S(4)-O(41) 1.459(3)
Table 24: Selected bond distances (Å) and angles (o) for complex 51
208
The analysis of the structure of 51 shows that two Ts groups are present and hence
indicates that a double addition has occurred. The intermediate shown in Scheme 124
can be proposed and two possible pathways for its formation can be suggested. First
the reaction starts with the addition of the two azides followed by fragmentations and
rearrangements. In the second case, there is a [3 + 2]-cycloaddition of only one azide,
followed by fragmentation and rearrangements. The second azide is then added and
further rearrangements might take place to give complex 51. It must also be noted that
in complex 51, a nitrogen atom is connected between the Ru(dppe)Cp* ligand and a
carbon atom. The mechanistic pathways for the fragmentations and rearrangements of
the intermediate to give complex 51 are not obvious.
N N NTs
C C C C H[Ru]
[Ru] = Ru(dppe)Cp*
NNNTs
C C H[Ru] CC
NN
NTs
NN
NTs
Scheme 124: Proposed first step for the formation of 51 In summary, the reactions of Ru(C≡CC≡CR)(dppe)Cp* (R = H, TMS, Au(PPh3)) with
TMSN3, TsN3 and AuN3(PPh3) generated products with three different structural
features. All the data are summarised in Table 25. Only suggestions can be proposed
on the formation of these complexes. The Click reaction seems to occur as the [3 + 2]-
cycloaddition of the azide(s) onto the alkyne is suggested as a possible first step. But,
it appears that the reaction does not stop at this point suggesting that the intermediates
must be very reactive and undergo further chemistry. This second step is not obvious
and more experiments should be done to try to understand what is happening then.
One suggestion will be the isotopic labeling in order to identify which parts of the
reagents are present in the final products. Labelling of the nitrogen atoms of the azide
reagent might help understand if there is double substitution in the case of complexes
49 and 50. Similarly, the carbon atoms of the carbon chain of
Ru(C≡CC≡CR)(dppe)Cp* can be specifically radiolabelled to determine if the
209
carbons present in the final products 49, 50 and 51 are from this starting material.
Furthermore, in order to understand how the CH3 group is formed in complexes 49
and 50, THF-d8 could also be used as solvent and if deuterium atoms are present on
the carbon, this will indicate that it is formed due to this solvent. If not, this
hypothesis could be refuted. Another method to try to describe the presence of this
group or the H atom on complex 50 will be to do the reaction with
Ru(C≡CC≡CD)(dppe)Cp* as starting material in THF and analyse where the
deuterium atom is present on the final product.
210
Table 25: Spectroscopic data for complexes 49 - 51
Complex IR (cm-1)
1H NMR (δ)
13C NMR (δ)
31P NMR (δ)
ES-MS (m/z)
49 ν(C≡N) 2218 (m) ν(C=N) 1724 (m)
7.47-7.08 (m, 20H, Ph); 2.37-2.31, 2.13-2.11 (2 x m, 2 x 2H, CH2CH2); 1.46 (s, 3H, CH3); 1.26 (s, 15H, Cp*)
133.09-127.60 (m, Ph); 147.24 (s, C-CN); 135.45 (s, C-CH3); 113.91 (s, CN); 91.88 (s, C5Me5); 58.74 (s, CH3); 28.39–28.10 (m, CH2CH2); 9.82 (s, C5Me5)
75.1 (s, dppe) 743, [M+ H]+;
635, [Ru(dppe)Cp*]+
50 ν(C=N) 1712 (m) 7.48-6.87 (m, 20H, Ph); 3.14-3.10, 2.73-2.69 (2 x m, 2 x 2H, CH2CH2); 2.18 (s, H, CH); 1.64 (s, 15H, Cp*); 1.26 (s, 3H, CH3)
134.52-127.62 (m, Ph); 133.7 (s, C-CH3); 130.92 (s, CH); 93.02 (s, C5Me5); 58.63 (s, CH3); 30.10–29.77 (m, CH2CH2); 10.28 (s, C5Me5)
75.0 (s, dppe) 717, [M]+; 635, [Ru(dppe)Cp*]+
51 ν(C-H) 2977 (m) ν(C≡N) 2229 (m) ν(C=N) 1703 (m) ν(SO) 1179 (m)
7.68 (d, 2J(HH) 8 Hz, 2H, C6H4); 7.23-6.95 (m, 20H, Ph); 6.61 (d, 2J(HH) 8 Hz, 2H, C6H4); 2.25 (s, 6H, CH3); 2.04-1.99, 1.89-1.85 (2 x m, 8H, CH2CH2); 1.49 (s, 15H, Cp*); 1.23 (s, H, CH)
145.17, 144.89, 138.84, 134.87 (4 x s, C6H4); 130.39-127.06 (m, Ph); 116.63 (s, C); 122.85 (s, C); 92.27 (s, C5Me5); 58.52 (s, C); 28.77-28.18 (m, CH2CH2); 21.14 (s, CH3); 9.79 (s, C5Me5)
74.3 (s, dppe) 1073, [M + Na]+; 1051, [M + H]+; 635, [Ru(dppe)Cp*]+
211
5.3.2. Reactions of Ru(C≡CC≡CH)(PPh3)2Cp
The complex Ru(C≡CC≡CH)(PPh3)2Cp is easily accessible and it was suggested that
this complex should also react with azide reagents and possibly undergo Click
Chemistry. However, it was also assumed that these reactions could behave as shown
in the previous Section since the only difference is the metal ligand moiety
(Ru(PPh3)2Cp vs Ru(dppe)Cp*). This could help understand how the previous
reactions proceeded.
Therefore, the diynyl complex Ru(C≡CC≡CH)(PPh3)2Cp was reacted with the azide
reagent TMSN3 in THF at room temperature for 72 h to give the complex
Ru(N3)(PPh3)2Cp (52) as a yellow-brown powder in 57% yield. Complex 52 was also
obtained from the reaction of Ru(C≡CC≡CH)(PPh3)2Cp with TsN3 stirred in THF at
room temperature for 72 h in slightly higher yield (60%) (Scheme 125).
THF
TMSN3
N3Ru
Ph3P PPh3
Ru
Ph3P PPh3
C C C C HTsN3
or
(52)
Scheme 125: Two methods for the synthesis of complex 52
Complex 52 was characterised by 1H, 31P and 13C NMR, IR and ES-MS. One ν(N3)
band at 1981 cm-1 was observed in the infrared spectrum. In the 1H NMR spectrum, a
multiplet at δ 7.70-6.79 for the phenyl groups and a singlet at δ 4.26 which
corresponds to the cyclopentadienyl Cp ligand are present. In the 13C NMR spectrum,
one multiplet at δ 134.04-125.97 was assigned to the phenyl groups while the singlet
at δ 86.03 was found for the carbons of the Cp ligand. The 31P NMR spectrum of 52
has one resonance at δ 43.3 assigned to the coordinated phosphorus atoms on the
ruthenium. Further characterisation of 52 was obtained from the ES-MS which
contained ions corresponding to [M]+ at m/z 733, and fragmentation ions at m/z 691
for [Ru(PPh3)2Cp]+ and at m/z 429 for [Ru(PPh3)Cp]+.
212
These results indicate that Ru(C≡CC≡CH)(PPh3)2Cp does not undergo [3 + 2]-
cycloaddition nor enter into the reactions described in Section 5.3.1. A proposed
mechanism for these reactions is shown below. It involves the direct attack of the
azide reagent onto the Ru(PPh3)2Cp moiety and cleavage of the carbon chain. This is
the simplest explanation suggested at this time and it should be noted that the -C≡CC≡CH moiety appears to be easier to cleave than first thought (Scheme 126).
C C C C HRu
Ph3P PPh3 NNNR
R = TMS, Ts
Ru
Ph3P PPh3
N3 + C C C C H
(52)
Scheme 126: Proposed mechanism for the formation of 52
In summary, the reactions of Ru(C≡CC≡CH)(PPh3)2Cp with TMSN3 and TsN3 both
gave the ruthenium complex Ru(N3)(PPh3)2Cp (52). These results differ from the
reactions of Ru(C≡CC≡CH)(dppe)Cp* with TMSN3 and TsN3 and it can be assumed
that the presence of the two different ruthenium metal-ligand moiety (Ru(PPh3)2Cp vs
Ru(dppe)Cp*) is the influential factor for this divergence. In addition, complex 52
shows a similar structure to the ruthenium complex Ru(N3)(dppe)Cp reported by
Chang and co-workers.177
5.3.3. Reactions of Ru(C≡CH)(dppe)Cp*
Following the previous results, the reactions of the complex Ru(C≡CH)(dppe)Cp*
with various azide reagents were also investigated. First, Ru(C≡CH)(dppe)Cp* was
reacted with TMSN3 in toluene at room temperature for 72 h. The complex
Ru(N3)(dppe)Cp* (53) was obtained as a yellow powder in 63% yield. The reaction of
Ru(C≡CH)(dppe)Cp* with TsN3 in THF at room temperature for 48 h gave the same
complex in 65% yield (Scheme 127).
213
TsN3 in THF
C C HRu
Ph2P PPh2
TMSN3 in tolueneRu
Ph2P PPh2
N3
(53)
or
Scheme 127: Two methods for the synthesis of complex 53
The 1H NMR spectrum of 53 contained all characteristic peaks for the Ru(dppe)Cp*
ligand with the aromatic protons found as a multiplet at δ 7.25-7.07, the CH2CH2
bridge in dppe as two multiplets at δ 2.37-2.35 and 1.98-1.85 and the protons of the
Cp* ligand as a singlet at δ 1.53. The 31P NMR spectrum shows one singlet at δ 77.7
assigned to the phosphorus nuclei of the Ru(dppe)Cp* fragment. In the IR spectrum,
one ν(N3) band was present at 2035 cm-1. Finally the ES-MS contains [M + Na]+ at
m/z 700 and [Ru(dppe)Cp*]+ at m/z 635.
It should be pointed out that another member of our group carried out the reaction of
Ru(C≡CH)(dppe)Cp* with AuN3(PPh3) and also obtained complex 53.150 All
spectroscopic data obtained agreed with those reported for 53. Single crystals suitable
for X-ray studies were grown and showed that the azide fragment is composed of
N=N double bonds. The molecule is also bent as the angle Ru-N(1)-N(2) is equal to
122.8(8) o as shown in Figure 69.150
Ru
Ph2P PPh2
N
NN
Figure 69: Representation of 53
214
These reactions gave a similar result to the reaction of Ru(C≡CC≡CH)(PPh3)2Cp with
TMSN3 and TsN3 and indicate that Ru(C≡CH)(dppe)Cp* does not undergo [3 + 2]-
cycloaddition. Complexes 53 and 52 only differ by the ligands on the ruthenium atom,
thus it can expected that they will have a similar structure. They can also be related to
the ruthenium complex Ru(N3)(dppe)Cp.177
Furthermore, these reactions could give an indication of what is happening in the
reactions of Ru(C≡CC≡CR)(dppe)Cp* (R = H, TMS, Au(PPh3)) with azides described
in Section 5.3.1. It is possible that complex 53 is formed in these cases. It has then
undergone further chemistry maybe due to the presence of the by-products in solution
and the complexes 49, 50 and 51 are obtained.
215
5.4. Conclusions
In this chapter, the reactions of diynyl ruthenium(II) complexes
Ru(C≡CC≡CR)(dppe)Cp* (where R = H, TMS, Au(PPh3)) with three readily
available azide reagents (TMSN3, TsN3 and AuN3(PPh3)) afforded three different
products, which were characterised spectroscopically and by X-ray analyses. The
mechanisms of formation of these complexes are not apparent but it was suggested
that a Huisgen 1,3-alkyne-azide cycloaddition could have taken place to generate
1,2,3-triazoles as intermediates which then further react to afford complexes 49, 50
and 51.
In addition, the reactions of the complex Ru(C≡CC≡CH)(PPh3)2Cp with two azides
gave the complex Ru(N3)(PPh3)2Cp (52). A similar product was obtained when
Ru(C≡CH)(dppe)Cp* was reacted with azide reagents, generating Ru(N3)(dppe)Cp*
(53) in a good yield. These complexes only differ by the ruthenium moiety and should
have analogous structures. It was also suggested that they were formed from a similar
mechanism.
216
5.5. Experimental
General experimental conditions are detailed on page viii. Reagents: The compounds Ru(C≡CC≡CH)(dppe)Cp*,30 Ru(C≡CC≡CTMS)(dppe)Cp*,30
Ru(C≡CC≡CH)(PPh3)2Cp,30 AuN3(PPh3),179 Ru(C≡CC≡C[Au(PPh3)])(dppe)Cp*,30
Ru(C≡CH)(dppe)Cp*,47 TsN3,180 were all prepared by standard literature methods.
TMSN3 was used as received from Sigma-Aldrich. Despite several attempts accurate
elemental analyses could not be obtained for complexes 49 - 51 and 53.
Ru{C2N3(CN)(CH3)}(dppe)Cp* (49)
1st method:
A solution of Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.07 mmol) in THF (10 mL) was
treated with TMSN3 (10 µL, 0.07 mmol) and stirred at r.t. for 48 h. The solvent was
then evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow
precipitate formed and was filtered on sintered funnel and washed with hexane to give
Ru{C2N3(CN)(CH3)}(dppe)Cp* (49) as a bright yellow powder (20 mg, 37%).
2nd method:
Similarly, Ru(C≡CC≡CTMS)(dppe)Cp* (51 mg, 0.07 mmol) and TMSN3 (9 µL, 0.07
mmol) gave Ru{C2N3(CN)(CH3)}(dppe)Cp* (49) (21 mg, 38%). IR (CH2Cl2, cm-1):
ν(C≡N) 2218 (m); ν(C=N) 1724 (m). 1H NMR (C6D6): δ 7.47-7.08 (m, 20H, Ph);
2.37-2.31, 2.13-2.11 (2 x m, 2 x 2H, CH2CH2); 1.46 (s, 3H, CH3); 1.26 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.09-127.60 (m, Ph); 147.24 (s, C-CN); 135.45 (s, C-CH3);
113.91 (s, CN); 91.88 (s, C5Me5); 58.74 (s, CH3); 28.39–28.10 (m, CH2CH2); 9.82 (s,
217
C5Me5). 31P NMR (C6D6): δ 75.1 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 743, [M+
H]+; 635, [Ru(dppe)Cp*]+. High resolution MS (m/z): 765.2112, [M + Na]+.
Ru{C2N3(CH3)H}(dppe)Cp* (50)
1st method:
A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (10 mL) was
treated with AuN3(PPh3) (37 mg, 0.07 mmol) and stirred at 50oC for 24 h. The solvent
was then evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow
precipitate formed and was filtered on sintered funnel and washed with hexane to give
Ru{C2N3(CH3)H}(dppe)Cp* (50) as a bright yellow powder (13 mg, 41%).
2nd method:
Complex Ru{C2N3(CH3)H}(dppe)Cp* (50) was also obtained (11 mg, 35%) from a
similar reaction between Ru(C≡CC≡C[Au(PPh3)])(dppe)Cp* (50 mg, 0.04 mmol) and
TMSN3 (5 µL, 0.07 mmol) at r.t. for 48 h. IR (CH2Cl2, cm-1): ν(C=N) 1712 (m). 1H
NMR (C6D6): δ 7.48-6.87 (m, 20H, Ph); 3.14-3.10, 2.73-2.69 (2 x m, 2 x 2H,
CH2CH2); 2.18 (s, 1H, CH); 1.64 (s, 15H, Cp*); 1.26 (s, 3H, CH3). 13C NMR (C6D6):
δ 134.52-127.62 (m, Ph); 133.7 (s, C-CH3); 130.92 (s, CH); 93.02 (s, C5Me5); 58.63
(s, CH3); 30.10–29.77 (m, CH2CH2); 10.28 (s, C5Me5). 31P NMR (C6D6): δ 75.0 (s,
dppe). ES-MS (+ve ion, MeOH, m/z): 717, [M]+; 635, [Ru(dppe)Cp*]+. High
resolution MS (m/z): 717.1967, [M]+.
Ru{NC[C3N2H(NTs)(Ts)]}(dppe)Cp* (51)
A solution of Ru(C≡CC≡CH)(dppe)Cp* (31 mg, 0.05 mmol) in toluene (10 mL) was
treated with TsN3 (28 mg, 0.14 mmol) and stirred at r.t. for 18 h. The solvent was then
evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow precipitate
formed and was filtered on sintered funnel and washed with hexane to give
218
Ru{NC[C3N2H(NTs)(Ts)]}(dppe)Cp* (51) as a bright yellow crystalline powder (33
mg, 43%). Single crystals suitable for X-ray studies were grown from THF/hexane.
IR (CH2Cl2, cm-1): ν(C-H) 2977 (m); ν(C≡N) 2229 (m); ν(C=N) 1703 (m); ν(SO)
1179 (m). 1H NMR (C6D6): δ 7.68 (d, 2J(HH) 8 Hz, 2H, C6H4); 7.23-6.95 (m, 20H,
Ph); 6.61 (d, 2J(HH) 8 Hz, 2H, C6H4); 2.25 (s, 3H, CH3); 2.04-1.99, 1.89-1.85 (2 x m,
2 x 2H, CH2CH2); 1.49 (s, 15H, Cp*); 1.23 (s, 1H, CH). 13C NMR (C6D6): δ 145.17,
144.89, 138.84, 134.87 (4 x s, C6H4); 130.39-127.06 (m, Ph); 116.63 (s, C); 122.85 (s,
C); 92.27 (s, C5Me5); 58.52 (s, C); 28.77-28.18 (m, CH2CH2); 21.14 (s, CH3); 9.79 (s,
C5Me5). 31P NMR (C6D6): δ 74.3 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 1073, [M +
Na]+; 1051, [M + H]+; 635, [Ru(dppe)Cp*]+. High resolution MS (m/z): 1051.224, [M
+ H]+.
Ru(N3)(PPh3)2Cp (52) 1st method:
A solution of Ru(C≡CC≡CH)(PPh3)2Cp (51 mg, 0.07 mmol) in THF (10 mL) was
treated with TMSN3 (9 µL, 0.07 mmol) and stirred at r.t. for 72 h. The solvent was
then evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow-
brown precipitate formed and was filtered on sintered funnel and washed with hexane
to give Ru(N3)(PPh3)2Cp (52) as a yellow-brown powder (29 mg, 57%).
2nd method:
Complex Ru(N3)(PPh3)2Cp (52) was also obtained (31 mg, 60%) from a similar
reaction between Ru(C≡CC≡CH)(PPh3)2Cp (50 mg, 0.07 mmol) and TsN3 (14 mg,
0.07 mmol). IR (CH2Cl2, cm-1): ν(N3) 1981 (m). 1H NMR (CDCl3): δ 7.70-6.79 (m,
30H, Ph); 4.26 (s, 5H, Cp). 13C NMR (CDCl3): δ 134.04-125.97 (m, Ph); 86.03 (s,
C5H5). 31P NMR (CDCl3): δ 43.3 (s, PPh3). ES-MS (+ve ion, MeOH, m/z): 733, [M]+;
691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.
219
Ru(N3)(dppe)Cp* (53)
1st method:
A solution of Ru(C≡CH)(dppe)Cp* (51 mg, 0.08 mmol) in toluene (10 mL) was
treated with TMSN3 (10 µL, 0.08 mmol) and stirred at r.t. for 72 h. The solvent was
then evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow
precipitate formed and was filtered on sintered funnel and washed with hexane to give
Ru(N3)(dppe)Cp* (53) as a yellow powder (37 mg, 63%).
2nd method:
Complex Ru(N3)(dppe)Cp* (53) was also obtained (35 mg, 65%) from a similar
reaction between Ru(C≡CH)(dppe)Cp* (51 mg, 0.08 mmol) and TsN3 (15 mg, 0.08
mmol) in THF (10 mL) at r.t. for 48 h. IR (CH2Cl2, cm-1): ν(N3) 2035 (s). 1H NMR
(C6D6): δ 7.25-7.07 (m, 20H, Ph); 2.37-2.35, 1.98-1.85 (2 x m, 2 x 2H, CH2CH2);
1.53 (s, 30H, Cp*). 31P NMR (C6D6): δ 77.7 (s, dppe). ES-MS (+ve ion, MeOH, m/z):
700, [M+ Na]+; 635, [Ru(dppe)Cp*]+. Literature150 IR (CH2Cl2, cm-1): ν(N3) 2036 (s). 1H NMR (C6D6): δ 7.32-7.05 (m, 20H, Ph); 2.40-2.38, 1.81-1.78 (2 x m, 2 x 2H,
CH2CH2); 1.50 (s, 30H, Cp*). 31P NMR (C6D6): δ 77.7 (s, dppe). ES-MS (+ve ion,
MeOH, m/z): 677, [M]+; 635, [Ru(dppe)Cp*]+.
220
General conclusions
In summary, this thesis describes the development of new methods for the synthesis
of novel diynyl, diyndiyl and bis(diyndiyl) ruthenium(II) complexes which could not
been obtained from previously known methods.
The first method presented allowed the synthesis of novel symmetric and asymmetric
bis(diyndiyl) ruthenium (II) complexes of the general formula {LnM}-C≡CC≡C-
{M”L”p}-C≡CC≡C-{M’L’m}, featuring two butadiyndiyl carbon chains with metal
ligand end-groups linked by either a Ru(dppe)2 moiety or a trinuclear copper(I) or
silver(I) cluster M3(µ-dppm)3 (M = Cu, Ag). These complexes were studied by cyclic
voltammetry which has enabled the electronic interactions between the two metal
termini along the bridge to be evaluated and to examine the effect of insertion of the
different bridging groups. It was found that the insertion of the Ru(dppe)2 moiety
allows electronic interactions between the terminal groups and these interactions were
increased when compared to the straight-chain analogues. When a trinuclear copper(I)
or silver(I) cluster was inserted, electronic communication was still present between
the metal ligand end-groups, but the electronic interactions were found to diminish
compared to straight-chain analogues.
Furthermore, this work looked at the lithiation of two ruthenium(II) diynyl complexes
Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp. The most favorable
conditions for the synthesis of the lithium complexes Ru(C≡CC≡CLi)(dppe)Cp* and
Ru(C≡CC≡CLi)(PPh3)2Cp were determined. The nucleophilic nature of these
complexes made them valuable starting materials for the synthesis of novel diynyl and
diyndiyl ruthenium(II) complexes. Therefore, the generated lithium complexes
[Ru](C≡CC≡CLi) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) were reacted with
metal halides from a range of metal groups and various electrophiles such as organic
substrates or polyfluoroaromatic compounds. This is the first example of the lithiation
of ruthenium(II) diynyl complexes and this new synthetic route has allowed the
synthesis of a wide range of novel diynyl and symmetric or asymmetric ruthenium(II)
diyndiyl complexes.
221
This thesis also describes the reaction of various diynyl ruthenium(II) complexes with
the three different azide reagents TMSN3, TsN3 and AuN3(PPh3). It was suggested
that a Huisgen 1,3-dipolar cycloaddition of the alkynes with the azides will take place
to generate 1,2,3-triazoles. However, the reactions did not proceed as expected giving
a range of products. This Section of the work has never been explored previously and
exposed a very interesting opportunity for further chemistry.
222
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Complexes Index
1. trans-Ru(C4H)(dppe)2
2. trans-Ru{C4[Ru(dppe)Cp*]}2(dppe)2
3. trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2
4. trans-Ru{C4[Ru(PPh3)2Cp]}2(dppe)2
5. trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2
6. trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2
7. trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2
8. trans-Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2
9. trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2
10. trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2
11. trans-Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2
12. trans-Ru{C4[Ru(dppe)Cp]}{C4[Au(PPh3)]}(dppe)2
13. trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2
14. trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2
15. trans-Ru{C4[Au(PPh3)]}2(dppe)2
16. trans-Ru{C5[Co3(µ-dppm)(CO)7]}2(dppe)2
17. Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2
18. [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6]
19. [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4]
20. [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6]
21. [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4]
22. Ru(C≡CC≡CTMS)(dppe)Cp*
23. Ru(C≡CC≡CTMS)(PPh3)2Cp
24. Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp*
25. Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp
26. {Au(C≡CC≡C[Ru(dppe)Cp*])}2(µ-dppm)
27. Ru{C≡CC≡C[PtCl(PPh3)2]}(dppe)Cp*
28. Ru(C≡CC≡CGePh3)(dppe)Cp*
29. Ru(C≡CC≡CSnPh3)(dppe)Cp*
232
30. {Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*}
31. {Cp(Ph3P)2Ru}(C≡CC≡C){Cu(PPh3)}
32. {Cp(Ph3P)2Ru}(C≡CC≡C){Rh(CO)(PPh3)2}
33. Ru(C≡CC≡CMe)(dppe)Cp*
34. Ru{C≡CC≡CC(O)Ph}(dppe)Cp*
35. Ru{C≡CC≡CC(O)Me}(dppe)Cp*
36. Ru{C≡CC≡CC(O)OCH3}(dppe)Cp*
37. {Ru(C≡CC≡C)(dppe)Cp*}2(CO)2
38. Ru{C≡CC≡CCHPh(OH)}(dppe)Cp*
39. {Ru(dppe)Cp*}2{µ-C≡CC[=C(CN)2]C[=C(CN)2]C≡C}
40. Ru{C≡CC3NH(CN)(CO)=C(CN)2}(dppe)Cp*
41. Ru{C≡CC4N(NH)H(Me)=C(CN)2}(dppe)Cp*
42. Ru(C≡CC≡CC6F5)(dppe)Cp*
43. Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp*
44. Ru(C≡CC≡CC6F4CN-4)(dppe)Cp*
45. Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp*
46. Ru(C≡CC≡CC10F7-2)(dppe)Cp*
47. [{Cp*(dppe)Ru(C≡C)2}{C4(C6F5)2H}]BF4
48. Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp*
49. Ru{C2N3(CN)(CH3)}(dppe)Cp*
50. Ru{C2N3(CH3)H}(dppe)Cp*
51. Ru{NC[C3N2H(NTs)(Ts)]}(dppe)Cp*
52. Ru(N3)(PPh3)2Cp
53. Ru(N3)(dppe)Cp*