In Copyright - Non-Commercial Use Permitted Rights ......Kamiyama, Raul Pereira, Dr. Raphaël...

Research Collection

Doctoral Thesis

Investigating new chiral 1,2-disubstituted ferrocenes

Author(s): Ludwig, Peter Eladio

Publication Date: 2013

Permanent Link: https://doi.org/10.3929/ethz-a-010183093

Rights / License: In Copyright - Non-Commercial Use Permitted

This page was generated automatically upon download from the ETH Zurich Research Collection. For moreinformation please consult the Terms of use.

ETH Library

https://doi.org/10.3929/ethz-a-010183093

http://rightsstatements.org/page/InC-NC/1.0/

https://www.research-collection.ethz.ch

https://www.research-collection.ethz.ch/terms-of-use

Diss. ETH No. 21627

Investigating new chiral 1,2-disubstituted ferrocenes

A dissertation submitted to

ETH ZURICH

for the degree of

DOCTOR OF SCIENCES

presented by

PETER ELADIO LUDWIG

Master of Science ETH in Chemistry

born on 5 January, 1984

citizen of Ardez GR and Spain

accepted on the recommendation of

Prof. Dr. Antonio Togni, examiner

Prof. Dr. Christophe Copéret, co-examiner

Zurich 2013

Über den Hügeln

lautlos der rote Milan

flieh seinen Schatten

– Hannes Joss

7th August, 2013

Dedicated to

the memory of

my father

Acknowledgments

I would like to thank the people, who helped and supported me during my Ph.D. studies:

First of all I thank Professor Antonio Togni for letting me join his group and supervising

me during my thesis, for always having an open door, for the freedom he granted in realising

my own ideas, as well as for his support during my master thesis at Imperial College.

I thank Professor Christophe Copéret for the co-examination of this thesis and helpful

comments.

Special thanks go to Dr. Jan Welch for all the good advice while writing this thesis, and

for the proof–reading, also to Danny Rafaniello for designing the cover.

Also, I want to thank all of the students that I supervised during my thesis, including

Daniel Bachmann who did his master thesis with me, my semester students Johannes Boshkow,

Lucia Meier and Patrick Stücheli, and Luciano Mastrobuoni and Manuela Meister, who both

were my SiROP students.

Furthermore, for technical support during my research I would like to thank the fol-

lowing people: Oliver Sala for the DFT–calculations. Dr. Heinz Rüegger, Dr. Aitor Moreno,

Dr. René Verel and especially Barbara Czarniecki for NMR support. I also want to thank our

crystallography team, first of all my ’Hof–Kristallographen’ Dr. Rino Schwenk and Lukas Sigrist,

as well as the rest of the team: Dr. Raphael Aardoom, Dr. Katrin Niedermann, Dr. Michael Wörle

and Elli Otth.

I want to thank Professor Antonio Mezzetti, Dr. Pietro Butti, Dr. Jonas Bürgler, Dr. Michelle

Flückiger, Dr. Raffael Koller, Dr. Kyrill Stanek and Dr. Jan Welch for all their good advice at

the beginning of and throughout my thesis. In addition I thank all the current and former

members of the Togni and the Mezzetti group for all the fruitful discussions and the good

times together. I especially thank all my labmates from H230 over the years of whom I

would like to particularly mention Dr. Ján Cvengroš, Barbara Czarniecki, Rima Drissi, Takuya

Kamiyama, Raul Pereira, Dr. Raphaël Rochat, Dr. Amata Schira, Dr. Rino Schwenk, Lukas Sigrist

and of course once more my long–time table neighbour Dr. Jan Welch. For all the support,

hanging–out, cheering up and great activities outside of the lab I want to thank Dr. Raphael

Aardoom, Barbara Czarniecki, Rima Drissi, Dr. Michelle Flückiger, Alex Lauber, Dr. Esteban

Mejía, Dr. Katrin Niedermann, Dr. Tina Osswald, Dr. Raphaël Rochat, Dr. Nico Santschi, Dr. Rino

i

Schwenk, Remo Senn and Lukas Sigrist. Moreover, I would like to thank all the staff at ETH

Zurich that are doing a great job, most of all Guido Krucker.

I would also like to thank all the people that played an important role in my education

and were not just teachers or supervisors to me, but also Mentors and eventually became

friends: Hannes Joss, Dr. Rita Oberholzer, Karl Ehrensperger, Maurice Cosandey, Jochen Müller,

Dr. Daniel Stein, Dr. Alexander Ossenbach and Professor Susan E. Gibson.

A very special thank you goes to my father Peter Gaudenz Ludwig who imparted to me

his curiosity about the world and established the basis for my scientific career. I would also

like to thank my dear friend Thomas Rast who lived this curiosity with me especially during

our childhood years and my godfather Eduard Hunziker who fuelled my eagerness to learn by

introducing me to the world of computers and electronics.

Last and mostly, I want to thank my whole family and all of my friends for their sup-

port, especially during the rough times, and I want to give a special thank you to my mother

Agustina and my sister Alexandra, os quiero mucho.

ii

Contents

Abstract x

Zusammenfassung xii

1 Introduction 1

1.1 Ferrocenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Nomenclature of enantiomerically pure 1,2-substituted fer-

rocenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.2 Synthetic routes towards enantiomerically pure 1,2-

substituted ferrocenes . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2 Aim and course of this Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2 Synthetic approaches towards PSiP-Pigiphos 17

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.1.1 Attempts to improve the Ni(II)-Pigiphos system . . . . . . . . . . 19

2.1.2 Silyl ligands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.1.3 Aim of the project . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.2 The three fundamental approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.2.1 Nucleophilic silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2.2.2 The hydrosilylation route . . . . . . . . . . . . . . . . . . . . . . . . 23

2.2.3 The Umpolung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.3 Synthetic Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.3.1 Hydrosilylation attempts . . . . . . . . . . . . . . . . . . . . . . . . 24

v

2.3.2 Attempts towards an Umpolung . . . . . . . . . . . . . . . . . . . . 25

2.3.3 Umpolung via the thioacetal . . . . . . . . . . . . . . . . . . . . . . 25

2.3.4 Synthesis and characterisation of PSi derivatives of dithiane 26 30

2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3 Synthetic approaches towards a chiral PSiP-Pincer ligand 35

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.1.1 Pincer ligands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.1.2 Pincer-like PSiP-ligands . . . . . . . . . . . . . . . . . . . . . . . . . 36


3.2 Synthetic strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.3 Synthetic challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.3.1 Synthetic approach towards the PSiP-pincer like ligand 3 . . . . 38

3.3.2 Synthetic approach towards the PPP-pincer analogue 4 . . . . . 39

3.3.3 Explanation for the synthetic difficulties . . . . . . . . . . . . . . . 40

3.4 The sulfoxophosphine ligand 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.4.1 Structure discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.4.2 Complexation Experiments . . . . . . . . . . . . . . . . . . . . . . . 43

3.4.3 Catalytic experiments . . . . . . . . . . . . . . . . . . . . . . . . . . 47

3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

4 Biferrocenylsulfoxides and Biferrocenylsulfides 51

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.1.1 Sulfoxide ligands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.1.2 Known Biferrocenyl compounds . . . . . . . . . . . . . . . . . . . . 56

4.2 Synthesis and structural features of BiFeSO 6 . . . . . . . . . . . . . . . . . . . . . . 60

4.3 Computational experiments with regard to the rotational barrier of BiFeSO 6 . . 63

4.3.1 Computational details . . . . . . . . . . . . . . . . . . . . . . . . . . 63

4.3.2 Computational results . . . . . . . . . . . . . . . . . . . . . . . . . . 63

vi

4.4 Synthesis and structural features of BiFeS 7 . . . . . . . . . . . . . . . . . . . . . . . 71

4.5 X-ray structure of BiFeSO 6b and BIFES 7 . . . . . . . . . . . . . . . . . . . . . . . . 72

4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

5 Side projects 75

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

5.2 Acidity of [Ni(II)-(Pigiphos)L]2+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

5.2.1 Fluoride Ion Affinity . . . . . . . . . . . . . . . . . . . . . . . . . . . 75


5.2.3 Synthesis of [fluoro-Ni(II)-(Pigiphos)]+ . . . . . . . . . . . . . . . 76

5.2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

5.3 Towards a chiral ferrocenyl building block . . . . . . . . . . . . . . . . . . . . . . . . 80

5.3.1 The bromo stannyl ferrocene . . . . . . . . . . . . . . . . . . . . . 80

5.3.2 The Bromo phosphino ferrocene . . . . . . . . . . . . . . . . . . . 82

5.3.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5.4 Ferrocenyl-(trifluoromethyl) sulfide . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

5.4.1 Synthetic approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

5.4.2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

6 Conclusion and Outlook 87

6.1 PSiP-Pigiphos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

6.2 PSiP-pincer like ligand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

6.3 Biferrocenylsulfoxide and Biferrocenylsulfide . . . . . . . . . . . . . . . . . . . . . . 88

6.4 Side Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

6.4.1 Acidity of [Ni(II)-PigiphosL]2+ . . . . . . . . . . . . . . . . . . . . . 88

6.4.2 Ferrocenyl building block . . . . . . . . . . . . . . . . . . . . . . . . 88

6.4.3 Ferrocenyl-(trifluoromethyl) sulfide . . . . . . . . . . . . . . . . . 89

6.5 General outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

7 Experimental 91

vii

7.1 General Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

7.1.1 Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

7.1.2 Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

7.1.3 Analytical Techniques and Instruments . . . . . . . . . . . . . . . 92

7.2 Syntheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

7.2.1 Ligands and Complexes . . . . . . . . . . . . . . . . . . . . . . . . . 93

7.2.2 Substrates and Catalyses . . . . . . . . . . . . . . . . . . . . . . . . 115

References 119

8 Appendix xiii

8.1 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii

8.2 Crystallographic Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv

8.3 Curriculum Vitae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix

viii

Abstract

This dissertation reports investigations of new chiral 1,2-disubstituted ferrocenyl compounds,

with respect to their synthesis, properties and applications.

A synthetic approach to a PSiP-Pigiphos analogue 1 was explored. Due to steric hindrance

and synthetic challenges encountered, a double substitution of silicon, by a bulky ferrocenyl

moitety was unsuccessful. Nonetheless, the approach lead to the synthesis of a PSi ligand (2),

which underwent Si–H activation with platinum(0) to yield a hydridoplatinum(II) complex

(cf. Scheme 1).

Fe

SiS S

P PtPh2 PPh3

HFe

SiSS

PPh2 H[Pt(PPh3)4]

2

Scheme 1: Si–H activation of PSi ligand 2 with [Pd(PPh3)4].

Due to the problems encountered in the PSiP-Pigiphos synthesis, the synthesis of an alternative

PSiP-pincer like ligand 3, that would form five membered metallacycles upon Si–H activation

was investigated. At the same time, the synthesis of a PPP analogue 4 was attempted, leading

to bissulfoxophosphine 5 as an intermediate compound (cf. Scheme 2).

Fe

FeRE

S Stoltol

OOECl2R

Fe

PPh2

SPh

O LDA

3: E = SiH4: E = P

Fe

FeRE

P PPh2Ph2

t-BuLiClPPh2

5: E = P, R = Ph

Scheme 2: Attempted synthesis of PSiP ligand 3 and its PPP analogue 4.

The bissulfoxophosphine 5 formed complexes with palladium(II), platinum(II) and

rhodium(I), with the partially characterised rhodium complex showing some activity in the

x

Miyaura-Hayashi reaction with low enantiomeric excess (16 %ee) and the structurally charac-

terised palladium complex showing activity in allylic substitution with enantiomeric excess up

to 78 %ee. The synthesis of PSiP ligand 3 and PPP ligand 4 both failed during the coupling

of the ferrocenyl moieties to the central donor atom, most probably due to a oxygen transfer

from the sulfoxide moiety to the eletrophile used in the synthesis.

The synthesis of a bis(ferrocenylsulfoxide) (BiFeSO) 6 was also developed (cf. Scheme 3),

resulting in two compounds that are apparent atropisomers of each other. One of the prod-

ucts 6b was fully characterised, including an X-ray structure. On basis of this data, quantum

chemical calculations were performed to test the atropisomery hypothesis. First the energy

necessary for a configurational change from 6b to 6a was calculated. The values obtained

from that calculation suggest that a configurational change would not take place at rt, there-

fore supporting the concept of two atropisomers. Furthermore, the 1H-NMR spectra for the

suggested configuration of 6a and the known configuration of 6b were calculated. The results

were in good agreement to the observed 1H-NMR signals of the ferrocenyl protons of the two

compounds. 6b was reduced to give the bis(ferrocenylsulfide) (BiFeS) 7 (cf. Scheme 3). While

complexation experiments with BiFeSO 6 was unsuccessful, BiFeS 7 seemed to eliminate iso-

butene, when reacted with mercury(II)bromide.

Fe

S t-Bu

O

Li1. CuCN

2. O2Fe

Fe

SS

t-Bu

Ot-Bu

O

NEt3SiHCl3 Fe

Fe

St-But-BuS

6 7

Scheme 3: Synthesis of BiFeSO 6 and BiFeS 7.

To complement the primary aims, three side projects were also undertaken during the course

of this work. With the estimation of the fluoride ion affinity of [Ni(II)-(Pigiphos)L]2+ in mind,

the synthesis of [fluoro-Ni(II)-Pigiphos]+ tetrafluoroborate 8 was developed. Due to the prob-

lems encountered in the synthesis of the PSiP ligand 3 and its PPP analogue 4 the synthesis

of bromo-2-(tri-n-butylstannyl)ferrocene 9 was developed with the intention to obtain an ‘in-

ert’ chiral building block, to be able to circumvent problems caused by the sulfoxide moiety. A

third side project lead to the synthesis of (Trifluoromethyl)ferrocenylsulfide 10 using the Togni

acid reagent, with the initial intention to synthesise a less rigid BiFeSO type compound.

xi

Zusammenfassung

Die vorliegende Dissertation befasst sich mit der Erforschung neuer chiraler 1,2-

disubstituierter Ferrocenverbindungen mit Bezug auf ihre Darstellung, Eigenschaften und An-

wendungsmöglichkeiten.

Die Darstellung eines PSiP Analogs 1 zu Pigiphos wurde untersucht. Die doppelte Substitution

am Silizium war nicht erfolgreich, da die einzige stabile Ausgangssubstanz für diesen Schritt

eine zu hohe sterische Hinderung aufwies. Stattdessen wurde ein PSi ligand 2 dargestellt,

welcher durch Si–H-Aktivierung mit Platin(0) einen Hydridoplatin(II) Komplex bildet (vgl.

Schema 1).

Fe

SiS S

P PtPh2 PPh3

HFe

SiSS

PPh2 H[Pt(PPh3)4]

2

Schema 1: Si–H des PSi-Liganden 2 mit [Pd(PPh3)4].

Da die Darstellung von PSiP-Pigiphos ohne Erfolg blieb, wurde die Synthese eines alternativen

pincerartigen PSiP-Liganden 3 untersucht, welcher durch Si–H-Aktivierung zwei füngliedrige

Metallacyclen bilden würde. Gleichzeitig wurde die Synthese eines PPP-Analogs 4 untersucht,

wobei Bissulfoxophosphin 5 als Zwischenprodukt gewonnen wurde (vgl. Schema 2).

Fe

FeRE

S Stoltol

OOECl2R

Fe

PPh2

SPh

O LDA

3: E = SiH4: E = P

Fe

FeRE

P PPh2Ph2

t-BuLiClPPh2

5: E = P, R = Ph

Schema 2: Versuchte Darstellung des PSiP-Liganden 3 und seines PPP-Analogs 4.

Bissulfoxophosphin 5 bildet Komplexe mit Palladium(II), Platin(II) und Rhodium(I). Während

xii

der nicht charakterisierte Rhodiumkomplex in der Miyaura-Hayashi-Reaktion nur einen gerin-

gen Enantiomerenüberschuss (16 %ee) erzeugte, konnte mit dem Palladiumkomplex in einer

allylischen Substitution ein Enantiomerenüberschuss von bis zu 78 %ee erreicht werden. Die

Synthesen des PSiP- 3 und PPP-Liganden 4 scheiterten beide während der Kupplung der Ferro-

cenyleinheiten an das zentrale Donoratom, wahrscheinlich aufgrund eines Sauerstofftransfers

der Sulfoxidgruppe auf das in der Synthese eingesetzte Elektrophil.

In einem weiteren Schritt wurde die Synthese von Bis(ferrocenylsulfoxide) (BiFeSO) 6 real-

isiert (vgl. Schema 3). Diese lieferte zwei scheinbar atropisomere Produkte. Eines der Pro-

dukte 6b konnte inklusive einer Röntgenstrukturanalyse vollständig charakterisiert werden.

Mit den daraus gewonnenen Daten wurden quantenchemische Berechnungen durchgeführt,

um die Atropisomeriehypothese zu stützen. Zunächst wurde die nötige Energie für einen Kon-

figurationswechsel von 6b zu 6a berechnet. Die daraus berechneten Energien legen nahe,

dass ein Konfigurationswechsel bei Raumtemperatur nicht stattfindet und entsprechend von

Atropisomeren ausgegangen werden kann. Weiter wurden 1H-NMR Spektren von der für 6a

berechneten Struktur, wie auch der bekannten Konfiguration von 6b berechnet, wobei die

Ergebnisse in Übereinstimmung mit den gemessenen 1H-NMR Spektren sind. 6b wurde in

einem weiteren Schritt zu Bis(ferrocenylsulfid) (BiFeS) 7 reduziert (vgl. Schema 3). Während

Komplexierungsversuche mit BiFeSO 6 keinen Erfolg brachten, schien BiFeS 7 bei der Umset-

zung mit Quecksilber(II)bromid iso-Buten zu eliminieren.

Fe

S t-Bu

O

Li1. CuCN

2. O2Fe

Fe

SS

t-Bu

Ot-Bu

O

NEt3SiHCl3 Fe

Fe

St-But-BuS

6 7

Schema 3: Darstellung von BiFeSO 6 und BiFeS 7.

Zur Ergänzung der Hauptprojekte, wurden drei Nebenprojekte verfolgt. Aus der Ab-

sicht die Fluoridionenaffinität von [Ni(II)-(Pigiphos)L]2+ zu bestimmen, wurde die Syn-

these von [Fluoro-Ni(II)-Pigiphos]+ tetrafluoroborat 8 realisiert. Aufgrund der Probleme bei

der Darstellung des PSiP- 3 und PPP-Liganden 4 wurde die Synthese vom Bromo-2-(tri-n-

butylstannyl)ferrocen 9 entwickelt. Dies in der Absicht einen “inerten”, chiralen Baustein zu

erhalten, um die von der Sulfoxidgruppe verursachten Probleme zu umgehen. In einem drit-

ten Nebenprojekt wurde die Synthese von (Trifluoromethyl)ferrocenylsulfid 10 mit dem Togni-

Säure-Reagenz entwickelt, in der Absicht ein weniger starres BiFeSO-Derivat darzustellen.

xiii

1 Introduction

1.1 Ferrocenes

Since its nearly simultaneous discovery by Keally and Pauson[1] and Miller et al.[2] in 1951,

ferrocene has been found to be a versatile component of chemical compounds that find ap-

plications in many different chemical areas ranging from homogeneous catalysis to material

sciences and biochemistry.[3–5] Its stability, which arises from its aromaticity,[6] paired with

its three dimensional structure[7–9] makes it an ideal backbone for ligands used in asymmetric

catalysis.[5,10,11]

1.1.1 Nomenclature of enantiomerically pure 1,2-substituted ferrocenes

Unlike the planar benzene homoannular disubstituted ferrocenes bearing to different sub-

stituents do not have a mirror symmetry and are therefore chiral.[12,13] The absolute configu-

ration of such planar chiral ferrocenes, is assigned following the rules proposed by Schlögel in

1967.[14] Assignement of the absolute stereochemical configuration of 1,2-disubstituted fer-

rocenes is made by looking along the C5 axis of the ferrocene from the side of the more highly

substituted Cp-ring and arranging the substituents on that ring by their Cahn, Ingold, Prelog

priorities.[15–17] The absolute configuration (R) or (S) can thus be assigned depending on the

clockwise or counterclockwise, respectively, nature of the resulting sequence of substituents

(cf. Scheme 4). If there are more than three substituents attached to the ring, only the three

with the highest priority are taken into consideration.

Fe

R2

R1

C5 axis

S configuration assumingR1 has higher priority than R2

(a)

(b) FeFe

SSO

O

(RS,RS,Ra,RFc,RFc)-Bis-[2-(t-butylsulfinyl)ferrocene]

Scheme 4: Assignment of chiral planar configuration following Schlögel’s rule.

1

1 Introduction

In order to distinguish planar chirality from other chirality units, such as central or axial chi-

rality, present in a molecule a "p" subscript is often used next to the assigned configuration.

The use of an "Fc" subscript has also become more common in ferrocene chemistry, in order

to avoid confusion with stereogenic phosphorus atoms in molecules, for which a "P" subscript

is often used. Conventionally, chiral elements have the following priorities: central > axial >

planar (cf. Scheme 4).[18]

1.1.2 Synthetic routes towards enantiomerically pure 1,2-substituted ferrocenes

Various methods have been developed to introduce planar chirality to ferrocenes, which, in

principle, can be divided into three types: A) diastereoselective directed ortho-metalation,

B) enantioselective directed ortho-metalation and C) resolution of racemic planar chiral

ferrocenes (cf. Scheme 5).[18]

In case A, a chiral auxiliary is used as a chiral directing metalation group (DMG). The

auxiliary has the ability to coordinate organolithium or lithium amide species and, through

the complex induced proximity effect (CIPE),[19] is therefore able to diastereoselectively

deprotonate one ortho position on the ferrocene. The resulting lithium ferrocene can then be

quenched with an electrophile to yield a planar chiral 1,2-disubstituted ferrocene. In order

to introduce planar chirality through CIPE, the auxiliaries feature nitrogen or oxygen lone

pair coordinating sites. In contrast, in case B, the DMG is achiral and the method relies on

chiral lithiation agents to differentiate between the prochiral ortho positions. For method C,

on the other hand, the racemate is first synthesised and later kinetically resolved, either by

enzymatic or non-enzymatic kinetic resolution.

As type A is the most developed of the methods discussed and has also been the basis for the

work described in this thesis, deeper discussion of work done using this method will follow,

while methods B and C will be discussed briefly in this section.

Early work based on enantioselective directed ortho-metalation (method B) used (–)-sparteine

on isopropylferrocene resulting in slight enantiomeric excess of 3 % ee.[20] Work done by

Price et al. using a chiral lithium alkyl amide on ferrocenyldiphenylphosphinoxide[21] resulted

in only moderate enantiomeric excesses (54 % ee).[21] The first satisfactory results based on

method B were reported almost concurrently by Tsukazaki et al. by using (–)-sparteine for the

n-BuLi mediated lithiation of N,N-diisopropyl ferrocenecarboxamide with an enantiomeric

excess of up to 99 % ee (cf. Scheme 6).[22] In addition to further reports of (–)-sparteine

mediated ortho-lithiation,[23,24] more recent work by Dixon et al. also shows the effective use

of sparteine surrogates for enantioselective ortho-lithation.[25]

2

1.1 Ferrocenes

Fe

DMG

A diastereoselective directed ortho-metallation

RLiFe

DMG

Li E+

Fe

DMG

Fe

DMG

E

E

or

enantiomerically pure

Fe

DMG

B enantioselective directed ortho-metallation

RLi / chiral diamineFe

DMG

Li E+

Fe

DMG

Fe

DMG

E

E

or

achiral

chiral lithium amide

Fe

R2

C kinetic resolution

kinetic resolution

racemate

R1

Fe

R1

R2+

Fe

R2

AFe

R1

R2+

Fe

R2

R1

Fe

R1

A+

or

Scheme 5: Three principle methods to introduce planar chirality to ferrocenes.[18]

Fe O

Ni-Pr

i-Pr1. 1.2 equiv n-BuLi / (–)-sparteine Et2O, –78°C

2. Ph2COFe O

Ni-Pr

i-Pr

CPh2

OH

91% yield 99%ee

Scheme 6: An example for method B as reported by Tsukazaki et al.[22]

3

1 Introduction

The first use of kinetic resolution on planar chiral 1,2-disubstituted ferrocenes was Horeau’s

method[26–28] as applied by Falk and Schlögl in order to determine the absolute config-

uration of (+)-1,2-(α-ketotetramethylene)-ferrocene,[29] which they isolated by reaction

with (–)-menthylhydrazide followed by multiple recrystallisations.[30] However, Horeau’s

method represents an analytical tool, rather than a useful synthetic method, as racemic

phenyl butyric acid is reacted with an enantiopure substance in order to determine the

enantiomeric excess of the unreacted phenyl butyric acid. Although stochiometric kinetic

resolution of planar chiral ferrocenes is still a topic of current investigation,[31] a more elegant

method of kinetic resolution of planar chiral ferrocenes for synthetic purposes is of a catalytic

fashion. One way to achieve this is through enzyme-catalysed asymmetric reactions that

have a long history in a variety of applications.[32] First investigations of this method were

reported in the late 1980s using baker’s yeast, while later work focused on the esterification

of 1,2-disubstituted ferrocenyl alcohols by lipase (cf. Scheme 7), giving up to 95 % ee at

32 % yield in case for Candida cylindracea lipase[33] (for a list of examples of enzymatic kinetic

resolution see Deng et al.[18] and references therein).

Fe

OHCCL, vinyl acetate

N

Fe

N

OH

+ Fe

OH

N

Fe

N

OAc

+

32% yield95%ee

42% yield92%eeCCL = Candida Cylindracea Lipase

Scheme 7: Example for enzymatic kinetic resolution as reported by Lambusta et al.[33]

A potential alternative to the enzymatic resolution is represented by the use of asymmetric

catalysis for kinetic resolution. This method was first applied in 2006 by Bueno et al. using

Sharpless asymmetric dihydroxylation.[34] In the same year, Ogasawara et al. reported a

kinetic resolution based on asymmetric ring closing metathesis (cf. Scheme 8), which became

a matter of further investigation in his group.[35–37]

4

1.1 Ferrocenes

Fe

(R)-Mo cat.

0.005 mol/l in benzene50°C, 24h

t-But-Bu

Fe

t-But-Bu

Fe

t-But-Bu

+

+Fe

t-Bu

t-Bu

2

47% yield95%ee

46% yield96%ee

3% yield(R)-Mo cat.

t-Bu

t-Bu

OOMo

N

i-Pr

i-Pr

MePh

Me

(rac)

Scheme 8: Asymmetric ring closing metathesis as reported by Ogasawara et al.[38]

1.1.2.1 Ugi-approach Although the first synthesis and isolation of (rac)-[1-

(dimethylamino)ethyl]ferrocene 11 was already reported in 1957 by Hauser and Lindsay,[39]

no special interest was given to this material until resolution with (R)-(+)-tartaric acid as

well as its use in diastereoselective ortho lithiation was reported by Ugi and co-workers.[40,41]

Due to the tertiary amine 11’s importance to the synthesis of chiral ferrocene derivatives, it

has become known under the trivial name Ugi’s amine.

Synthesis of Ugi’s amine. Many attempts towards the improvement of the synthesis of

optically pure Ugi’s amine have been reported,[42–48] among which enzymatic methods[43,48]

as well as Corey-Bakshi-Shibata reduction[44–46] proved to be applicable on a multi-kilogram

scale.[46,48] However, the most widely used synthetic route is based on the synthetic route,

improved to limit the formation of vinyl ferrocene in the alcohol activation step, reported

by Ugi’s and co-workers in 1972[42,49] (cf. Scheme 9). Resolution is still performed using

(R)-(+)-tartaric acid to crystalise the (S)-11 tartrate from methanol. The (R)-11 tartrate is

then recovered through evaporation of the mother liquor and recrystallisation from aqueous

acetone.[40,49]

5

1 Introduction

Fe FeCH3COCl

AlCl3, DCM

O

LiAlH4

benzeneFe

OH

HOAc

benzene

Fe

OAc

HNMe2

MeOHFe

NMe2

resolutionFe

NMe2

Fe

NMe2

(S)-11 (R)-11(rac)-11

+

Scheme 9: Synthesis of Ugi’s amine.[40,49]

Use in synthesis of 1,2-disubstituted ferrocenes. Ugi and co-workers showed, that

treatment of (R)-11 with n-BuLi leads to a directed ortho-lithiation.[40,41] This is due to the

interaction with the nitrogen lone-pair, which stabilises the lithium ion at one of the ortho

positions more favourably than the other. Inspection of the two possible diastereomers of

lithiated (R)-Ugi’s amine 12 reveals that (R,SFc)-12 is disfavoured due to the steric interaction

of the methyl group with the Cp′-ring, whereas the (R,RFc)-12 diastereomer can be formed

without any steric hindrance. This interaction results in a diastereomeric ratio up to 96:4 dr

for the final products, as demonstrated by quenching with a variety of electrophiles[40] (cf.

Scheme 10).

Fe

NMe2

(R)-12

LiFe

(S)-12

Li

NMe2 E+

Fe

NMe2E

up to 96:4drsteric repulsion

Scheme 10: Selective ortho lithiation of Ugi’s amine.[40,41]

As the resulting products are diastereomers, separation of the major and minor product can

usually by achieved by flash column chromatography or crystallisation yielding the major di-

6

1.1 Ferrocenes

astereomer in high purity. In a further step, the dimethylamino group of the ortho-substituted

Ugi’s amine 13 can be substituted by convertion to a leaving group, e.g. under acidic

conditions or by methylation of the amine. Ugi and co-workers reported that substitution of

the amine takes place with full retention.[50] They stated that the reaction seems to follow

a non-classical SN 1-mechanism, in which the N–C bond is cleaved simultaneously with the

Fe–C bond to form a carbenium ion. As a matter of fact, the stabilising effect of ferrocene

on adjacent carbenium ions was already known and had been thoroughly investigated at the

time,[51,52] leading to the conclusion that there is a significant interaction between iron and

the double bond formed during an elimination process, resulting in an 18 e− configuration

of the formal Fe(III) centre.[53,54] The masked carbenium ion 14 is then attacked in an exo

fashion by a nucleophile, resulting in retention of the configuration (cf. Scheme 11).

Fe

LG: e.g. HNMe2+,NMe3

+,OAc

LG

HMe

Fe+H

Me

14

Nu-

Fe

Nu

HMe

Scheme 11: Non-classical SN 1-mechanism for the substitution at the "benzylic" carbon.[53,54]

Due to these properties, Ugi’s amine is used a the starting material for a wide variety of

ferrocene-based ligands with central and planar chirality having applications in asymmetric

catalysis.[55–68] Some of these ligands can be synthesised in a simple two step reaction from

Ugi’s amine, as in the case of Josiphos (cf. Scheme 12).

Fe

NMe2

Fe

NMe2

Fe

PCy2PPh2 PPh2

(R)-11 (R,SFc)-PPFA (R,SFc)-Josiphos

1. n-BuLi,THF, –78°C2. ClPPh2

HPCy2

AcOH, 80°C

Scheme 12: Synthesis of Josiphos.

7

1 Introduction

1.1.2.2 Sulfoxide approach A more recent approach towards the synthesis of chiral 1,2-

disubstituted ferrocenes is based on chiral ferrocenyl sulfoxides. Their use in diastereoselec-

tive ortho-lithiation was first reported in 1993 by Kagan and co-workers.[69] The chiral ferro-

cenyl sulfoxides used for the directed ortho-lithiation are readily accessible through enantio-

selective oxidation of the sulfide[69–71] or by nucleophilic attack of lithioferrocene on optically

pure sulfinates[72–75] or thiosulfinates[76–79] (cf. Scheme 13).

Fe

LiOSp-tol

O

SS

O

Fe Fe

S Sp-tol

O O

Fe

S 1 equiv cumene hydroperoxide1 equiv Ti(Oi-Pr)4

2 equiv (S,S)-diethyl tartrate1 equiv H2O

Fe

SO

Scheme 13: Synthetic routes to chiral sulfoxides.[69–79]

Use in synthesis of 1,2-disubstituted ferrocenes. Ortho-lithiation of ferrocenyl sulfoxides

is usually effected by addition of n-BuLi or LDA, depending on the other sulfoxide substituent

(cf. Scheme 14). Like the nitrogen lone-pair in the case of Ugi’s amine (vide supra), the oxygen

lone-pair of the sulfoxide facilitates ortho-lithiation, favouring the lithiated diastereomer with

the sulfoxide substituent anti to the ferrocene. Therefore, the two commonly used ferrocenyl

sulfoxides (RS)-t-butylferrocenylsulfoxide 15 and (SS)-p-tolylferrocenylsulfoxide 16 give

1,2-disubstituted ferrocenes with opposite planar chirality (cf. Scheme 14).

An advantage of p-tolylsulfoxide 16 over t-butyl sulfoxide 15 is the possibility to replace the

8

1.1 Ferrocenes

Fe

S p-tol

O

LDAFe

Sp-tolOLi

TMSClFe

S p-tol

OTMS

Fe

S t-Bu

O

Fe

St-Bu

OMeI

Fe

S t-Bu

O

Li Men-BuLi

Scheme 14: Diastereoselective ortho lithiation of sulfoxides.[75,77]

sulfoxide by another substituent through attack with either t-BuLi[75] or PhLi[80] forming

the corresponding sulfoxide and lithioferrocene species. Subsequent quenching of the

lithioferrocene with an electrophile gives access to a large variety of ligands[81] (cf. Scheme

15).

Fe

S p-tol

OR

t-BuLi

t-BuS

p-tol

OFe

RLi

E+Fe

RE

Scheme 15: Substitution of p-tolyl sulfoxide.[75]

1.1.2.3 Chiral acetal approach Another approach towards enantiopure 1,2-disubstituted

ferrocenes developed in Kagan’s group utilises the chiral acetal 17 and was reported by Riant et

al. in 1993.[82] The methoxymethyl dioxane 17 is readily accessible from ferrocene by a three

step synthesis with an overall yield of 82 % (cf. Scheme 16). The (S)-(–)-1,2,4-butanetriol

needed for the synthesis of hydroxymethyl acetal 18 can be readily obtained by reduction of

(S)-(–)-malic acid with borane.[83] Therefore, the approach is also economically viable. The

9

1 Introduction

directing effect in ortho lithiation arises from the stabilising effect of the methoxy group and

one of the dioxane oxygen atoms, which chelate the lithium at the ortho position that leads to

Fe

O

(MeO)3CH

p-tolyl sulfonic acid80°C

Fe

O

O (S)-(–)-1,2,4-butanetriol

camphor sulfonic acidCHCl3, 4Å, rt

Fe

HOO

OH

18, 85%

1. NaH, THF, 0°C

2. MeI Fe

HOO

O

17, 97%

Scheme 16: synthesis of the chiral acetal 17.[84]

the most favourable chelation ring, resulting in the (S)-lithioferrocene 19 yielding the product

in a diastereomeric ratio of 99:1 dr[82] (cf. Scheme 17). Most probably, the orientation of the

oxygen, which is not involved in the lithium chelation towards the iron moiety may have a

major impact on diastereoselectivity. In the case of (R)-19 this atom is positioned endo with

respect to the iron centre, whereas in (S)-19 it is oriented exo.[84] It has also been shown, that

the directing effect is of kinetic origin, since the diastereomeric excess decreases significantly

if the reaction temperature is raised, with 95:5 dr at 0 ◦C.[82]

The directing acetal can be removed by hydrolysis after planar chirality has been introduced.

The resulting enantiopure 2-substituted formylferrocene has proven useful for synthesis of a

large variety of chiral ferrocenyl compounds (cf. Scheme 18).

1.1.2.4 Oxazolines Enantiomerically pure ferrocenyl oxazolines are readily synthesised

from ferrocenylacyl chloride and the corresponding amino alcohol (cf. Scheme 19). The enan-

tiomerically pure amino alcohols can be generated through the reduction of amino acids,[85,86]

whereby a large variety of chiral oxazolines are accessible.

10

1.1 Ferrocenes

H

Fe

HOO

O

t-BuLi

Fe

OO

OLi

Fe OO

OLiH

(S)-19

(R)-19

E+

Fe

HOO

O

E

99:1dr

–78°C

Scheme 17: Diastereoselective ortho-lithiation of acetal 17.[82,84]

Fe FePPh

Fe

FeN NH

Fe

Fe

OH

HO

Scheme 18: Ligands synthesised by following the acetal approach.[87–90]

Directed ortho-lithiation of enantiopure ferrocenyl oxazolines has been performed by the

treatement of the oxazoline with n-BuLi or s-BuLi in ethers at –78 ◦C giving a diastereomeric

excess up to 97:3 dr.[91–95] An alternative experimental procedure using hexanes as solvent

and TMEDA gave an diastereomeric excess of >99:1 dr. This method was designed by Sam-

makia et al. in order to test their hypothesis for directed ortho lithiation.[93,94] They proposed

that control of diastereoselectivity is derived from the steric interaction of the bulky group on

the oxazoline with the butyl group of the butyllithium, rather than the interaction with the

ferrocene. Therefore the stereo information would be imparted in the transition state of the

deprotonation of the ortho position (cf. Scheme 20). However, other factors that may influ-

ence the diastereoselectivity exist and they should still be taken into consideration.

11

1 Introduction

Fe

Cl

O OHH2N

R1. , Et3N, CH2Cl2

2. a, b or c

a: TsCl, Et3N, cat. DMAP, CH2Cl2b: SOCl2, 20% K2CO3 (aq.)c: PPh3, CCl4, NEt3, CH3CN

Fe

O

NR

Scheme 19: Synthesis of enantiomerically pure ferrocenyl oxazolines.[92,93,95]

Fe

O

NR

BuLi

Fe

H

Li Bu

NO

RFe

H

LiBu

NO

R steric repulsion

major minor

Fe

O

NR

Fe

O

NR

E+

E

E

major minor

Scheme 20: Diastereoselective ortho lithiation of ferrocenyl oxazolines.[93,94]

Hydrolysis of the oxazoline could be considered as a feasible method to replace the oxazoline

by another functionality. However, the donor features of the oxazoline make it useful as coor-

dination site for complexation and thus render an exchange unnecessary for the synthesis of

chiral ligands. This is one of the major advantages of the oxazoline approach,[18] as it gives ac-

cess to asymmetric bidentate ligands in only a single reaction step, complementing the already

large variety of oxazoline ligands[96,97] with their ferrocene derivatives.

12

1.1 Ferrocenes

1.1.2.5 Directing groups containing phosphorus A variety of aryl phosphine deriva-

tives have been shown to have an ortho directing effect upon metallation.[98–103] The

diastereoselective ortho metallation utilising chiral ferrocenyl phosphine derivatives seems

somewhat obvious. However, only a few successful examples are known. One of these is the

ortho-magnesiation reported by Nettekoven et al.[104–106] (cf. Scheme 21). A diastereoselective

excess of 97:3 dr in quantitative yield was achieved, using iodine as the electrophile.

Fe

PO

R

Fe

MgOP

Fe

Mg OP

major minorsterical repulsion

(i-Pr)2NMgBr

I2

Fe

PO

RI

97:3dr

R:

Scheme 21: Diastereoselective ortho magnesation reprted by Nettekoven et al.

Another successful example is that of the oxazaphospholidine-oxide reported by Xiao and

co-workers,[107–109] which undergoes diastereoselective ortho-lithiation with t-BuLi, giving

a diasteremeric excess of >99:1 dr in yields varying between 45 – 95 %, depending on the

electrophile. They also discovered, that the yield decreases significantly with the use of n-BuLi

as lithiating agent, due to reaction with the phosphorus moiety (cf. Scheme 22),[107] which is

a general problem in directed ortho lithiation of phosphine derivatives.[103] An example using

a P(III) instead of a P(V) phosphorus derivative was patented by Pfaltz et al.,[110] who used a

borane protected phosphine bearing chiral amidites to yield 1,2-disubstituted ferrocenes with

99:1 dr (cf. Scheme 23).

13

1 Introduction

Fe

PO

ON

Ph1. t-BuLi, –78°C

2. E(X)

E(X) = Me(I), I(I), TMS(Cl), TES(Cl), Ph2CO, B(OMe)3, PR2(Cl)

Fe

PO

ON

PhE

>99:1dr

Fe

PO

ON

Ph1. n-BuLi, –78°C

2. MeIFe

PO

ON

PhMe

>99:1dr, 33%

Fe

PO

n-BuN

MeO

Ph

50%

Scheme 22: Diastereoselective ortho lithiation of oxazaphospholidine-oxide as reported by Xiao and

co-workers.[107–109]

Fe

P

BH3

N

N

OMe

OMe

1. s-BuLi, Et2O, –78°C

2. E(X) Fe

P

BH3

N

N

OMe

OMe

E

E(X) = TMS(Cl), PPh2(Cl), Br(CF2CF2Br)

Scheme 23: Diastereoselective ortho lithiation as reported by Pfaltz et al.[110]

14

1.2 Aim and course of this Thesis

1.2 Aim and course of this Thesis

The initial motivation behind this thesis was to improve the Ni(II)-Pigiphos system that

was developed in the Togni group. The main problems encountered with the dicationic

Ni(II)-Pigiphos system arose from its strong bonding not only to the substrate, but also to

coordinating solvents as well as, in the case of the Nazarov cyclisation, the product (for detail

cf. Section 2.1). As a consequence the catalyst gets poisoned during the reaction. In order

to facilitate the release of the product from the Ni(II) catalyst in the Nazarov cyclisation and

therefore facilitate the completion of the catalytic cycle, a new ligand design was propound

that lowers the lewis acidity of the catalytic system and therefore weakens the bond of the

metal at the active site. A silyl donor as central coordination site in the ligand would meet

this goal. First, the decreased charge of the complex would already have an impact on Lewis

acidity. In addition the silyl donor is a stronger σ-donor than the phosphine, which results

in further elevation of the energy levels of the orbitals involved in σ-bonding. In case of

a square-planar complex this concerns orbitals with a1g, b1g and eu symmetry, therefore

including dz2 (a1g) and dx2−y2 (b1g), which represent HOMO and LUMO of a square planar

complex (cf. Scheme 24). As a consequence the release of the weakest bound ligand should

HOMO

LUMO

increase of σ-donation

free metal

Scheme 24: Effect of σ-donation on the MO diagram of a square planar complex.

be facilitated resulting in a higher accessibility of the active site. Therefore, the synthesis of

a PSiP-Pigiphos 1 analogue and the comparison of the PPP- and PSiP-Ni(II)-Pigiphos systems

with respect to their properties and catalytic activity was the initial goal of this thesis (cf.

Chapter 2). As the synthesis of a PSiP-Pigiphos analogue was unsuccessful, a simplification of

the system to an alternative PSiP 3 and PPP 4 tridentate ligand was considered (cf. Chapter

3). Synthetic difficulties encountered in the coupling of the two ferrocene moieties to the

15

1 Introduction

central donor atom made the isolation of the desired products unfeasible. Nonetheless,

a bis(sulfoxo)phosphine 5 was isolated as an intermediate in the attempted synthesis of

the PPP-pincer 4. This bis(sulfoxo)phosphine 5 formed κ2-complexes with palladium(II),

platinum(II) and rhodium(I), which also showed asymmetric catalytic activity. This sparked

interest in sulfoxide ligands leading to the design and synthesis of the bis(ferrocenylsulfoxide)

6 (cf. Chapter 4).

Fe

SiX

Fe

PPh2 Ph2P

R

Fe

FeSi

P PH

R

Ph2Ph2

Initial PSiP-Pigiphos analogue

Fe

FeP

P P

R

Ph2Ph2

Bis(sulfoxo)phosphineisolated as intermediate

Fe

FePhP

S Stoltol

OOFe

Fe

SS

t-Bu

Ot-Bu

O

1

Simplified PSiP and PPP system

3 4

5

Focus on a pure sulfoxide ligand

6

Scheme 25: General conceptual scheme.

16

2 Synthetic approaches towards PSiP-Pigiphos

2.1 Introduction

Ferrocenyl-based ligands developed for application in asymmetric catalysis have a long history

within the Togni group. Besides the well-known bidentate phosphine ligand Josiphos, a variety

of different ferrocene-based ligands (cf. Scheme 26) have been created and studied by former

and current members of the Togni group. Among these is the tridentate phosphine ligand

Pigiphos, which was first synthesised by Pierluigi Barbaro[60] following a straightforward two

step synthesis starting from commercially available Ugi’s amine (cf. Scheme 27).

Fe

NN R'

R''PPh2

Fe

PFe

PPh2 Ph2P

Cy

Fe

FeN NH

Fe

PCy2PPh2

Fe

FePCy

Josiphos

Pigiphos

Scheme 26: Selection of ferrocene based ligands synthesised in the Togni group.

Pigiphos readily forms complexes with a wide variety of late transition metals,[60,112–115]

whereby the first reported asymmetric catalysis with the ligand used a ruthenium(II)-Pigiphos

complex for transfer hydrogenation of acetophenone.[112] Special interest has been taken in

the dicationic nickel(II)-Pigiphos complex, which was first synthesised and used for asymmet-

ric acetalisation by Barbaro.[113] As a chiral lewis acid it was also used as a catalyst for hy-

droamination,[111,116] hydrophosphination,[117,118] Nazarov-cyclisation[119,120] and 1,3-dipolar

17


Fe

N1. t-BuLi2. ClPPh2

Et2O, -78 °C Fe

NPPh2

CyPH2, TFAAcOH, 80 °C

Fe

PFe

PPh2 Ph2P

Cy

Scheme 27: Two step synthesis of (R)-(SFc)-Pigiphos derivatives starting from Ugi’s amine.[111]

OCO2R2

R3Ph

R1

20a-h 21a-h

i) [Ni(II)-Pigiphos](ClO4)2in situTHF, rt

ii) CH2Cl2, rt

O

R1

Ph

CO2R2

R3

Compound R1 R2 R3 Yield (%) ee (%)

21a Me Et TMPa 84 86

21b Ph Et TMPa 85 87

21c Me Et PMPb 32 71

21d Ph Et PMPb 96 83

21e Me Pr TMPa 80 82

21f Ph Pr TMPa 82 88

21g Me Bn TMPa 58 45

21h Me Npc TMPa no reaction n.a.

Reaction times for full conversion are 6 – 8 d for substrates having R3=TMP

and 9 – 15 d for R3=PMP. a TMP= 2,4,6-trimethoxyphenyl. b PMP=4-

methoxyphenyl. c Np=1-naphtyl.

Table 1: Ni-catalysed Nazarov cyclisations of various dialkenyl ketones[120]

cycloaddition reactions. Despite this variety of applications of the dicationic Ni(II)-Pigiphos

complex the strong binding of the dicationic Ni(II)-Pigiphos complex to coordinating solvents

is a considerable problem, that leads to catalyst poisoning and therefore low TON. Similarly,

in case of the Nazarov-cyclisation the strong binding of Ni(II)-Pigiphos to the product in the

catalytic cycle , leads to low TON, as well as long reaction times due to low TOF (cf. Table 1).

18

2.1 Introduction

2.1.1 Attempts to improve the Ni(II)-Pigiphos system

In order to overcome the above mentioned activity problems, the introduction of an N-

heterocyclic carbene (NHC) moiety as a replacement for the central phosphorus donor site

in the Ni(II)-Pigiphos system was undertaken in our group. NHCs display similar bonding

properties to trialkylphosphines,[121,122] but with the benefit of being much stronger σ-donors

in most cases. Although the synthesis of the NHC bearing Pigiphos analogue 22 has been

performed successfully (cf. Scheme 28),[123] it turned out to have major disadvantages due

to the flexibility of the system caused by the additional bridging carbon atoms between the

ferrocene and the carbene moiety. Not only were lower enantiomeric excesses observed,

but in most cases no advantages over the Pigiphos catalytic system could be discerned. In

addition to the above mentioned conformational flexibility, the NHC-Pigiphos derivative

also showed relatively weak coordination of the NHC moiety to metal centres. For example,

an extraordinarily long NHC-Pd bond of 2.040(12) Å[123] is observed in the Pd(II) iodo

complex of this ligand. This unusually long distance between the donor ligand and metal is

most likely a result of disfavoured seven membered metallacycles formed by coordination

of the phosphine groups. As a consequence of these results and observations, an alternative

modification of Pigiphos was thought to be necessary.

Fe

NMe2 1. t-BuLi, Et2O2. ClPPh2

3. AcOAc, 2-5 h,100 °C

Fe

OAcPPh2

1. Imidazole, AcCN/H2O

2. NaI, EtOH, 3 h, rt Fe

FeN N

HPPh2 Ph2P

22

Scheme 28: Synthesis of the NHC-Pigiphos analogue 22.

19


2.1.2 Silyl ligands

Although Wilkinson reported the first transition metal silyl derivative as early as 1956,[124] the

developement of the field was initially slow.[125] Only after the discovery of transition-metal-

catalysed hydrosilylation of alkenes[126] and the importance of the Si–H activation by oxidative

addition behind it,[127] did interest in the area start to grow. Silyl ligands are particularly

strong σ-donors and have been shown to have a strong trans influence. X-ray crystallographic

analyses show Pt–Cl bond lengths trans to the silyl donor are up to 0.161 Å longer than those

in PtCl2−4 with Pt–Cl bond lengths of 2.465 (2) Å in case of the triphenylsilyl platinum com-

plex 23 (cf. Figure 1).[128] This fact, together with the low frequency IR signals for ν(Pt–Cl)

at 239 cm−1[129] observed are clear indicators of the strong trans influence of silicon donor

ligands.

PtClSi

P2

P1

Figure 1: X-ray structure of the triphenylsilyl platinum complex 23.[128]

Currently, there is a special interest in incorporating silyl donors into ancillary ligand frame-

works. In such a framework, the strong trans labilising σ-donor properties of the silyl donor

can be fully utilised.[130] Such ligands form coordinatively unsaturated complexes and have

been purported to show enhanced reactivities.[131,132] Many complexes of this type have been

reported and some have shown interesting catalytic activity.[132–144] There are a variety of

methods to form Si–M bonds in a complex. Among the most common is Si–H activation. As

Si–H bonds are known to be more reactive toward oxidative addition than other Si–X bonds,

this represents one of the most viable paths to Si–M complexes. Methods using transition

metal anions or silyl anions have also been reported.[125]

20

2.2 The three fundamental approaches

2.1.3 Aim of the project

Due to the problems encountered in catalysis with Pigiphos and the known properties of silyl

donors, it was assumed that reactivity, in terms of TOF, could be enhanced if a PSiP-Pigiphos

analogue could be synthesised and applied. The strong trans labilising effect of the silyl

donor should lead to an increased exchange rate at the active site as well as a weakening

of the product–catalyst complex. The only potential drawback of such an approach may be

the monocationic character of the Ni(II)-PSiP-Pigiphos complex formed, the Lewis acidity

of which might be lowered to the point at which it no longer activates the substrate. This

particular problem might be overcome by chosing a different metal-ligand system, thus

adding intrinsic value to the proposed PSiP ligand class. Therefore, the aim of this work is

to prepare a PSiP-Pigiphos analogue and complex it, by Si–H activation, to form a catalytic

system comparable to the Ni(II)-Pigiphos system discussed above.

Fe

SiX

Fe

PPh2 Ph2P

R

X = H, ClR = Me, Ph

1

Scheme 29: Generalised structure of the proposed PSiP-Pigiphos ligand 1


To synthesise a PSiP-Pigiphos ligand 1 three different approaches were considered (cf. Scheme

30). Based on the known Pigiphos synthesis from Ugi’s amine (vide supra), a nucleophilic

silicon reagent would be most useful. Hydrosilylation of a vinyl ferrocene or Umpolung of the

"benzylic carbon" at the ferrocene would also be effective strategies for the formation of the

desired ligand systems.

21


Fe

SiX

Fe

PPh2 Ph2P

R

FePPh2

FePPh2

FePPh2

LG

M

+ RSiH2X + RSiM2X

+ RSiCl2X

Hydrosilylation route Nucleophilic silicon route

Umpolung route

1

Scheme 30: Three fundamental retrosynthetic routes to synthesise PSiP-Pigiphos 1

2.2.1 Nucleophilic silicon

The simplest form of a nucleophilic silane moiety, is the analogue of the carbanion, which

here may be referred to as silicon anions for simplicity. As a matter of fact, silicon anions

have been the subject of investigation for the better part of the past century.[145–148] Usu-

ally, symmetrically substituted disilanes are treated with alkali metals in ether solution to

give alkali silicides. Metallation of halosilanes has also been reported, whereby a disilane is

formed in a Würtz-coupling-type reaction which is then cleaved by the alkali metal. Finally,

deprotonation of certain silanes by potassium hydride has been observed as well.[149] One

of the most common silyllithium compounds is triphenylsilyllithium, the reaction of which

with diphenylphosphinoacetylferrocene could provide a starting point for PSiP-Pigiphos, since

the phenyl substituents on silicon may be readily removed with triflic acid.[150] The resulting

silyl triflate may be lithiated a second time leading to the desired product in a multistep syn-

22


thesis (cf. Scheme 31). However, the harsh reaction conditions and multistep synthetic route

render such an approach a significant challenge.

Fe

SiX

Fe

PPh2 Ph2P

R

FePPh2

X LiSiPh3

FePPh2

SiPh3

FePPh2

SiPh2

HOTf

LithiationOTf

1

Scheme 31: Theoretical multistep synthetic route towards PSiP-Pigiphos using silyl lithium.

Rhodium(I) or copper(I) activated Si–B bonds may also act as silyl nucleophiles. Nucleophilic

silicon compounds of this nature form the corresponding silicon cuprate or rhodate in cat-

alytic quantities. To date, these metal-silicon compounds have been reacted with electrophiles

such as aldehydes or α,β-unsaturated carbonyls.[151,152] This kind of reaction has only been

reported for monoborylsilanes. Therefore, this approach to the synthesis of PSiP-Pigiphos,

requiring boryl silanes, is also synthetically complicated, since the boryl silanes are synthe-

sised from corresponding chlorosilanes in a multistep process, hence resulting in a complex,

multistep synthesis of the desired product.

2.2.2 The hydrosilylation route

Since the first use of the term "catalytic hydrosilylation" by Ojima et al.[153] many new cat-

alytic systems have been reported,[154,155] and the method has been developed into one of the

most important uses of homogeneous platinum catalysis, second in importance only to the vul-

canisation of silicone rubber.[156] Considering the ready accessibility of vinyl ferrocenes from

Ugi’s amine[157] hydroslilylation may be a feasible synthetic strategy for a PSiP backbone. The

only foreseeable pitfall of this method may arise from anti-Markovnikov addition to the vinyl

group, which would lead to a C2 tether instead of a C1 tether between the silicon moiety and

the ferrocenyl unit.

23


2.2.3 The Umpolung

As chlorosilanes are not only good electrophiles but are also commercially available in many

varieties, an Umpolung of the benzylic position of a ferrocene derivative might be a straight-

forward path towards the synthesis of a PSiP-Pigiphos. Different approaches towards such

an Umpolung may be considered. Although Gmelin reports the existence of ferrocenyl-

(chlorozirconocenyl)-methane,[158] the original literature[?, 159] shows that, as one would ex-

pect, the hydrozirconation of formyl ferrocene using Schwartz’ reagent results in the zir-

conocene bound to oxygen, with the hydrogen adding to the adjacent carbon. However,

such an approach could be considered, as well as the potential hydrozirconation of a vinyl

ferrocene, despite the potential for the formation of a C2 tethered system.

A further approach would be a Corey-Seebach-Umpolung[160], which is a simple method for

the synthesis of acylsilanes.[161] This method has already been demonstrated for formyl fer-

rocene by Reuter et al.[162] By using an enantiomerically pure formyl ferrocenyl phosphine,

this seems a tantalisingly elegant approach. Kondo et al. described a synthetic route to fer-

rocenylmethyllithium in the early 1970s, through reductive lithiation of ferrocenylmethyl-

methoxide.[163,164] Two decades later Knochel and co-workers claimed a similar approach to

stable α-ferrocenyllithium derivatives starting from α-thioethers, -ethers and -amines.[165] In

this case, the approach via the amine is of interest since Ugi’s amine may be used to introduce

planar chirality (cf. Paragraph 1.1.2.1).

2.3 Synthetic Results

The different approaches towards the synthesis of PSiP-Pigiphos mentioned in the introduction

of this chapter were investigated in parallel to determine, as quickly as possible, which would

be the most feasible. Application of a nucleophilic source of silicon was ruled out during

preliminary investigations, due to the foreseen difficulties concerning harsh reaction condi-

tions combined with a long multistep reaction path (vide supra). The respective reaction paths

and the associated difficulties are discussed in more detail to clarify the choice of synthetic

approach.

2.3.1 Hydrosilylation attempts

Although hydrosilylation is a widely used method for introduction of silicon or a hydroxy group

into a molecule, its use on vinylferrocenes is largely unkown. The work by Morán et al. on oc-

takis(dimethylsiloxy)octasilsesquioxanes[166] is often cited, as is Losada’s work on ferrocenyl

24


functionalised silane based dendrimers.[167,168] Both use Karstedt’s catalyst for the reaction

with tertiary silanes. Regrettably, their catalytic system failed to yield hydrosilylation products

when chlorophenylsilane or chloromethylsilane were used in combination with vinylferrocene

or (diphenylphosphino)vinylferrocene.

Other attempts using chloroplatinic acid, a known catalyst for the hydrosilylation of styrenes

by chlorosilanes,[169,170] did not result in the desired product, regardless of substrate. Due to

the failure of these experiments to produce the target compounds and the fact that hydrosi-

lylation should lead to the less favoured C2-tethered product, efforts along this route were

ceased.

2.3.2 Attempts towards an Umpolung

An Umpolung strategy by reductive lithiation as described by Knochel and co-workers[165] was

one of the first methods for the generation of silylated ferrocenyl materials pursued in this

work. Despite several attempts to follow this reaction protocol, the results proved unrepro-

ducible. A hydrozirconation approach, as described by Etiévant,[159,171] was performed in two

test reactions with formyl ferrocene which indicated that starting materials were consumed,

but the products of these trials could not be isolated. Meanwhile, an Umpolung following

the Corey-Seebach route[162] was successful and the focus of further experiments was directed

towards this particular approach.

2.3.3 Umpolung via the thioacetal

Initially, planar chirality was imparted to the ferrocene derivative, by following the reaction

protocol of Riant et al.[84] The chiral acetal 18 was synthesised in a two-step reaction from

formyl ferrocene, by using (S)-(–)-1,2,4-butanetriol, which can be readily prepared from (S)-

malic acid by reduction with borane,[83] to introduce stereochemical information. Deproto-

nation of the hydroxy group followed by methylation leads to the ether 17 which undergoes

selective ortho lithiation of the ferrocene moiety, when reacted with t-butyllithium. Quench-

ing the lithiated species of 17 with chlorodiphenylphosphine gave compound 24, which un-

derwent an acetal exchange in HCl-saturated benzene with 1,3-propanedithiol to give the

thioacetal 25 in an overall yield of about 13 % (cf. Scheme 32).

Recrystallisation of the thioacetal from DCM/n-hexane 25 gave single crystals suitable for X-

25


Fe

O

H TSA

HC(OMe)3 Fe

HO O

CHCl3, MS 4Å

HO OHOH

Fe

HO O

OH

NaH, MeI

THF

Fe

HO O

OMe1. t-BuLi2. ClPPh2

Et2O Fe

HO O

OMe

PPh2

1,3-propanedithiol, HCl

benzene Fe

HS S

PPh2

99%48%

82%82% 41%

25

18

17 24

Scheme 32: Multistep reaction path towards phosphinoferrocenyl-1,3-dithiane 25.

P1

C17

C11C1 C5

S2

S1C23

Figure 2: X-ray structure of the phosphinodithiane 25.

ray crystallography (cf. Figure 2). In order to judge the importance of the structural features

from the X-ray structure of compound 25 the structural parameters were compared to those

for 1,1′-bis(1,3-dithian-2-yl)ferrocene 26 reported by Hartinger et al.[172] as well as the 1,1′-

bis(diphenylphosphenyl)-2,2′-bis(1,3-dioxan-2-yl)ferrocene 27 reported by Connell et al.[173]

(cf. Scheme 33).

26


Fe

HS S

PPh2Fe

HS S

Fe

HO O

PPh2

HS S

HPh2P

O O2526 27

Scheme 33: Compounds used for structural comparison. From left to right: dithioacetal 26,[172]

phosphinothioacetal 25 and bisdiphenylphosphino diacetal 27.[173]

The bond lengths of the substituents to the ferrocene are largely the same, with their bond

length differences within the experimental standard deviations calculated. In order to assess

the conformational differences between the structures, φ1 was defined to be the angle be-

tween the Cp-plane and the plane including the base of the trigonal pyramid formed by C(5),

S(1), S(2) and C(23), with C(23) being the apex of the pyramid. This angle was compared

with the angle between the planes passing through the respective atoms of compounds 26

and 27. Interestingly, in case of Hartinger’s bis(dithianyl)ferrocene, φ1 varies significantly be-

tween the two thioacetal groups, having the values of 76.4° and 84.2°. Regardless of the fact

that the values for the bis(dithianyl)ferrocene differ so much from each other, the value of φ1

for compound 25 is still significantly smaller at 66.4°, while the ferrocenyl acetal reported by

Connell shows angles for φ1 of 59.8° and 54.0° respectively (cf. Table 2).

Compound 26 [°] Compound 25 [°] Compound 27 [°]

76.4 66.4 59.8

84.2 54.0

Table 2: Angles φ1 between the Cp ring and the (thio)acetal.

The influence of the torsion angle of the thioacetal or acetal on the orientation of the

diphenylphosphine group is unclear, as is the influence of substitution of both the Cp and

the Cp′ in Connell’s case as compared to compound 25, which is only substituted on one Cp

ring. To compare the orientation of the phosphine, two angles are defined, φ2 as the dihe-

dral angle C(17)–P(1)–C(1)–C(5) and φ3 as the dihedral angle C(11)–P(1)–C(1)–C(5) and

the corresponding angles in Connell’s diacetal. In compound 25 φ2 has a value of 87.1(2)° in

comparison to the φ2 in Connell’s diacetal measuring 107.4° and 115.7°, for φ3 the value is

27


170.0(2)° in 25 and 147.8°, 138.9°, respectively, in Connell’s diacetal (cf. Table 3). φ2 and φ3

can be used as an indicator for the orientation of the phosphorus’ lone-pair.

φ2 φ3

Compound 25 [°] Compound 27 [°] Compound 25 [°] Compound 27 [°]

87.1(2) 107.4 170.0(2) 147.8

115.7 138.9

Table 3: Dihedral angles along the phosphine–ferrocene bond.

The phosphorus lone-pair, appears to be oriented towards the thioacetal moiety in 25. At the

same time the value of φ1 implies an orientation of the acidic hydrogen of the thioacetal to-

wards the phosphine lone-pair. As the measured distance between C(23) and P(1) of 3.42 Å

is comparable to the sum of the van der Waals-radii of phosphorus and carbon, which would

be 3.5 Å,[174,175] the influence of hydrogen bonding between the phosphorus lone pair and

the acidic proton at C(23) should be taken into consideration. Such an interaction would also

explain the coupling constant observed in 1H-NMR of JPH= 4.5 Hz. Interestingly the chemical

shift of the acidic proton on C(23) at δ 5.26 ppm, is shifted downfield in comparison to the

chemical shift of the corresponding proton in 28 at δ 4.87 ppm. This implies, that although

the hydrogen bonding between P(1) and the acidic proton on C(23) might lead to a higher

electron density at the hydrogen, the weakening of the bond between the proton and C(23),

due to the interaction with the posphine, is strong enough to leave the proton more exposed

to the magnetic field causing the downfield shift. Another explanation could be the differing

position of that particular proton towards the ferrocene and therefore its exposure to the fer-

rocene’s ring current. As, in solution, dynamic behaviour of the thioacetal is expected, one

could expect this influence to be neglect-able, unless the thioacetal position is fixed due to

the suggested hydrogen bond interaction. This type of interaction may facilitate the already

facile lithiation of the thioacetal by stabilising the lithiated species due to interactions between

the lithium cation and the phosphine lone-pair. Still, the high sterical demand at the reactive

centre may cause difficulties in an attempt to couple two ferrocenyl thioacetals over a silane

moiety, as has been demonstrated by further experiments (vide infra).

Due to the low overall yield of the synthesis of the thioacetal 25, experiments that would allow

the synthesis of a PSiP-Pigiphos derivative were first tested using ferrocenyl dithiane 29. Two

equivalents of lithiated ferrocenyl dithiane 29 were allowed to react with one equivalent of

dichlorodimethylsilane yielding the silylated dithiane 28 and starting material in a 1:1 ratio.

As the reaction might occur in an SN 2 like fashion, this is not surprising, since a second substi-

28


tution of the silicon moiety would be hindered due to the sterically very demanding transition

state necessary for the formation of the desired product (cf. Scheme 34). In order to force a

FeSi

S S

ClFe

SS

‡

Fe

HSS

21. 2 equiv n-BuLi

2. 1 equiv SiMe2Cl2Fe

SiSS

Fe

HSS

Cl +

sterically hindered transition state

29 28 29

Scheme 34: Reaction of dithiane 29 n- BuLi and dichlorodimethylsilane and the suggested sterically

hindered transition state for the SN 2-reaction of chlorosilane 28 with dithiane 29.

second substitution of the silyl dithiane 28, several experiments were performed. Cleavage of

the dithiane to give the carbonyl was attempted to reduce the steric crowding around silicon.

Although compound 28 showed high stability and was even stable in contact with water, the

conditions used for thioacetal cleaveage[176] would most probably lead to a reaction at the

resulting highly electrophilic silicon centre. Nonetheless, attempts to deprotect the intermedi-

ate were performed using the milder conditions reported by Soderquist et al..[177] Even under

these conditions, decomposition of the deprotected product was observed.

Aside from the thioacetal cleavage, forcing an SN 1 type mechanism may be another option

to induce the second substitution at the silicon moiety. Because of the high Lewis acidity of

silicon, if a halogen scavenger can generate an even slight concentration of a corresponding

silylenium, even the sterically demanding lithiated dithiane 29 could react. However, reaction

with silver bis(triflimide) led to oxidation of the ferrocene moiety to ferrocenium characterised

by the deep blue colour of the resulting reaction mixture. The 1,3-propanedithiol moiety also

appeared to have been cleaved under these conditions, as the resulting reaction mixture pos-

29


sessed a strong garlicky stench. Using sodium BArF as halogen scavenger lead to a mixture

of several compounds, which could not be completely separated. 29Si-1H-HMBC-NMR showed

two silicon species within a small fraction separated by silica flash column chromatography.

Neither of these could by isolated or fully characterised. The other fractions collected con-

tained a diverse mixture of compounds, resulting from decomposition of the starting material.

Due to the difficulties described and the foreseeable increase of difficulties for compound 25

resulting from the even higher steric demand of the ortho diphenyl phosphine group, further

attempts towards the double substitution of the silicon moiety were abandoned in favour of

further study of silyl substituted derivatives of 25 (vide infra), and the investigation of PSiP-

pincer ligands (cf. chapter 3).

2.3.4 Synthesis and characterisation of PSi derivatives of dithiane 26

Since double substitution of the silicon moiety was unsuccessful, the remaining phos-

phino dithiane 25 synthesised was used for preliminary studies of bidentate PSi ligands. The

chlorodimethylsilyl derivative 30, as well as the dimethylsilyl derivative 2, were produced by

quenching lithiated dithiane 25 with the appropriate chlorosilane (cf. Scheme 35).

Fe

HS S

PPh2

n-BuLi

SiCl2Me2

n-BuLi

SiHClMe2Fe

SiCl

S S

PPh2 Fe

SiH

S S

PPh2

<16.8 % 82 %30 25 2

Scheme 35: Synthesis of the PSi ligands 30 and 2

While compound 25 could not be fully converted to compound 30 and the resulting yield

turned out to be quite low, the synthesis of silane 2 worked well and in a satisfactory

yield. Both compounds showed high stability in air and even against moisture, which is

particularly surprising in the case of the chlorosilane 30. It seems that the steric hindrance

to the accessibility of the silicon moiety paired with the relatively high electron density at

the silicon centre reduces its Lewis acidity to a point at which it is almost inert towards

water. The proximity of the phosphine to the silicon moiety seems to cause an interaction

between the two hetero atoms. This can be seen by 29Si-NMR in which a significant upfield

30


shift of ∆δ –14.0 ppm is observed, when comparing the chlorosilane 28 (δ 23.9 ppm) and

the phosphine bearing derivative 30 (δ 9.9 ppm) to each other. In case of the silane 2, a

coupling between the P-atom and one of the methyl groups bound to the silicon is observed

in 31P,1H-HMBC-NMR, providing evidence of a phosphine–silane interaction.

Out of a number of complexation experiments, only treatment of the silane 2 with [Pt(PPh3)4]

in C6D6 at rt led to an identifiable product formed by Si–H activation. This process seems

to occur similarly to the Si–H activation of the (ortho-phosphinophenyl)silane 31 with

Pt(0) as reported by Takaya et al.[178] Takaya et al. report the formation of a complex

with trigonal-bipyramidal geometry, with an additional PPh3 coordinated to the platinum

moiety as well as the hydride and the PSiP-ligand. This complex seems to be formed via a

square-pyramidal intermediate, which is observable during the first 4 h of the reaction but is

subsequently condumed (cf. Scheme 36).

PSi

P PPh2H MePh2 Pt(PPh3)4

3 PPh3

PtPPh3P

H Si

PPh2

Me

Ph2

isomerisation

rtPtH Si

P

PPh3Me

31

Scheme 36: Formation mechanism of the PSiP-platinum complex of 31 reported by Takaya et al.[178]

(the phenyl groups at the PSiP ligand in the product are omitted for simplicity)

In case of the formation of the Pt-2-complex, no intermediate was observed by NMR, of

course the fact that 2 is a bidentate ligand should facilitate the coordination and reaction

at the metal centre. The product would, therefore, form by coordination of the phosphine

moiety to Pt(0), followed by formation of an η2 bond with the sigma orbital of the Si–H bond,

which then leads to Si–H activation, resulting in a square planar cis-Pt(II)-2-complex with the

coordination site trans to the silyl-donor occupied by triphenylphosphine (cf. Scheme 37).

Structural hypotheses are based solely on NMR experiments. In 31P{1H}-NMR two phosphorus

signals, with the same intensity, showing platinum satellites were observed among signals for

free triphenylphosphine, 2 and Ph3PO. Together with the observation of a hydride signal in

the 1H-NMR spectrum, this suggests a square planar Pt(II) species. The small 31P–31P coupling

constant (JPP=15.7 Hz) is an indication of the cis orientation of the two phosphine ligands.

A further indicator of cis configuration is the magnitude of the Pt–P coupling constant, which

31


Fe

SiSS

HPPtLn

Fe

SiSS

HP PtLn

Fe

SiSS

HP Pt

PPh3

L = PPh3

Scheme 37: Suggested formation path of Pt(II)-2-complex.

has been shown to decrease with increasing trans influence of the adjacent ligand.[179] The

coupling constants of the two phosphines in the Pt(II)-2 complex differ significantly and are

comparable to the data reported by Chan et al.[180] Chan et al. report coupling values for

the phosphine trans to the hydride between 2512 – 2716 Hz, while coupling constants for the

phosphine trans to the silyl donor are much lower at 1280 – 2055 Hz.

5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 ppm

0

5

10

15

20

25

30

35

ppm

PtHSi(CH3)2CHCp CHCp

PPh2 on 2

Ph3PO

coordinated PPh3

Figure 3: 1H–31P-HMBC spectrum (delay set for J= 8 Hz) of Pt(II)-2 complex.

32


Therefore, it seems that the 31P-NMR signal at δ 30.4 ppm with JPtP= 1560 Hz corresponds to

the phosphine trans to the silyl group, while the signal at δ 14.1 ppm with a coupling constant

JPtP= 2487 Hz corresponds to the phosphine trans to the hydride. The signal at δ 14.1 ppm

can thus be assigned to the phosphine in ligand 2. This was confirmed by 1H–31P-HMBC,

which shows a correlation between that phosphorous centre and the ferrocene protons (cf.

Figure 3). There is also a clear correlation observed between the methyl groups on the silicon

and the triphenylphosphine, as well as between the hydride and the two phosphines.29Si–195Pt coupling extracted from the 29Si-INEPT-NMR spectrum has a value of JSiPt=1114 Hz,

which is comparable to values for similar complexes found in literature.[138] In the 1H-NMR,

a coupling to 195Pt was found for the hydride, as well as the methyl groups on the silicon

(JPtH= 1065 and 40 Hz, respectively). In order to measure the 195Pt-NMR shift, a 1H–195Pt-

HMQC was run with a delay adjusted to the coupling of the hydride to the platinum of

JPtH= 1065 Hz. The platinum shift was found to be at δ –5235 ppm showing correlation to

the hydride and the methyl groups on silicon (cf. Figure 4).

-0.50.00.51.01.52.0 -1.5 -2.0 -2.5 -3.0 -3.5 -4.0 ppm

-5400

-5380

-5360

-5340

-5320

-5300

-5280

-5260

-5240

-5220

-5200

-5180

-5160

-5140

-5120

-5100

-5080

-5060

-1.0

ppm

A

A

A

A

A

A

A

AB B

B BB B

B B

A: 195Pt–hydride cross-peaks B: 195Pt–Si(CH3)2 cross-peaks

Figure 4: 1H–195Pt-HMQC spectrum (delay set fot J= 1065 Hz) of Pt(II)-2 complex.

33


2.4 Summary

The synthesis of a PSiP-Pigiphos ligand 1 was investigated following two general approaches.

Although the synthesis of the tridentate ligand was unsuccessful, a synthetic route to an

asymmetric ferrocenyl PSi-ligand 2 was established. This ligand underwent Si–H activation

with [Pt(PPh3)4] to form a square-planar hydrido-triphenylphosphino-2-platinum(II) com-

plex. This complex is of interest for further investigations concerning its catalytic activity

as well as ligand exchange mechanisms. Due to the failure of the attempted PSiP-Pigiphos 1

synthesis, an approach towards a different kind of PSiP-pincer became a matter of interest (cf.

Chapter 3).

34

3 Synthetic approaches towards a chiral PSiP-Pincer ligand

3.1 Introduction

Since major difficulties were encountered in the synthesis of a PSiP-Pigiphos ligand (cf. chapter

2), a simpler molecular structure became a matter of interest. Because the bulk of the prob-

lems were primarily related to the carbon spacer between the ferrocene and the silicon moiety,

exclusion of the spacer resulting from direct silylation of the ferrocene moieties should there-

fore alleviate the problems encountered in the PSiP-Pigiphos synthesis. This would result in a

PSiP pincer-like ligand, that would form a five membered metallacycle upon Si–H activation.

Such a ligand should fullfill the requirements that were already set out for the PSiP-Pigiphos

and therefore, represent the first chiral PSiP-pincer ligand.

3.1.1 Pincer ligands

Ever since the first synthesis of a pincer type ligand by Moulton and Shaw,[181] this platform

has been of great interest. Whereas pincer complexes of the ECE-type (cf. Scheme 38) bearing

a central aryl ring, which interacts with the metal centre via its anionic Cipso atom,[181–186] were

of interest during the first twenty years of pincer ligand chemistry, today a much larger variety

of pincer ligands are known. The great variety of pincer ligand systems is due to diversity of

applicable ligand backbones.[185,187–189]

E

E

E

E

M X

E = NR2, PR2, SRM = Ni, Pd, Pt, Rh, Ir, Sn

Scheme 38: Generalised structure of ECE-pincer ligands and their complexes as first reported by Shaw

and co-workers[181,182] and van Koten et al.[183,184]

The pincer ligand platform has several defining characteristics. Pincer ligands are tridentate

ligands, which form κ3 complexes around a metal centre and contain two metallacycles. They

bear two lateral donor atoms and a central carbon that forms an ipso-carbon-metal bond upon

complex formation, usually through C–H activation.[190] As a consequence of these features,

35


the resulting pincer complexes are highly stable. It has been reported by Shaw[191,192] that the

introduction of two five-membered metallacycles also increases the thermodynamic stability

of these systems. It is the high thermal stability paired with the high reactivity, that arises

from the strong σ-donor effect of the ipso-carbon, which make pincer complexes attractive

for use in catalysis.[193] Pincer complexes have shown a variety of applications not only in

catalysis,[188,194–197] but also as chemical sensors and chemical switches.[187]

3.1.2 Pincer-like PSiP-ligands

Today the term pincer-like ligand is often used to designate ligands with similar features

as actual pincer ligands. They include tridentate complexes with carbene centres or even

nitrogen instead of carbanions.[198] Among these alternative ‘pincer’ ligands/complexes the

PSiP-pincer like ligands are probably the closest example to the original pincer ligands.

Although transition metal-silicon chemistry is well-known[125][199] only a few examples of

silyl donors in a framework of ancillary ligands have been reported.[133,134,200] The first

syntheses of pincer-like NSiN-ligands and their complexes have been performed by Tilley and

co-workers,[142–144] while the Turculet group has claimed the first synthesis of a pincer-like

PSiP ligand.[132] Since then, there have been a remarkable number of publications concerning

the complexes of this PSiP pincer-like ligand and their chemical properties as well as their

catalytic use.[132,140,201] The ready accessibility of coordinatively unsaturated metal com-

plexes[202] or even electron deficient late transition metal complexes[140] of the PSiP-ligand

(cf. Scheme 39) is a direct consequence of the strong trans influence of the silyl donors (cf.

Chapter 2.1.2) introduced into the pincer framework.

Cy2PSiMe

Cy2PRu N

SiMe3

SiMe3

Si

PCy2

PCy2

MMeH

Cl

M = Rh, Ir

Scheme 39: Coordinatively unsaturated and electron deficient pincer-like PSiP complexes reported by

Turculet and co-workers.[140,202]

36

3.2 Synthetic strategy


The synthesis of an asymmetric pincer-like ferrocenyl based PSiP ligand 3 is the main goal

of this project. A secondary objective of the project was the synthesis of a structurally

analogous PPP ligand 4 to allow for comparative studies of the PSiP pincer-like ligand as well

as PigiPhos (cf. Scheme 40). Because of the five membered metallacycles, which are formed

by complexation, the central phosphorus donor atom is expected to be closer to the metal

centre. This should lead to a distinctive trans influence and, therefore, the resulting Ni(II)-PPP

complex should show comparable reactivity to the PSiP-Pigiphos analogue 32 described in

Chapter 2.1.3. Although the synthesis of 4 has been reported by Butler,[203] only the racemate

was isolated and no complex chemistry has been done with this type of ligand to date.

Fe

FeSi

P PH

R

Ph2Ph2Fe

FeP

P P

Ph

Ph2Ph2

R = Me, Ph3 4

Scheme 40: Proposed asymmetric pincer-like PSiP ligand 3 and its PPP analogue 4.

3.2 Synthetic strategy

In order to introduce planar chirality at the ferrocene moieties during the synthesis of the

PSiP-pincer like ligand 3 the sulfoxide route described by Kagan and co-workers[75] was chosen

(cf. Paragraph 1.1.2.2). Starting from ferrocene the chiral p-tolyl-ferrocenyl-sulfoxide 16 is

easily synthesised as reported by Ribière et al.[204] Selective ortho-lithiation then should yield

either the phosphine 33 or the silane 34 as needed. In a second step, the sulfoxide can be

substituted by another electrophile using t-BuLi (cf. Scheme 41).

An analogous route should yield the corresponding PPP analogues 4. As double lithiation of a

37


Fe

FeSi

P PH

R

Ph2Ph2

Fe

S p-tol

O

1. LDA2. ClPPh23. BH3-THF

Fe

S p-tol

OPPh2H3B

Fe

S p-tol

O

1. LDA2. RHSiCl2 Fe

FeSiH

S Stoltol

OO

R

1. t-BuLi2. RHSiCl23. NEt3

1. t-BuLi2. RHSiCl2

Fe

FeSiH

P PPh2Ph2

R

R = Me, Ph

34

35

3

3

Scheme 41: Proposed synthetic routes towards the PSiP-pincer like ligand 3.

molecule would be necessary in order to obtain (SFc,SFc)-3 or (RFc,RFc)-4 the convergent route

yielding the opposite enantiomers should be more feasible.

3.3 Synthetic challenges

3.3.1 Synthetic approach towards the PSiP-pincer like ligand 3

The synthetic approach towards the borane protected phosphine 33 as described by Riant

et al.[75] was reproduced without any problems in a reasonable yield. Problems were not

faced until the attempt of double substitution of dichloromethylsilane in the second step,

which yielded none of the desired material. Reaction of the deprotected phosphine sulfoxide

also failed to yield the desired product upon lithiation with t-BuLi and subsequent quenching

with dichloromethyl silane. Approaching the target compound by first double substituting the

silicon moiety gave the bis sulfoxosilane 34 in a 30 % yield. While the second substitution gave

only minimal amounts of what could be considered to be the target compound, considering31P-NMR (δ –18.5 and –19.71) and MALDI-MS (m/z calcd: 783.12 found: 784.12 [M+H+]).

Several attempts of optimising reaction conditions (temperature, solvents, reaction time) were

unsuccessful, despite the scale of the reaction, only amounts suitable for NMR analysis could

be isolated. Therefore other approaches had to be taken into consideration (cf. Chapter 3.3.3).

38

3.3 Synthetic challenges

3.3.2 Synthetic approach towards the PPP-pincer analogue 4

Similarly to the synthesis of the PSiP-pincer like ligand, 3, two approaches were fol-

lowed. In the first approach, the ferrocenyl sulfoxide 16 was first substituted by using

chlorodiphenylphosphine and subsequently protected with borane. The resulting phos-

phinoferrocenyl sulfoxide 33 was then reacted with one equivalent of t-BuLi and half an

equivalent of dichlorophenylphosphine. As was observed during the synthesis of 3 (vide

supra), this approach failed to yield the desired product. Coupling the ferrocenes over the

phenylphosphine moiety in the first reaction step, gave a low yield of about 18 % in inital

efforts. The second step led to only trace amounts of the target material in a product mixture.

The product was identified in the mixture by ESI-HRMS (calcd: 846.1198, found: 846.1254

[M+]), encouraging further effort in the improvement of the synthesis. Stepwise lithiation of

the bissulfoxophosphine 5 was attempted in order to avoid a route over a double anion (cf.

Scheme 42).

Fe

FeP

P

Ph

Ph2Fe

FeP

S Stoltol

OO

Ph

1. t-BuLi2. ClPPh2 S

tolO

1. t-BuLi2. ClPPh2 Fe

FeP

P

Ph

Ph2PPh2

5 4

Scheme 42: Proposed stepwise lithiation of 5.

Initial efforts to develope a one-pot reaction lead to the formation of a mixture of phosphines.

Introduction of a work-up and filtration over silica in DCM after the first lithiation increased

the yield of the desired final product to an NMR-detectable amount. Seperation by flash

column chromatography gave a mixture of three major compounds, as shown by HPLC

(OD-H, n-hexane/i-PrOH 95:5, 0.7 ml/min, tR: 8.05, 8.47, 8.72 min). As further attempts at

purification were unsuccessful, preparative HPLC was used to further separate the mixtures

under the optimised conditions determined by analytical HPLC (vide supra). These efforts led

to a slightly better but still incomplete seperation. Three fractions were collected, of which

the second (tR: 7.88 – 8.49 min) contained the majority of the desired product, which was

fully characterised. One of the side products separated, could also be characterised and was

found to be diphosphine 35 (cf. Scheme 43).

39


Fe

FeP

P

Ph

Ph2PPh2 Fe

Fe

P

P

Ph

Ph2

4 36

Scheme 43: Products characterised after preperatory HPLC separation.

3.3.3 Explanation for the synthetic difficulties

A closer look at the synthetic difficulties encountered during the synthesis of the PSiP pincer-

like ligand 3 and its PPP analogue 4 reveals that particular reaction steps turn out to cause

major difficulties. Firstly any reaction involving the coupling of the ferrocenes via a central

moiety gives low yields. If the coupling is carried out in the same step as the cleavage of the

sulfoxide no desired product could be isolated (cf. Table 4).

As in the case of coupling over a phosphine moiety, various 31P-NMR signals corresponding to

phosphine oxides were found, the conclusion seemed preeminent, that an oxide transfer from

the sulfoxide to the electrophile takes place. Interestingly, the free t-butyl-p-tolyl sulfoxide

formed during the sulfoxide cleavage seems to perform the oxidation more efficiently than the

bound sulfoxide leading to no product. Therefore it can be assumed, that t-butyl-p-tolyl sul-

foxide might also play a role in the substitution reaction forming the bisferrocenyl species 34

and 5, thus lowering the yields further. These observations serve to emphasise that a direct

synthesis of the PSiP pincer-like 3 and its PPP analogue 4 from the sulfoxide precursors could

not be achieved satisfactorily. As a consequence the synthesis of an inert building block was

investigated (cf. Chapter 5.3).

3.4 The sulfoxophosphine ligand 5

3.4.1 Structure discussion

Over the course of the synthetic route towards the PPP ligand 4 the SPS compound 5 was syn-

thesised as an intermediate in yields up to 45 %. Compound 5 showed interesting features in

40


Fe

FeR''E

Fe

FeR''E

P PPh

PhPhPhS S

toltolOO

LiR'ECl2R''Fe

R

Stol

Oor

E = SiH, PR = PPh2, H

R' = t-Bu, i-Pr2NR'' = Me, Ph

E R′′ R R′ yield [%]

Si–H Me PPh2 t-Bu 0

Si–H Me H i-Pr2N 16 – 33

P Ph PPh2 t-Bu 0

P Ph H i-Pr2N 18 – 45

Table 4: Generalised scheme for the coupling step in the synthesis of 3 and 4 and the yields corre-

sponding to the respective reactions.

1H-NMR. As the epimerisation barrier for phosphines usually lies around 30 kcal/mol[205,206] 5

may be described most strictly as a C1 symmetric molecule at rt, therefore the hydrogen atoms

corresponding to each other on the ferrocenyl and tolyl groups are diastereotopic, hence the

different chemical shifts. The large difference in the chemical shifts of the two Cp′ rings with

a ∆δ of 0.72 ppm is remarkable. Although this observation seemed quite astonishing at first,

X-ray structure determination of crystals grown from DCM/n-hexane gave rise to a possible

explanation for this strong shift (cf. Figure 5).

The tolyl group on S(1) is oriented in such a way, that the aryl ring lies 3.49 Å away from

the next Cp′ carbon bound to Fe(1), facing the Cp′ with the ring plane of the tolyl group.

This T-shaped orientation to each other may be due to a π–π interaction. Therefore, it can

be assumed that a similar conformation is predominantly present in solution and the ring

current of the tolyl group enhances the field at the Cp′ hydrogens leading to the upfield

shift of about ∆δ 0.72 ppm observed in 1H-NMR. The aryl ring on S(2) is oriented in nearly

the opposite direction with regards to the ferrocene moiety (cf. Table 5), comparable to the

reported structure of p-tolylferrocenyl sulfoxide.[207] As a consequence the S(2)-aryl lies face

to face with the phenyl ring on P(1) in an almost parallel fashion (angle between ring planes

is 5.87°) at a distance around 3.8 Å, implying that a parallel-displaced π–π-interaction is

present.[208]

41


P1 C2

C1

S1

O1 C11

C35

C19

C18

O2

S2

C28

Fe2

Fe1

Figure 5: X-ray crystal structure of the SPS-ligand 5.

dihedral Angle [°] dihedral Angle [°]

C(11)–S(1)–C(1)–C(2) –115.8(2) C(28)–S(2)–C(18)–C(19) 89.8(2)

O(1)–S(1)–C(1)–C(2) 132.67(19) O(2)–S(2)–C(18)–C(19) –21.0(2)

C(35)–P(1)–C(2)–C(1) 163.07(19) C(35)–P(1)–C(19)–C(18) –75.3(2)

Table 5: Selection of dihedral angles of compound 5.

The S(1)tolyl facing the Cp′ on Fe(1) also has a significant impact on the C(1)–S(1)–C(11)

angle which is widened by about 5° in comparison to the C(18)–S(2)–C(28) angle, while the

O–S–Fc angle is conversely widened around the S(2) moiety (cf. Table 6).

Angle [°] Angle [°]

C(1)–S(1)–C(11) 104.24(10) C(18)–S(2)–C(28) 99.42

O(1)–S(1)–C(1) 104.93(11) O(2)–S(2)–C(18) 109.05(10)

O(1)–S(1)–C(11) 106.28(10) O(2)–S(2)–C(28) 106.11(11)

Table 6: Bond angles around the sulphur atoms of 5.

Although one would expect that bond angles around the phosphorus atom should increase

42


with more sterically demanding groups,[209] compound 5 shows narrower angles around P(1)

than diferrocenylphenylphosphine reported by Houlton et al.[210] except for the angle between

a ferrocenyl substituent and the phenyl substituent (cf. Table 7).

compound 5 diferrocenylphenylphosphine[210]

Angle [°] Angle [°]

C(2)–P(1)–C(19) 98.55(10) C(24)–P–C(35) 100.0(5)

C(2)–P(1)–C(35) 99.30(10) C(35)–P–C(51) 101.0(5)

C(19)–P(1)–C(35) 99.30(10) C(24)–P–C(51) 98.6(5)

Table 7: Comparison of bond angles around the phosphine of compound 5 and diferro-

cenylphenylphosphine.

3.4.2 Complexation Experiments

A variety of experiments were performed in order to prepare complexes of ligand 5. The

focus of the complexation experiements was limited to d8 metals, except for one complexation

experiment using a Pd0 precursor. Most of the complexation reaction products could not be

completely characterised, as only inconclusive 1H-NMR spectra were obtained particularly

in case of the rhodium and iridium complexes. Therefore 31P-NMR and HRMS were used as

indicators for complexation when possible. Evidence of complex formation was found in five

experiments, for which a variety of MS and NMR methods were used (cf. Table 8).

Metal precursor MS 31P-NMR 1H-NMR NOESY X-ray

[(C2H4)2RhCl]2 n.a. × inconclusive n.a. n.a.

[(COD)RhCl]2 × × inconclusive n.a. n.a.

[(COE)2IrCl]2 × × inconclusive n.a. n.a.

[Pd(COD)Cl2] × × × n.a. ×[Pt(COD)Cl2] × × × × n.a.

[Pd2(dba)3] n.a. inconclusive n.a. n.a. n.a.

Table 8: Analytical data available for 5-metal complexes.

Although analytical data for the rhodium complexes is sparse, formation of a complex is

43


clearly indicated by 31P-NMR. A doublet signal at δ 56.5 ppm with a coupling constant JRhP of

170 Hz independent of the precursor used is observed. In order to rule out the possibility that

the doublet observed corresponds to two signals from two different species, the spectrum was

measured using a 300 MHz, 400 Mhz and 500 MHz NMR confirming the coupling. (cf. Figure

6)

54.0 ppm55.056.057.058.0

202.1 MHz 31P{1H} NMR

162.0 MHz 31P{1H} NMR

121.5 MHz 31P NMR

Figure 6: 103Rh –31P-coupling measured at different field strengths.

In addition to the signal showing the Rh–P-coupling, a singlet at δ 26.4 ppm was observed in

case of the rhodium complex synthesised using [Rh(C2H4)2Cl]2 as a precursor. This implies

that a portion of the ligand 5 is only bound over the sulfoxide moieties to rhodium thereby

leaving the phosphorus uncoordinated. If ligand 5 is reacted with [Rh(COD)Cl]2 the singlet

signal is shifted upfield by ∆δ 0.7 ppm. This suggests that some of the precursor’s ligands

might be included in the complex formed, causing differences in chemical shifts. From this

information, the presence of a large variety of complexes from mononuclear to multi nuclear

complex clusters could be possible. MALDI-TOF-HRMS measurements show a single signal

at m/z 859.9564 corresponding to the molecular formula C40H35Fe2O2PRhS2 which would

fit the formula [RhL]+ ion, with L being 5. In case of the reaction of 5 with [Ir(COE)2Cl]2a brown powder was isolated that showed a 31P-NMR shift of δ –4 ppm and a weak signal

44


in MALDI-TOF-HRMS for C80H70Fe4IrO4P2S4, corresponding to [IrL2]+. These were the

only indications of possible complex formation with iridium(I) and ligand 5. Reacting

[Pd(COD)Cl2] with ligand 5 yielded a red powder that showed a 31P-NMR shift at δ 44 ppm.

(In the 1H-NMR significant chemical shifts for the protons close to the metal moiety could be

observed as well as line broadening. Some signals are more strongly affected than others in

terms of those two parameters.) MALDI-TOF-HRMS showed a weak signal at 859.9561, which

corresponds to [PdL]+. Attempts to synthesis a Pd(0) complex by reacting [Pd(dba)] with

ligand 5 gave inconclusive results in 31P{1H}-NMR, which showed two very broad signals at

δ 28.3 and 26.6 ppm. A platinum(II) complex of 5 was synthesised by dissolving the ligand

in DCM with [Pt(COD)Cl2] yielding a yellow powder. 31P{1H}-NMR of the compound showed

a peak at δ 21.1 ppm with platinum satellites having a coupling constant of JPP t = 3.7 kHz,

while in MALDI-TOF-HRMS a signal corresponding to [PtLCl2+Na]+ was detected. All of

the complexes mentioned showed poor solubility in ether, toluene or benzene, but they were

moderately soluble in chloroform and THF. They also showed moderate to good solubility

in DCM and pyridine. In order to obtain single crystals, a variety of crystallisation methods

were applied, using different solvent systems. While most attempts resulted in decomposition

of the complexes in solution or precipitation of a powder, crystallisation of [PdLCl2] by gas

phase diffusion of benzene into a THF solution of the complex at –20 ◦C was successful. The

resulting single crystals were of poor quality, preventing refinement of the crystal structure

further than to an R-value of 8.41 %. The low quality of the crystals may be explained by

the high solvent to complex ratio in the crystals and the low crystallisation temperature. Two

molecules of the platinum complex crystallised together with ten benzene molecules and one

THF molecule. In addition to the disorder of the solvent molecules, this might also have lead

to cracks in the crystals due to solvent evaporation during the short period of time the crystals

were at rt. However, a reasonable structural model could be obtained from the solution of the

crystal structure, showing that the phosphine as well as one sulfur moiety coordinate to the

platinum centre, while the other two coordination sites are occupied by two chlorido ligands

(cf. Figure 7).

This structure was also corroborated by 2D-NMR data of the platinum(II) complex. The

NOESY spectrum showed a contact between protons of the tolyl group on S(2) (δ 8.06 ppm)

and protons on the phenyl ring (δ 7.70 ppm; cf. Scheme 44). This contact is only possible if

one sulfoxide is not coordinated to the metal centre, thus allowing it to move freely into a

conformation allowing contact.

The fact that only one sulfur is bound to the metal centre is not surprising, as it is known

45


P1

S1

S2 O1O2

Pd1

Cl2

Cl1

Figure 7: Structure of the dichloropalladium(II) complex of 5.

FePt SCl

O

P

Fe

SOCl

NOE contact

5

Scheme 44: Observed NOE contact in the dichloroplatinum(II) complex of 5.

that sulfoxide bound over the sulfur moiety to the metal have a strong trans labilising

effect.[211–213] Therefore, the only accessible position for the second sulfur moiety, which

lies trans to the other sulfur donor, in case of a square planar coordination around the

metal, is strongly disfavoured. Only coordination by the oxygen atom can be taken into

consideration,[214] but seems unlikely considering the arguments mentioned above. Tem-

perature dependent 1H-NMR of the palladium complex showed, that at 303 K the signals

corresponding to both tolyl groups are close to the fast exchange limit with regard to rotation

around the S–tol bond. Also the phenyl group shows fast exchange with respect to rotation

around the P–Ph bond. When the temperature is decreased, the signals corresponding to the

phenyl protons and the protons on the tolyl group on S(1) (cf. Figure 7) become broader,

46


with the phenyl proton signals coalescing at 223 K, while the protons on the tolyl group on

S(2) remain in fast exchange (cf. Figure 8). Assuming that the chemical shift difference

between the exchanging protons on the corresponding aromatic rings are similar, when

the slow exchange limit is reached, the energy barrier to the rotation is the lowest in case

of the tolyl group on S(2). This implies that the coordination of S(1) and the phospho-

rus to the palladium have an effect on the rotational barrier of the attached aromatic systems.

7.07.58.08.5

223

233

243

253

263

273

283

293

303

ppm

T/KS(1) P(1) S(2) P(1) S(1) S(2)

Figure 8: Temperature dependent 1H-NMR of the dichloropaladium(II) complex of 5.

3.4.3 Catalytic experiments

The complexes of ligand 5 were tested for their catalytic activity in selected reactions. The

rhodium complex of ligand 5, synthesised from [Rh(COD)Cl]2, was tested in Miyaura-Hayashi

reaction following the reaction procedure by Dornan et al.[215] Initial attempts at 40 ◦C gave

high yields (up to 99 %), but negligible enantiomeric excess. At 0 ◦C no product is observed,

however, the best conditions were found to be around room temperature giving 60 % yield

and up to 19 % ee (cf. Table 9). Although the enantiomeric excess achieved is only marginal,

47


it implies that the chiral ligand is somehow involved in the catalytic cycle.

O BOHHO

cat.EtOAc

O

Rha, PhB(OH)2, T, t, yield ee

mol% equiv ◦C h % %

4 4 40 24 99.5 rac

4 4 40 1 40 rac

4 1.5 40 24 95 rac

2 4 40 1 60 rac

4 4 0 24 0 n.a.

4 4 rt 24 14 16

4 4 rt 4 11 15aunder the assumption that the rhodium complex

of ligand 5 has a molecular formula of the type

[C40H35ClFe2O2PRhS2]n

Table 9: Rhodium catalysed Miyaura-Hayashi reaction.[215]

The dichloropalladium complex of 5 was tested in allylic substitution of diphenylallyl acetate

with dimethylmalonate. The isolated complex was used initially, and was synthesised starting

from [Pd(COD)Cl2]. The reaction was performed at 0 ◦C for 4 h yielding 7 % of the desired

product with 82 % ee of the (S) enantiomer. As the isolated dichloropalladium complex

showed such low activity, a catalysis was run with the palladium catalyst generated in situ,

by adding ligand 5 and bis((1,3-diphenlallyl)bromopalladium(II)). Although a higher yield

was achieved (90 %), the main catalytically active species in the reaction mixture seemed

to be the precursor itself, as only a racemic mixture (2 % ee) was isolated. The problems

were overcome by using bis(allylchloropalladium(II)) as precursor to generate the catalyst

in situ with ligand 5. In a first attempt a yield of 97 % at an enantiomeric excess of 77 % ee

was achieved. Change of parameters such as solvent, temperature and base did not show

significant impact on the enantiomeric excess (cf. Table 10). Still further optimisation may be

considered.

48

3.5 Summary

Ph Ph

OAc O

MeO

O

OMe

Pd cat.

N,O–bis(trimethylsilyl)acetamide Ph Ph

O

OMe

O

MeO

Pd, additive T, t, solvent yielda ee

mol% ◦C h % %

5 LiOAc rt 16 AcN 97 77

5 NaOAc rt 16 AcN 99 77

5 KOAc rt 16 AcN 93 78

5 LiOAc rt 16 DCM 95 78

5 LiOAc rt 16 tol 95 74

5 LiOAc rt 16 ether 99 73

10 LiOAc 0 24 AcN 78 74

10 NaOAc 0 24 AcN 76 76adetermined by 1H-NMR, using 1,3,5-Tri-t-

butylbenzene as internal standard.

Table 10: Allylic substitution reaction using the dichloropalladium(II) complex of 5.

3.5 Summary

The synthesis of enantiomerically enriched PSiP (3) and PPP (4) pincer-like ligand was in-

vestigated. Difficulties were encountered due to oxygen transfer from sulfoxide to the elec-

trophiles used in the synthetic route. Nonetheless, an SPS type ligand 5 was synthesised as a

step towards the PPP pincer-like ligand 4. Complexation of the sulfoxophosphine ligand 5 to

palladium and plantinum was demonstrated and the resulting complex was carefully investi-

gated. Evidence of complexation to rhodium was found. The resulting complexes were tested

in asymmetric catalysis and showed moderate to good enantioselectivity.

49


50

4 Biferrocenylsulfoxides and Biferrocenylsulfides

4.1 Introduction

The work towards a chiral PSiP-Pincer ligand and its PPP analogue described in the previous

chapter yielded the SPS-ligand 5 as an intermediate, which itself showed promising features in

catalysis (cf. Chapter 3.4). The ligand 5 formed a two coordinate complex with palladium and

platinum, as the second sulfoxide cannot coordinate over the sulfur moiety to the metal centre

due to the strong trans-labilising effect of sulfur-bound sulfoxides.[211–213] In order to form a

complex involving both sulfoxides, they need to be in a cis arrangement. This requirement can

be satisfied by removing the phosphine as linking moiety between the two ferrocenyl groups

resulting in a bisferrocenyl-disulfoxide (BiFeSO) (cf. Scheme 45).

FeFe

SS

R

OR

O

Scheme 45: Generalised structure of BiFeSO.

4.1.1 Sulfoxide ligands

Chiral sulfoxides have been shown to be fairly stable towards epimerisation, activation en-

thalpies for pyramidal inversion for diaryl and alkyl aryl sulfoxides reported to be ∆H‡=35 –

42 kcal/mol by Rainer et al.[216] (cf. Table 11).

As a consequence, racemisation of enantiopure sulfoxides only takes place at temperatures

around 200 ◦C, well above the decomposition temperature of several sulfoxides such as the

cis-elimination of 1,2-Diphenyl-1-propyl phenyl sulfoxide.[217] Therefore, sulfoxides can be

considerd sufficiently optically stable to be isolated as enantiopure compounds and stored.

Synthetic routes towards enantiomerically pure chiral sulfoxide are manifold[218,219] making

them of high interest for use in stereoselective synthesis. Solladié first reported extensively on

the use of sulfoxides as chiral auxiliaries in asymmetric synthesis in 1981[220] following brief

descriptions in earlier reviews.[221,222] Today the use of sulfoxides as chiral auxiliaries is well

established.[223]

51


p-tolSOR

RSOp-tol

∆H‡, ∆S‡, Ea, log A,

R kcalmol

kcalmol·K

kcalmol

sec−1

2,4,6-(CH3)3C6H2 35.4 1.3 36.3 13.7

2-CH3C6H4 36.6 –2.8 37.5 12.8

C6H5 36.2 –5.1 37.2 12.3

1-Adamantyl 42.0 3.8 43.0 14.3

CH3 37.4 –8.0 38.4 11.7

Table 11: Activation parameters for the racemisation of p-tol–SO–R in p-xylene.[216]

Another field of application for enantiomerically pure sulfoxides is in the synthesis of ligands

that are potentially useful in asymmetric catalysis. In 1976, James et al. reported the first

asymmetric catalysis employing a chiral sulfoxide.[224] Inspired by known DMSO complexes,

that showed activity in hydrogenation reactions they synthesised the ruthenium complexes

fac-[RuCl3(R′R′′SO)3]− and cis-[RuCl2(R

′R′′SO)4] using different racemic sulfoxides and were

able to prove their activity in olefin activation for some substrates. The only enantiomerically

pure complex with respect to the sulfur moiety they were able to isolate was [RuCl2(MeSOp-

tol)3], which failed to give any enantiomeric excess in hydrogenation reactions. Ironically,

a succesful asymmetric hydrogenation was achieved with a sulfoxide ligand bearing a chiral

centre at one of the alkyl groups, namely iso-pentane. Using that ligand they achieved an

enantiomeric excess of 12 % ee. A year later, inspired by the DIOP ligand reported by Kagan

and Dang,[225] James and McMillan reported the synthesis of DIOS, BDIOS and DDIOS from the

known dithiol 36 (cf. Scheme 46). Based on those ligands, James and McMillan synthesised

a variety of complexes, of which [RuCl2(DIOS)(DDIOS)] gave the best results with regard to

enantiomeric excess, delivering a value of 25 % ee (cf. Scheme 47).[224,226]

Later approaches towards catalytic hydrogenation relied mainly on non C2 symmetric biden-

tate ligands containing a heteroatom as the second donor, with the reported enantiomeric

excesses ranging from 0 – 75 % ee.[227–229] Of these examples, the work on iridium-catalysed

transfer hydrogenation by van Leeuwen’s group is particularly interesting, as it shows the im-

pact of the chiral centre at the sulfoxide on the enantiomeric excess of the product (cf. Table

12).[229]

52

4.1 Introduction

O

OMeMe

CH2SH

CH2SHH

H

1. MeI, NaOH2. H2O2

O

OMeMe

CH2SOMe

CH2SOMeH

H36

1. BnBr, NaOH2. H2O2

H2O, H+

DIOS

O

OMeMe

CH2SOBn

CH2SOBnH

H

O

OMeMe

CH2SOMe

CH2SOMeH

H

BDIOS DDIOS

Scheme 46: Synthesis of DIOS and its derivatives from dithiol 36.[224,226]

O

OHO

HO2.6mol% [RuCl2(DIOS)(DDIOS)

H2 44psi, 55°C, 168h

O

OHO

HO

49%, 25%ee

Scheme 47: Asymmetric hydrogenation of itaconic acid using [RuCl2(DIOS)(DDIOS)] by James and

McMillan.[224,226]

During the 1990s, most work published on sulfoxide containing ligands in asymmetric catal-

ysis utilised ligands containing at least one additional heteroatom donor. Their application in

asymmetric catalysis has been complemented by catalytic Diels-Alder-reaction, allylic substitu-

tion and diethylzinc addition to benzaldehyde (for further details cf. the review by Fernández

and Khiar[218] and references therein). During that time, publications on asymmetric catalysis

with "pure" bis-sulfoxide ligands appeared sporadically. Nonetheless, the first asymmetric, cat-

alytic Diels-Alder reaction using a sulfoxide ligand was among them.[230] The ligands used by

Khiar et al. are readily accessible from the known (R)-methyl p-tolyl sulfoxide and commer-

cially available (S)menthyl p-toluenesulfinate in a one- ((S,S)-bis-p-tolylsulfinylmethane 37)

and three-step ((S,S)-bis-p-tolylsulfinylpropane 38) reactions, respectively (cf. Scheme 48).

53


O OHIr(I), ligand

HCO2H

S NH2BnO

OH

S NH2Bn

O

OH

conv., % ee, % conv., % ee, %

99 65 (S) 56 27 (R)

Table 12: Enantioselective transferhydrogenation with a chiral sulfoxide ligand by van Leeuwen and

co-workers.[229]

S

O

p-tol

1. LDA, THF, –78°C

2.

S

O

p-tol O-menthyl

SSH H

p-tolp-tol

OO

38

1. 2.2 equiv LDA

2. 2.2 MeI

SSp-tolp-tol

OO

Me

1. 1.5 equiv KHMDS

2. 2.2 MeISS

Me Mep-tol

p-tol

OO

39

Scheme 48: Bis-sulfoxide ligand by Khiar and Fernández.[230]

Khiar et al. suggested that the iron(III) moiety in their catalyst would be bound to the oxygen

lone-pairs of the sulfoxides, due to the hard nature of the metal centre. Their catalytic system

showed a endo:exo ratio up to 96:4, with an enantiomeric excess of the endo-(S) product of

56 % ee for the Diels-Alder reaction of 3-acryloyl-1,3-oxazolidin-2-one with cyclopentadiene

(cf. Table 13).

Another example is given in the work of Tokunoh et al. using (S,S)-1,2-bis(p-

tolylsulfinyl)benzene (BTSB) as a ligand. Their ligand showed a moderate induction in allylic

substitution of up to 64 % ee with palladium(II).

Recently, interest in C2-symmetric bis-sulfoxide ligands for asymmetric catalysis has grown sig-

nificantly and the performance of new catalytic systems including bis-sulfoxides has reached

54

4.1 Introduction

NO

O OFeI3L

COR

H

H

COR

COR

H

H

COR

endo

exo

(R)

(R)

(S)

(S)

ligand L yield, % endo:exo (S):(R)

37 74 95:5 68:32

38 78 96:4 78:22

Table 13: Stereoselective Diels-Alder reaction with a bis-sulfoxide ligand by Khiar et al.[230]

enantiomeric excesses that are comparable to those of known catalytic systems.[231–241] In

2008, Dorta’s group found that C2 atropisomeric sulfoxides showed competitive performance

in Rh-catalyzed 1,4-addition of arylboronic acids to cyclohexenones, reaching up to 98 % ee

and 99 % yield.[233] Their so called BINASO ligand, a 1,1’-binaphtyl derivative similar to Noy-

ori’s BINAP,[242] can be synthesised in a single reaction starting from commercially available

materials (cf. Scheme 49). The resulting diastereomeric mixture can easily be separated by

column chromatography, giving ready access to all four diastereoisomers of p-tol-BINASO.

One year later, Dorta an co-workers presented a similar catalytic system using

dimethylbiphenyl-2,2’-diyl-bis(p-tolylsulfoxide) (p-tol-Me-BIPHESO; cf. Scheme 49) that

showed even higher selectivity in 1,4-additions, with an enantiomeric excess of 99 % ee at

98 % yield.[236] Similar work has subsequently been published on rhodium catalysed 1,4-

additions using a variety of different C2-symmetric bis-sulfoxides as ligands by the groups of

Zhou and Li,[237] Liao[238,239] as well as Khiar and Fernández[240] (cf. Scheme 50).

In addition to the reports of catalytically active rhodium complexes, there have only been a few

examples of bis-sulfoxide late-transition-metal catalysts in the recent years. One is the macro-

lactonisation via hydrocarbon oxidation reported by White and co-workers, using among other

sulfoxides[243,244] (rac)-1,2-bis-(phenylsulfoxy)ethane together with palladium(II)acetate as a

precursor to achieve the macrocyclisation with high chemo-[244] and regioselectivity.[245] The

system proved effective enough to be used for the total synthesis of 6-deoxyerythronolide B

55


BrBr

1. Li base; –78°C

2. (1R or 1S)-menthyl- (S or R)-p-tolyl- sulfinate, –78°C – rt

S

SO

p-tol

O

p-tolS

SO

p-tol

O

p-tol

(Sa)-BINASO-diastereoisomers

(Ra)-BINASO-diastereoisomers

BrBr

1. Mg0, toluene/THF (2:1), reflux

2. (1R or 1S )-menthyl- (S or R )-p-tolyl-sulfinate, –40°C

S

SOO

p-tol

p-tolS

SOO

p-tol

p-tol

(Sa)-BIPHESO-diastereoisomers

(Ra)-BIPHESO-diastereoisomers

Scheme 49: Syntheses of BINASO and BIPHESO ligands.[233,236]

in the second to last reaction step.[246] The other example of late-transition-metal catalysis

using bis-sulfoxide ligands was very recently reported in a paper by Dorta’s group. They used

BINASO-platinum(II) complexes in hydroboration, giving Markovnikov and Anti-Markovnikov

products in a ratio up to 4:1, and diboration of styrene. However, although they used enan-

tiomerically pure BINASO, they did not observe any enantioselectivity in the formation of the

benzylic stereogenic centre (cf. Scheme 51).[241]

Due to these recent developments in catalysis with bis-sulfoxide ligands, the idea of creating

a BiFeSO ligand as depicted in Scheme 45 seemed very intriguing. This especially because it

would bear a chiral centre at the sulfoxide and have axial chirality like BINASO, presuming

that rotation around the ferrocene–ferrocene bond is hindered, and in addition planar chirality

at the ferrocene moieties.

4.1.2 Known Biferrocenyl compounds

More than thirty years after the first synthesis of biferrocene by Nesmejanowa and Pere-

walowa[247,248] and ten years after the synthesis of BINAP,[242] the syntheses of the first bi-

56

4.1 Introduction

MeOMeO

S

SOO

R'

R'S

SOO

R'

R'

OR

OO

RO

R = CH2, CH2CH2R' = t-Bu, p-tol

Zhou and Li

S

S

OO Fe Fe

S SO O

Liao Khiar and Fernández

Scheme 50: Bissulfoxide ligands used in rhodium catalysed enantioselective 1,4-addition of boronic

acid.[237–240]

OBH

O

OBH

O

or

1. 2mol% Pt-BINASO DCM

2. NaOH/H2O2

OHOH

Markovnikov anti-Markovnikov

OB

O OB

O

1. 2mol% Pt-BINASO THF, rt

2. NaOH/H2O2

OH

rac

OH

Scheme 51: Hydroboration and diboration of styrene reported by Dorta and co-workers.[241]

ferrocenyl ligands were reported.[67,249] Sawamura et al. reported almost simultaneously

the synthesis of 2,2”-bis(diphenylphosphino)-1,1”-biferrocene (BIFEP)[249] and 2,2”-bis[1-

57


(diphenylphosphino)ethyl]-1,1”-biferrocene (TRAP).[67] The BIFEP ligand was synthesised

from (diphenylphosphinyl)ferrocene to give the doubly oxidised BIFEP as a racemate, which

was resolved using dibenzoyltartaric acid before reduction to the enantiomerically pure (S,S)-

and (R,R)-BIFEP ligands (cf. Scheme 52).

Fe

P Ph2

O

i-Pr2NMgBr–THF

Fe

PO

Ph2

MgBr

Ni(0) (in situ)

Fe

P Ph2

O

2

1. resolution

2. HSiCl3,

I2

Fe

P Ph2

O

I

Fe

rac

Fe

Ph2P PPh2

(R,R)- and (S,S)-BIFEP

Scheme 52: BIFEP-synthesis by Sawamura et al.[249]

The coupling to the biferrocene using nickel(0) was reported not to yield any meso-

biferrocene product, but only the two desired enantiomers. Treatment of BIFEP ligands with

PdCl2(CH3CN)2 gave a cis-chelated palladium complex. As they stated, the ligand "does not in-

trinsically have axial chirality,"[249] but they stated a preferred conformation of the correspond-

ing palladium complex. This statement was substantiated by the work of Espino et al., who cal-

culated that the activation energy for the conformational change was ∆G‡= 58±3 kJ ·mol−1

from the major to the minor and ∆G‡= 54±3kJ ·mol−1 from the minor to the major con-

former, on the basis of the ratios of the two atropisomers in temperature dependent NMR,

corresponding to a temperature of about 260 K for the conformational exchange.[250] For the

synthesis of their BIFEP derivatives, they used an approach first described by Xiao et al.,[251]

which starts from an enantiomerically pure 1-iodo-2-(arylsulfinyl)ferrocene, which is coupled

to a biferrocene by an Ullmann coupling. The sulfoxide groups are then substituted with phos-

phines by treatment with t-BuLi and the corresponding electrophile (cf. Scheme 53).

Other than the cis-chelating BIFEP ligands, the TRAP-ligands synthesised by Sawamura et al.

58

4.1 Introduction

Fe

I

SR

O

Fe

Fe

SS

OO

R RCu 1. t-BuLi

2. ClPR'2

Fe

Fe

SR'2P

O

R 1. t-BuLi

2. ClPR''2

Fe

Fe

PR''2R'2P

R = p-tolR' = Ph, 3,5-Me2Ph, 3,5-Me2-4-OMe-PhR'' = Ph, 3,5-Me2Ph, 3,5-(CF3)2Ph

Scheme 53: Modular BIFEP-synthesis as reported by Xiao et al.

from Ugi’s amine showed trans-chelating abilities.[67,68] Surprisingly, the TRAP ligands gave

higher enantiomeric excess in asymmetric hydrogenation than the BIFEP ligands.[252] In order

to close the structural gap between the BIFEP and TRAP ligand families and in analogy to the

Walphos ligands, Zirakzadeh et al. have recently reported the synthesis and application of a

new type of biferrocene ligands as depicted in Scheme 54.[253]

Fe

Fe

PR2R2PFe

Fe

R2P

MeH

Me

PR2

Fe

Fe

PR2R2P

MeH

BIFEP TRAP Walphos-analogue

Scheme 54: The three diphosphino-biferrocene ligand families.

Although Xiao et al. created a synthetic route, which had a (diarylsulfinyl)-biferrocene inter-

mediate (cf. Scheme 53), such a BiFeSO type ligand, as depicted in Scheme 45, has been

neither studied nor purposefully synthesised to date. In this project, a simple two step synthe-

59


sis, starting from ferrocene to a BiFeSO derivative was developed and the structural properties

of the resulting compound were extensively investigated.

4.2 Synthesis and structural features of BiFeSO 6

The simplest possible approach towards a BiFeSO type ligand utilises easily accessible t-butyl-

ferrocenylsulfoxide generated by the reaction of ferrocenyllithium with enantiomerically pure

bis-(t-butyl)-thiosulfinate. The ortho lithiation can be achieved simply by the use of n-BuLi (cf.

Chapter 1.1.2.2). Coupling to the biferrocene was performed following a modification of the

procedure reported by Dong et al.[254,255] Solid CuCN (0.5 equiv) was reacted with lithiated

t-butyl-ferrocenylsulfoxide at –30 ◦C for about 20 min before the reaction mixture was satu-

rated with oxygen at –78 ◦C to give a deeply red solution. Stirring under oxygen atmosphere

over night while allowing the reaction mixture to warm up to rt introduced the desired planar

chirality (cf. Scheme 55).

Fe

SO

n-BuLi

THF, –78°C Fe

SO

Li

1. 0.5 equiv CuCN –30°C

2. O2, –30°C – rtFe

Fe

SSO

O

6

Scheme 55: Synthesis of BiFeSO 6.

Flash column chromatography gave two products showing 1H-NMR signals that correspond

to the suggested structure. The first compound eluted (6a) slowly turned green in solution,

while forming a precipitate. On the other hand, the product that eluted as the last fraction

(6b) seemed to be stable in solution. In order to remove the ferrocenium formed quickly from

the first sample, a DCM solution of 6a was quickly washed with water and then concentrated

in vacuo. The combined yield of both products together was about 60 % with a ratio of 15:1

60

4.2 Synthesis and structural features of BiFeSO 6

6b/6a. This ratio showed large variations due to the difficulty of isolation of compound 6a.

Besides the easy separability of the two compounds by column chromatography, significant

differences in the chemical shifts of the ferrocenyl protons in the 1H-NMR can be observed

(cf. Figure 9). HSQC and HMBC spectra, however, suggest the same connectivity and HRMS

showed the same molecular mass. Due to the fact that a meso-product would lead to a less

symmetric system and therefore to more complex NMR-spectra, this explanation for the oc-

currence of two products with the same connectivity was excluded. Therefore it seems, that

6a and 6b are atropisomers of each other. For compound 6b single crystals suitable for X-

ray diffraction were obtained by crystallisation from DCM/n-pentane. The crystal structure

showed an (Ra) configuration of the axial chirality (cf. Chapter 16). Therefore an (Sa) config-

uration for 6a as depicted in Scheme 56 seems logical.

Fe

S

t-Bu

O

Fe

SFe

S

t-Bu

O

O

t-Bu

Fe

S

O

t-Bu

6a 6b

Scheme 56: The proposed configuration of 6a (left) and the configuration of 6b (right) as determined

by X-ray.

This suggestion also gives an explanation for the appearance of an NMR-signal in the 1H-NMR

spectrum of 6a at δ=7.79 ppm (cf. Figure 9), which implies the presence of acidic protons in

the structure.

As the (Sa)-6 atropisomer (6a) has the sulfoxide groups in vicinity to each other, they could

act as a base, that, similarly to a proton sponge, may trap protons between the sulfur lone-

pair and an oxygen lone-pair forming a six membered ring composed of two sulfoxide groups

bridged over two protons (cf. Scheme 57).

It was possible to demonstrate the acidity of the protons at δ= 7.79 ppm by washing a

DCM solution of (Sa)-6 with degassed aqueous NaOH or 10 % DCl in D2O, both resulting

in the vanishing of the signal in 1H-NMR spectrum. In addition, in the case of the protium-

deuterium exchange a 2H-NMR was measured, showing the appearance of a deuterium signal

61


6a 6b

ppm ppm

Figure 9: 1H-NMR of the ferrocenyl protons of 6a and 6b and the acidic proton of 6a.

HO

SH

O

SFc

Fc

2+

Scheme 57: Suggestion for the protonated form of 6a.

at δ=7.74 ppm. In order to obtain more evidence for the structural nature of 6a and lend

more credence to the concept of two atropisomers, not undergoing conformational exchange,

quantum chemical calculations were performed (cf. Section 4.3).

Both products obtained from the ferrocene coupling were used in attempts to form complexes.

For 6a no clear evidence for a complex formation with diverse Pd(II), Pt(II) and Rh(I) pre-

cursors could be found. It has to be mentioned that the number of complexation experiments

with 6a was also restricted due to the very low isolated yields (<4 %). Coordination of 6b

was attempted to several transition metals (Mo(0), W(0), Ru(II), Os(II), Co(II), Rh(I), Ni(II),

62

4.3 Computational experiments with regard to the rotational barrier of BiFeSO 6

Pd(II), Pt(II), Cu(I), Au(I)), without any success. The reason for the unsuccessful complex-

ation experiments with 6a and 6b are probably of a different nature. In case of 6b the only

explanation that could be given are the weak coordination properties of the molecules sulfox-

ide group. For 6a one would assume that the poor donor properties could be overcome by

the possibility of chelation of the metal, as the sulfur lone pairs are in close proximity to each

other. On the other hand, the accessibility of the coordination centre is probably very low in

comparison to BINASO, as the ferrocene groups enhance steric hindrance within the molecule

significantly.

4.3 Computational experiments with regard to the rotational barrier of

BiFeSO 6

In order to confirm the atropisomers (6a and 6b), quantum chemical calculations were per-

formed to give an estimate of the energy barrier to conformational change. Starting from

the structural data from X-ray crystallography, a relaxed conformation of BiFeSO 6b was first

calculated to give a starting point. Then the energies for different rotations around the dihe-

dral angle C(2)–C(1)–C(15)–C(16) (cf. Scheme 10) were calculated (cf. Section 4.3.1). For

practical reasons the calculated structures of 6 are referred to as conformations.

4.3.1 Computational details1

All equilibrium geometries were optimized using the B3LYP[256–258] and BP86[257,259] density

functional methods employing the Dunning correlation consistent basis sets (Ref) along with

Stuttgart-Köln-MCDHF-RSC-28-ECP pseudo potentials to model the iron atom core electrons.

All calculations were performed with the Gaussian G09 program suite[260]. For the rotation

of the dihedral angle C(2)–C(1)–C(15)–C(16) (φ1) a potential energy surface scan was per-

formed with an incremental rotation angle of 30 degrees (ModRedundant keyword). After

each dihedral angle rotation the structure was allowed to optimize within 20 geometry op-

timization steps. For the calculations/prediction of the magnetic shielding tensors gauge-

including atomic orbitals (GIAO, also know as London orbitals)[261–264] were employed.

4.3.2 Computational results

For the evaluation of the data produced by these calculations the electronic energies calcu-

lated after the last geometry optimisation step were compared to the angle between the two

1Computational details were provided by Oliver Sala, who conducted the calculations.

63


Cp rings (φ2). The energy of the initial structure (φ1=125.1, φ2= 47.9) was defined as ref-

erence point. φ2 is defined to be zero if, when looking along the C(1)–C(15) bond the two

ferrocenes adopt an eclipsed geometry. φ2 increases if the ferrocene closer to the viewer is ro-

tated clockwise along the C(1)–C(15) bond and φ2 decreases if the same ferrocene is rotated

counter-clockwise (cf. Figure 10).

C2

C1C15 C16 47.9°

Figure 10: Atom labels for the dihedral angle and the geometrically optimised structure of 6b with the

angle φ2 of 47.89°.3

It should be mentioned here, that φ2 does not automatically correspond to the dihedral angle

φ1, as the Cp rings may be distorted due to high strain. In case of the scan with increasing φ1

an additional value was taken for φ1= 305.1° after the 13th geometry optimisation step (cf.

Table 14), as it depicts the crucial step, in which the t-butyl groups pass the ferrocenes (cf.

Figure 11).

The incremental change of the dihedral angle was performed in both directions, due to the

asymmetric nature of the molecule. While following the conformational change by increasing

the dihedral angle φ1 gave values for a complete 360.0° rotation around the C(1)–C(15) bond

(cf. Table 14), the results obtained from decreasing φ1 only cover a range of 300.0° (cf. Table

15) as major difficulties were encountered with the calculations from this point on (vide infra).

3atoms in calculated structures are depicted as spheres in order to differentiate from crystal structures.

64


Figure 11: First time the ferrocene groups have to pass by the t-butyl groups in case of increasing φ2.

φ1, [°] φ2, [°] electronic

energy, [kcal/mol]

125.1 47.9 0.0

155.1 24.0 3.6

185.1 –27.3 7.2

215.1 –36.4 12.7

245.1 –49.4 23.9

275.1 –62.6 41.0

305.1a –78.6 59.4

305.1 –130.7 26.1

335.1 –155.9 10.6

365.1 –167.0 13.5

395.1 –183.7 21.3

425.1 –246.6 15.6

455.1 –278.6 15.1

485.1 –297.8 19.0aafter 13 geometry optimisation cycles.

Table 14: Data for incremental increase of φ1.

For the plot of the electronic energy versus φ2 the data of the two scans were consolidated

(cf. Figure 13). On both sides of the starting point at 47.9° a high energy barrier is predicted.

For increasing φ1, i.e. decreasing φ2, the highest energy is reached in the moment, in which

65


φ1, [°] φ2, [°] electronic

energy, [kcal/mol]

125.1 47.9 0.0

95.1 65.6 4.5

65.1 83.9 17.1

35.1 104.8 35.9

5.1 155.7 24.4

–24.9 185.0 22.3

–54.9 198.9 27.1

–84.9 211.4 35.1

–114.9 230.5 40.0

–144.9 249.1 45.1

–174.9 277.4 44.9

Table 15: Data for incremental decrease of φ1.

the t-butyl groups have to pass the ferrocene groups with an energy barrier of 59.4 kcal/mol.

For decreasing φ1, i.e. increasing φ2, the first local maximum in energy at 35.9 kcal/mol is

reached, when the two t-butyl groups have to pass each other. In both directions a local

minimum is reached after the first energy barrier is passed. This is the point at which the

conformation comes closest to the proposed structure of 6a. The relative energies at these

local minima differ largely from each other (10.6 kcal/mol at φ2= –155.9° and 22.3 kcal/mol

at φ2=185.0°), as the t-butylsulfoxy groups are differently oriented in the two molecules due

to the different path in approaching the structure. Geometry optimisations for the proposed

structure of 6a have also been performed resulting in a relative energy difference to 6b of

9.1 kcal/mol (cf. Figure 12). This comes close to the energy of the conformer at φ2= –155.9°,

where the main structural difference to the proposed structure is the different orientation of

one t-butyl group. The different orientation remains while φ1 increases. As a result the final

structure resulting after a 360.0° rotation of φ1 does not correspond to the initial structure

given by 6b (cf. Figure 14) with a difference of the angle between the Cp planes of 14.4° and

a resulting energy difference of 19.0 kcal/mol. A rotation around the S–Cp bond to reach the

initial configuration might be significantly hindered, as at least one of the t-butyl groups would

have to pass the opposing ferrocene to return to its initial conformation.

66


9.1 kcal/mol10.6 kcal/mol 22.3 kcal/mol

Figure 12: Structures of 6 at the second local minimum. middle: geometry optimisation of the pro-

posed structure of 6a. left: local minimum at φ2= –155.9. right: local minimum at φ2=185.0°.

67

4B

iferrocenylsulfoxidesand

Biferrocenylsulfides

-300 -250 -200 -150 -100 -50 0 50 100 150 200 250 300

10

20

30

40

50

60

Φ2 [°]

Eel

[kca

l/mol

]

Figure 13: Plot of the electronic energy versus φ2.

68


Figure 14: Comparison of the initial structure of 6b (left) and the structure after a 360.0° rotation

around the dihedral angle φ1.

In the case of decreasing φ1, i.e. increasing φ2, the orientation of the t-butyl group resulting

at φ2= 185.0° lead to problems in the following incremental steps. The t-butyl groups are

oriented in such a fashion, that with further decrease of φ1 they are "pushed" towards the fer-

rocene moieties, resulting in massive distortion of the structure after geometry optimisation

(cf. Figure 15). At the point of φ1= –174.9° (φ2= 277.4°) the distortion lead to major difficul-

ties within the calculations, to a point where it was decided to refrain from further attempts

to continue the scan. The data acquired through this calculations are a strong indication for

Figure 15: Structure of 6 calculated at φ1= –174.9°, with the t-butyl groups eclipsing the ferrocene

moieties.

the fact that the energy barrier for the rotation around the C(1)–C(15) bond is high enough

to avoid a conformational change from 6b to 6a. Therefore, they are best described as at-

ropisomers of each other, under the assumption that the proposed structure of 6a is correct.

In order to obtain further evidence of the structure, 1H-NMR spectra for the two compounds

69


were calculated. The signals of the ferrocenyl protons of protonated 6a and 6b differ signif-

icantly from each other (cf. Figure 9). Deprotonation of 6a only showed minimal influence

on the chemical shifts of the ferrocenyl protons (for the chemical shifts of deprotonated 6a).

Molecular dynamics were not incorporated into the calculations, due to the complexity of the

molecule and solvent influences were not considered. Therefore, the results correspond to the

rigid molecule in gas phase, with a tendency toward stronger downfield shifts and can only

be used for a qualitative comparison with the actual NMR spectra. For the matter of better

understanding the Cp protons are labelled as depicted in Scheme 58.

SOt-Bu

H(3)H(2)

H(1)

Scheme 58: Labels of the Cp protons on compound 6.

The most noticeable difference in the spectra of 6a and 6b is the signal of H(3) which lies at

δ 3.99 ppm for 6a and at δ 5.48 ppm for 6b. This strong difference in chemical shift can also

be found in the calculated NMR spectra, in which the corresponding signals have a value of

δ 4.37 ppm for 6a and at δ 6.62 ppm for 6b (cf. Table 16).

Compound 6a Compound 6b

label calc.a,b,c meas.a calc.a,b,c meas.a

H(1) 4.47 4.29 4.47 4.41

H(2) 4.13 3.96 4.47 4.48

H(3) 4.37 3.99 6.62 5.48avalues given in ppm. bB3LYP/cc-pVTZ. cin gasphase.

Table 16: Comparison of calculated and measured chemical shifts.

The difference in the chemical shifts of H(3) between 6a and 6b can be explained by the

position of H(3) relative to the opposing ferrocene moiety. While in the case of 6a H(3) lies

above the Cp plane of the opposing ferrocene, in 6b it is positioned lateral to the ferrocene

adjacent to the iron centre. Therefore, a stronger influence of the ring current of the opposing

ferrocene can be assumed to lead to the relatively strong downfield shift.

70

4.4 Synthesis and structural features of BiFeS 7

4.4 Synthesis and structural features of BiFeS 7

As complexation experiments with BiFeSO 6b were unsuccessful (cf. Section 4.2), in an addi-

tional experiment it was reduced to give the dithioether 7 (BiFeS). It was assumed that the

thioether, as it provides two lone pairs at the sulfur atom instead of only one in case of the

sulfoxide, could more easily form a chelate and therefore would be more prone to undergo co-

ordination. The reduction of BiFeSO 6b to BiFeS 7 was achieved by refluxing it in dry toluene

with an excess of triethyl amine and trichlorosilane (cf. Scheme 59). Remaining starting mate-

rial was easily separated through column chromatography from the product. Recrystallisation

from DCM/n-pentane gave dark orange-red crystals suitable for X-ray diffraction (cf. Section

4.5).

FeFe

SSO

O

20 equiv NEt340 equiv SiHCl3toluene, reflux, 15h

FeFe

SS

6b 7

Scheme 59: Reduction of BiFeSO 6b to BiFeS 7.

As for BiFeSO 6b, a variety of complexation experiments were performed relying mainly on

DMS based precursors in order to take advantage of the possible chelating effect of the BiFeS

7. The attempts failed to yield an isolated complex. However, refluxing BiFeS 7 with HgBr2 in

toluene gave a small amount of a precipitate that appeared to be a new product. NMR analysis

seemed to indicate that an elimination of one of the t-butyl groups was taking place, similar

to the decomposition of di-t-butyl sulfide-mercury(II) chloride reproted by Biscarini et al. (cf.

Scheme 60).[265]

Attempts to increase the yield by further addition of HgBr2, longer reaction times or higher

temperature, as well as the addition of base in order to facilitate the elimination, were un-

successful. Attempts using other mercury precursor precursors, such as HgCl2 and Hg(CF3)2,

didn’t yield any detectable product at all, therefore no full characterisation could be per-

formed. As a final attempt BiFeS 7 was reacted with ZnEt2 in THF, but only the starting

material was isolated.

71


S

H2C

Hg

Cl

Cl Hg

Cl

ClH

S

CH2H

Scheme 60: Decomposition mechanism of [t-Bu2SHgCl2]2 as proposed by Biscarini et al.[265]

4.5 X-ray structure of BiFeSO 6b and BIFES 7

As mentioned above, X-ray structures for both compounds BiFeSO 6b and BiFeS 7 were

measured. Both compounds crystallised in an orthorhombic cell system with a P212121 space

group and showed very similar structure (cf. Figure 16). The dihedral angles φ1 and the

angles between the two Cp-rings φ2 of the two compounds, as defined in Section 4.3, are

very similar to each other with values of φ1= 125.0(3)° and φ2= 49.4° for BiFeSO 6b and

φ1= 125.9(2)° and φ2= 48.6° for BiFeS 7. As expected the main difference between the two

compounds is found in the dihedral angles around the sulfur moieties, which differ in a range

of 8 – 14° (cf. Table 17). At the same time the angles at the sulfur atoms only differ marginally

in a range of 1 – 2°.

C2C1

C16

C15

S2

C25

C11

S1

Fe2Fe1

C1 C2S1

O1

C15

C16

S2O2

C25

C11

Fe1Fe2

C17 C3C3

C17

Figure 16: Structures including labels of BiFeSO 6b and BiFeS 7.

Concerning the bond lengths only marginal differences can be observed between the com-

72

4.5 X-ray structure of BiFeSO 6b and BIFES 7

Angle BiFeSO 6b [°] BiFeS 7 [°]

φ1 125.0(3) 125.9(2)

φ2 49.4 48.6

C2–S1–C11 102.23(10) 103.89(8)

C16–S2–C25 103.67(10) 105.73(8)

O1–S1–C2 111.02(10)

O2–S2–C16 110.67(9)

O1–S1–C11 107.02(10)

O2–S2–C25 105.87(10)

C11–S1–C2–C1 –85.0(2) –92.74(17)

C25–S2–C16–C15 –81.9(2) –94.92(17)

C11–S1–C2–C3 103.49(17) 93.33(15)

C25–S2–C16–C17 107.87(19) 93.88(17)

Table 17: Selected angles from the X-ray structures of 6b and 7.

pounds. Only the CCp–S bonds (S1–C2 and S2–C16) differ significantly from each other, with

a difference of about 0.02 Å (cf. Table 18) in correspondence to the known average Carom–S(3)

and Carom–S(2) bond lengths.[266] At the same time the lengths of the Csp3–S bonds are not

effected by the reduction of the sulfoxide to the sulfide.

Bond BiFeSO 6b [Å] BiFeS 7 [Å]

C1–C15 1.472(3) 1.465(2)

S1–C2 1.785(2) 1.7623(17)

S2–C16 1.781(2) 1.7632(18)

S1–C11 1.851(2) 1.8502(18)

S2–C25 1.851(2) 1.8546(18)

S1–O1 1.4977(18)

S2–O2 1.4978(16)

Table 18: Selected bond lengths from the X-ray structures of 6b and 7.

73


4.6 Summary

Enantiomerically pure BiFeSO 6 and BiFeS 7 were successfully synthesised. The synthesis of

BiFeSO 6 yielded two materials that matched the analytic data expected for the desired prod-

uct. However, significant differences between the two compounds were found, suggesting the

formation of two atropisomers of BiFeSO (6a and 6b). Quantum chemical calculations were

performed in order to provide further support for this hypothesis. The quantum chemical cal-

culations predicted a high activation energy for conformational change from one atropisomer

to the other. In addition, calculated NMR spectra of the suggested structure of 6a and of 6b

corresponded to the measured NMRs by qualitative comparison. Complexation of the BiFeSO

6 and BiFeS 7 to several transition metals was unsuccessful, with the exeption of the reac-

tion of BiFeS 7 with mercury(II)bromide, which indicated that a complexation of the mercury

with subsequent elimination of the t-butyl group. However, the resulting product could not be

isolated and this conclusion remains speculative.

74

5 Side projects

5.1 Introduction

In addition to the research described in Chapters 2 to 4, complementary side projects were

undertaken to complement the findings of the primary work.

5.2 Acidity of [Ni(II)-(Pigiphos)L]2+

As [Ni(II)-(Pigiphos)L]2+ is a chiral Lewis acid (cf. chapter 2.1), a method to determine the

acidity of the dicationic complex would be of interest. However, due to the complexity of the

compound, a direct comparison with common Lewis acids is likely to be challenging. Still, an

estimation of its acidity could be made and would be of interest, especially for comparison

with other Pigiphos derivatives.

5.2.1 Fluoride Ion Affinity

Determination of acidity of Lewis acids has been a matter of more or less continuous interest.

For comparative studies Lewis acid interactions with α,β-unsaturated carbonyls and nitriles

have been used in combination with NMR-shifts and calorimetric studies to estimate Lewis

acidity.[267–270] Fluoride ion affinity (FIA) is a more generally applicable method for acidity

determination and is often used. Because of the fluoride ion’s small size and high basicity,

it tends to react with almost all hard Lewis acids. By definition the FIA corresponds to the

negative enthalpy of the reaction of the Lewis acid with F− in gas phase. There are several

FIA scales based on measurements, the precision of which is limited by problems stemming

from experimental factors that arise if reactions cannot be performed in the gas phase or if

lattice energies of the often solid products are not known.[271,272] Also determination methods

often give variable results leading to relatively large uncertainties of around 10 %. Therefore

computational methods based on the isodesmic reaction (1) may be used to determine the

FIA,[273–276] based on the experimental FIA value of OCF2.[271]

A + OCF−3 → AF− + OCF2 (1)

In the case of [Ni(II)-(Pigiphos)L]2+ neither approach would be feasible, as the compound

cannot be brought into the gaseous phase and at the same time is too complex to assess

computationally. So, comparative studies to known values are necessary to estimate the actual

FIA of the dicationic [Ni(II)-(Pigiphos)L]2+ system.

75

5 Side projects


In order to estimate the FIA of [Ni(II)-(Pigiphos)L]2+, the fluoride complex 8 had to be

synthesised first. The [fluoro-Ni(II)-(Pigiphos)]+ complex 8 could then be mixed with a Lewis

acid in a 1:1 ratio and the ratio of fluorinated Lewis acid and [Ni(II)-(Pigiphos)L]2+ could then

be estimated, preferably by 19F-NMR. Therefore, for the reaction of [fluoro-Ni(II)-(Pigiphos)]+

(NiF+) with a Lewis acid (A) (cf. (2)) K can be calculated from equation (3).

NiF+ + A � NiF2+ + AF− (2)

K=[Ni2+][AF−][NiF+][A]

(3)

Equation (3) can be rewritten as equation (4) by assuming that [Ni2+] = [AF−] and [NiF+] =

[A]:

K=[AF−]2

[NiF+]2(4)

Now K can be calculated solely based on the integrals of the 19F-NMR spectra and therefore

the Lewis acidity can be quantified relative to the competing Lewis acid. When K > 1 the FIA

value of the Lewis acid lies above the FIA value of [Ni(II)-(Pigiphos)L]2+ and vice versa for

K < 1.

5.2.3 Synthesis of [fluoro-Ni(II)-(Pigiphos)]+

The synthesis of the desired fluoride complex 8 was challenging. To minimise the influence

of the counter ion on the acid base reactions, the complex was synthesised from [Ni(II)-

(Pigiphos)L]2+ perchlorate by adding TBAF or TMAF as fluoride sources under different con-

ditions. Although later experiments showed that the complex was partially fluorinated, the

desired product could not be isolated in a satisfactory purity or yield. Attempts to force halo-

gen exchange starting from the chloro analogue by using fluoride based halogen scavengers

were equally unsuccessful. The desired fluoride complex 8 was synthesised by first forming

the Ni(0)-Pigiphos complex by reacting Pigiphos with [Ni(COD)2],[277] followed by the addi-

tion of fluoropyridinium salt 39 as electrophilic fluorine source (cf. Scheme 61).

76


Fe

PFe

PPh2 Ph2P

Cy [Ni(COD)2]

tol, 1h at rtFe

PFe

Ph2P PPh2

Cy

Ni

N+FBF4

-

tol, 24h at rtFe

PFe

Ph2P PPh2

Cy

Ni

F

+

BF4-39

8

Scheme 61: Synthesis of the [fluoro-Ni(II)-(Pigiphos)]+ 8 from Pigiphos and [Ni(COD)2] using fluo-

ropyridinium salt 39

The deep red solid compound showed a very broad signal around δ –323 ppm in 19F-NMR

as well as the presence of several impurities, while 31P-NMR showed the presence of other

[Ni(II)-(Pigiphos)L]2+ complexes in addition to the desired product. The formation of the Ni–

F bond was unequivocally demonstrated by a 162 MHz 19F,31P-HMBC-NMR experiment, which

show correlations between the fluorine signal and the coordinated phosphorus atoms of the

Pigiphos ligand (cf. Figure 17).

Recrystallisation of the product from DCM/n-pentane lead to polycrystalline material as well

as some single crystals suitable for X-ray crystallography. Although the crystals were of poor

quality and therefore did not allow a complete solution of the crystal structure, Ni–F connec-

tivity could still be confirmed. No clear assignment of the NMR signals could be made due to

impurities, even after recrystallisation, as well as due to the broad signals mainly in 1H-NMR,

the latter can be explained by inspection of the crystal structure of the fluoride complex 8.

As the solution of the crystal structure of the tetrafluoroborate salt 8 was not complete (vide

supra), the structure of the pentafluoro silicate salt of [fluoro-Ni(II)-(Pigiphos)]+, synthesised

by Sandra Miloševic in our group, was used to determine the geometry at nickel (cf. Figure

18). The sum of the angles around the nickel(II) centre add up to 361°. Therefore the ge-

ometry is distorted from a perfect square planar configuration. This is further confirmed by

77

5 Side projects

102060 f2

50(ppm)

40 30708090

-330

-325

-320

-315

f1 (ppm)

Figure 17: 162 MHz 19F,31P-HMBC-NMR of [fluoro-Ni(II)-(Pigiphos)]+ 8.

the angles F(1)–Ni(1)–P(2)=175.49(9)° and P(1)–Ni(1)–P(3)= 162.74(4)°, which differ sig-

nificantly from 180° for a linear arrangement. The distorted square-planar geometry should

result in paramagnetic character. As a result of this geometric distortion, the quality of the

NMR spectra suffers due to line broadening and the concentration dependence of the absolute

chemical shifts.

P1

P2Ni1

P3

F1P1

P2Ni1

P3

F1

Figure 18: X-ray structure of the [fluoro-Ni(II)-(Pigiphos)]+. left: the structure from the tetraflorobo-

rate salt 8. right: the structure from the pentafluorosilicate salt.

78


In order to exclude exchange effects as the source of the signal broadening, a series of variable

temperature 19F-NMR spectra were recorded. Temperature dependent 19F-NMR spectra were

measured in a range between 193 K and 263 K. A large temperature dependence of chemical

shift of the coordinated fluoride was observed with an up-field shift from δ –315 ppm at 263 K

to δ –293 ppm at 193 K with the signal almost vanishing at 223 K (cf. Figure 19).

−285 −290 −295 −300 −305 −310 −315 −320 ppm

223

213

203

193

233

263

253

243

T/K

Figure 19: Temperature dependent 376.5 MHz 19F-NMR of [fluoro-Ni(II)-(Pigiphos)]+ 8.

As only a single signal was affected by the temperature change, namely the signal of the flu-

oride bound to the nickel(II) centre, an exchange of that fluoride is unlikely. The most likely

explanation is the configurational change between two tetrahedrally distorted configurations

around the nickel(II) moiety. At high temperature (above 233 K) the exchange between the

two configurations is fast enough to give an average value corresponding to a quasi square

planar complex. At low temperature (below 223 K) the exchange rate between the two con-

figurations becomes significantly slower than the time scale of the NMR experiment. As a con-

sequence, the paramagnetic term is fully expressed, and since the distorted configurations are

not averaged out, the resulting shift of ∆δ 22 ppm in a temperature range of 70 K is observed.

Due to the C1 symmetry of the complex, the two distorted configurations are not equivalent

to each other, as a consequence the paramagnetic term does not vanish completely at high

temperature, hence the concentration dependent chemical shifts, as well as line broadening

caused by paramagnetism are observed at rt. Due to the problems concerning the purification

of complex 8 and the inaccuracy of the fluoride’s integral in 19F-NMR as a consequence of

paramagnetism the method was considered not to be suitable for FIA estimation.

79

5 Side projects

5.2.4 Summary

An attempt to quantify the FIA of the [Ni(II)-(Pigiphos)L]2+ resulted in the development of a

synthetic route towards a [fluoro-Ni(II)-(Pigiphos)]+ complex. The compound showed para-

magnetic properties in NMR, that can be explained through the measured crystal structure

and the dynamics of the complex were observed by temperature dependent 19F-NMR. Unfor-

tunately, the synthesised system was found not to be suitable for FIA determination due to

purification difficulties as well as the paramagnetic character of the nickel(II) complex.

5.3 Towards a chiral ferrocenyl building block

In the course of synthetic work on the PSiP- and PPP-pincer analogues one of the principal diffi-

culties encountered was the oxygen transfer from the sulfoxide to electrophiles during the sub-

stitution reactions (cf. Chapter 3.3.3). Removal or substitution of the sulfoxide prior to the con-

cerned reactions could therefore be a possibility to avoid the problems encountered. In order

to introduce planar chirality, a chiral 1,2-disubstituted ferrocene containing substituents that

can be selectively substituted with another group would be required. One compound consid-

ered to be useful for such an application is bromo-2-(tri-n-butylstannyl)ferrocene 9. As prob-

lems due to oxygen transfer only were encountered either during the coupling of the two fer-

rocenes over a central moiety, using a dichlorosilane or a dichlorophosphine, or in the substi-

tution of the p-tolylsulfoxide with a chlorophosphine, bromo-2-(diphenylphosphino)ferrocene

40 was investigated as another compound able to circumvent the problems of the coupling

step.

5.3.1 The bromo stannyl ferrocene

Bromo-2-(tri-n-butylstannyl)ferrocene 9 was synthesised from the known (RFc,SS)-(p-

tolylsulfinyl)-2-(tri-n-butylstannyl)ferrocene[75] 41 by substituting the sulfoxide using t-BuLi

and dibromotetrachloroethane (cf. Scheme 62). During the course of this work, this re-

action was also reported by Zirakzadeh et al. in their attempt to synthesis new Walphos

analogues.[253]

Due to the n-butyl groups attached to the tin moiety, access to the ortho position is restricted.

Therefore, the reaction always yielded a mixture of bromo-2-(tri-n-butylstannyl)ferrocene 9

and (tri-n-butylstannyl)ferrocene in a ratio of 1:1 up to 2:1 in favour of the desired product

as determined by 1H-NMR. As both products are highly apolar oils, their separation was

80


Fe Fe

SnBu3

S OSnBu3

Br1. t-BuLi

2. CH2BrCH2Br

9

Scheme 62: Synthesis of bromo-2-(tri-n-butylstannyl)ferrocene 9.

challenging. Two flash column chromatographies over silica using n-pentane as eluent gave a

ratio of 4:1 of the desired product 9 to the side product (Zirakzadeh et al. encountered similar

problems), a purity that was considered sufficient for preliminary experiments.

For the selective substitution step three different approaches were considered. Initial attempts

were based on selective lithiation taking advantage of the fact that n-butylstannyl substituents

are not affected by t-BuLi due to steric hindrance. In a second step the stannyl substituent

could then be lithiated using n-BuLi. Another approach considered was the substitution of

the stannyl by following the method reported by Mita et al., using fluoride as a mild tin

activator.[278–281] Although Stille coupling would not enable the synthesis of a PSiP-pincer

like ligand, as described in Chapter 3, the initial motivation for the synthesis of a chiral

building block, it was investigated for its utility in the synthesis of other chiral 1,2-substituted

ferrocenes (cf. Scheme 63).

BrFe

Sn1. t-BuLi

2. EX

Stille coupling

with RX

1. CsF2. EX

EFe

Sn

BrFe

E

BrFe

R

9

Scheme 63: Suggested ways of selective substitution at the bromo-2-(tri-n-butylstannyl)ferrocene 9.

81

5 Side projects

5.3.1.1 Selective lithiation The simplest method for selective substitution is through se-

lective lithiation of the reactive sites. As mentioned previously (vide supra), the n-butylstannyl

substituent is usually unaffected by t-BuLi due to steric hindrance, while the bromine lithium

exchange is likely. Several attempts under different conditions (reaction times at different

temperatures) were performed using chlorodiphenylphosphine as an electrophile. The results

were comparable for all conditions applied. After work-up only traces of product (up to 5 %

NMR-yield with respect to compound 9) were present in the crude product. Flash column

chromatography lowered the yield further, while the applied starting material was recovered.

It was assumed that the access to the bromo substituent was hindered by the sterically de-

manding tri-n-butylstannyl group. Attempts using n-butyllithium lead to an almost 1:1 ratio

of lithiation of the stannyl and the bromo substituent.

5.3.1.2 Fluoride based tin cleavage The activation of the stannyl group by fluoride ad-

dition was considered as a preliminary approach. Experiments were performed on (tri-n-

butylstannyl)ferrocene. A variety of fluoride sources were tested, but no activation was ob-

served and further attempts were abandoned.

5.3.1.3 Stille Coupling A few Stille coupling experiments of bromo-2-(tri-n-

butylstannyl)ferrocene 9 to aromatic halides and pseudohalides were performed with

no success. Additionally, experiments coupling bromo-(tri-n-butylstannyl)ferrocene 9 to itself

were undertaken to see if a poly-Stille coupling to a poly 1,2-ferrocenyl or the synthesis

of 1,2,1”,2”-biferrocene by a double Stille coupling would be possible. Following reaction

conditions reported by Liebeskind et al.[282] a small portion of impure material was obtained,

that showed the mass of the singly coupled product in HRMS (Dual MALDI/ESI: m/z calcd

for C32H43BrFe2Sn: 738.0262, found: 738.0251), but the structure could not be verified by

NMR. As for all the performed Stille couplings, also in this experiment the majority of the

starting material was recovered.

5.3.2 The Bromo phosphino ferrocene

As mentioned above, the primary motivation for the synthesis of a chiral building block,

was to circumvent problems encountered with the sulfoxide in the PSiP-pincer ligand syn-

thesis described in Chapter 3. A less sophisticated solution to do so was the synthesis of a

82


1-bromo-2-phosphino-ferrocene as an intermediate between the sulfoxide and the pincer sys-

tem. To obtain the desired material (p-tolylsulfinyl)-2-[diphenylphosphino(borane)]ferrocene

33 was first treated with t-butyl lithium to give lithiated phosphinoferrocene and subsequently

quenched by a brominating agent. Initial attempts using bromine as bromination agent

gave yields less than 5 % (estimated by 1H-NMR). Attempts using halon 2402 (2 equiv), 1,2-

dibromoethane (3 equiv) or 1,2-dichlorotetrabromoethane (2 equiv) gave comparable NMR

yields, slightly greater than 15 %. Due to the environmental impact of halon 2402 and

the health concern regarding the use of 1,2-dibromoethane, 1,2-dibromotetrachloroethane

seemed to be the ideal brominating agent for these purposes. The low yield is not a matter of

low conversion in the lithiation step, but seems to be due to incomplete bromination. The main

product obtained by this reaction was [diphenylphosphino(borane)]ferrocene, which could

not be seperated completely from the desired product by standard methods. Therefore, the de-

sired product was always obtained as a mixture with [diphenylphosphino(borane)]ferrocene

in varying ratios (from 1:3 to 1:1). Adjusting the reaction time, temperature or reagent

concentrations had no observable impact on the yield of the reaction, although under iden-

tical conditions the yields varied significantly from one experiment to the next (usually

between 10 and 20 %, with the exception of one experiment yielding 50 %). As all at-

tempts to separate bromo-2-[diphenylphosphino(borane)]ferrocene 33 from [diphenylphos-

phino(borane)]ferrocene were unsuccessful, the product mixture was just separated from the

starting material, as well as the t-butyl-p-tolyl sulfoxide generated during the reaction by flash

column chromatography using ether as an eluent. Then the product mixture was deprotected

by refluxing it in degassed diethylamine. Separation difficulties persisted after the deprotec-

tion, but small amounts of the desired product were obtained for characterisation by prepara-

tive HPLC.

5.3.3 Summary

In an attempt to create a enantiomerically enriched 1,2-substituted ferrocenyl build-

ing block, the syntheses of bromo-2-(tri-n-butylstannyl)ferrocene 9 and bromo-2-

[diphenylphosphino]ferrocene 40 were developed. In both cases severe purification

difficulties were encountered. The selective substitution reactions of bromo-2-(tri-n-

butylstannyl)ferrocene 9 performed met with little success. During the investigation of com-

pound 9, Zirakzadeh et al.[253] published a similar synthesis of the same compound. Their

reported substitution of the stannyl group by iodine and the resulting enantiomerically en-

riched bromoiodoferrocene might provide new possibilities for selective substitution, includ-

ing the reported Negishi coupling. The synthesis of bromo-2-[diphenylphosphino]ferrocene 40

83

5 Side projects

showed, in addition to purification issues, low yields, rendering it impracticable as an ‘inert’

replacement of (p-tolylsulfinyl)-2-[diphenylphosphino(borane)]ferocene 33.

5.4 Ferrocenyl-(trifluoromethyl) sulfide

Due to the conformational restrictions of BiFeSO 6 imposed by the t-butyl groups (cf. Chap-

ter 4), a BiFeSO with a sterically less demanding group was considered to be of interest, as

it might more easily undergo a ‘configurational’ change that would favour the complexation

of a metal. Initial attempts included i-propyl and methyl substituents, in order to assess the

size at which the energy barrier allows for a ‘configurational’ change. But the coupling reac-

tions to the biferrocenes were unsuccessful. This is most probably due to the acidity of the

hydrogen α to the sulfoxide, leading to problems with lithiation.[80] As the Togni group has

a long history of research on trifluoromethylation agents and trifluoromethylation,[283–289] a

ferrocenyl-(triflouoromethyl) sulfoxide appeared as logical path to achieve the requirements.

5.4.1 Synthetic approach

In order to achieve enantiomerically pure bis-[2-(trifluoromethylsulfinyl)ferrocene],

ferrocenyl-(trifluoromethyl) sulfide had to be synthesised in a first step. The sulfide

would then be enantioselectively oxidised to give enantiomerically enriched ferrocenyl-

(trifluoromethyl) sulfoxide, suitable for the coupling reaction to the biferrocene.

Although ferrocenyl-(trifluoromethyl) sulfide has been previously reported by Rhode et

al.,[290] due to the tedious preparation and inadequate characterisation this route has not

been considered. Initial attempts included the palladium-catalysed formation of ferrocenyl-

(trifluoromethyl) sulfide from bromoferrocene and AgSCF3 analogous to the Ar–SCF3 synthe-

sis reported by Buchwald and co-workers.[291] As these attempts turned out to be unsuccessful,

the trifluoromethylation of ferrocene thiol using the alcohol and acid Togni reagents were in-

vestigated (cf. Scheme 64).

The major product obtained from the reaction of ferrocene thiol with the Togni reagents was

bisferrocenyl disulfide, due to the oxidation of the thiol by the iodine(III). Nonetheless, the

reaction of sodium ferrocenesulfide with the acid Togni reagent showed the formation of small

amounts of what seemed to be the desired product, with the best results being achieved by

performing the reaction in DCM at –78 ◦C up to rt with no additives, yielding up to 10 % of the

desired product (identified by HRMS and NMR). Still the main product of the reaction was the

bisferrocenyl disulfide with 50 % and the absolute yields achieved did not exceed 60 mg as the

84

5.4 Ferrocenyl-(trifluoromethyl) sulfide

Fe

S CF3

Fe

SHTogni reagent

IF3C O IF3C O

O

Togni reagents

alcohol reagent acid reagent

Scheme 64: Synthesis of ferrocenyl-(trifluoromethyl) sulfide using Togni reagents.

ratio of products changed in disfavour of the desired product, when the reaction was scaled up.

Selective oxidation experiments did not lead to any clear results, as the amount of ferrocenyl-

(trifluoromethyl) sulfide obtained was to small to perform extensive studies. Therefore the

project was ceased at this point.

5.4.2 Summary

With the initial intention to obtain an enantiomerically enriched ferrocenyl-

(trifluoromethyl) sulfoxide, the synthesis of ferrocenyl-(trifluoromethyl) sulfide was

performed by applying the Togni acid reagent to sodium ferrocenylsulfide. Although oxi-

dation of the sulfide to the disulfide was the principal product observed, a small amount

of ferrocenyl-(triflouromethyl) sulfide was synthesised as indicated by NMR and HRMS

experiments.

85

5 Side projects

86

6 Conclusion and Outlook

6.1 PSiP-Pigiphos

So far, the synthesis of a PSiP-Pigiphos analogue 1 has been unsuccessful. The main problem

arises from the need for either a nucleophilic silicon moiety or a nucleophilic ‘benzylic’ carbon

atom on the ferrocene. The most promising approach to the desired ligand included a Corey-

Seebach-Umpolung at the ‘benzylic’ position after the introduction of planar chirality through

directed ortho lithiation, using a chiral acetal. Although double substitution of silicon was

unsuccessful, a PSi ligand 2 was synthesised with the method developed, which undergoes

Si–H activation with Pt(0) as shown in NMR.

Further investigation of the new PSi ligand 2 and its complexes would be of interest as it

represents, to the best of our knowledge, the first enantiomerically pure PSi ligand.

6.2 PSiP-pincer like ligand

The synthesis of a chiral PSiP pincer analogue 3, which would form five membered metal-

lacycles upon Si–H activation, was unsuccessful, as was the enantioselective synthesis of its

PPP analogue 4. Problems were mainly encountered due to interaction of sulfoxide with the

stronger electrophiles in the coupling step. Nonetheless, the bissulfoxyphosphine interme-

diate 9 obtained during the attempted synthesis of 4 formed complexes with palladium(II),

platinum(II) and rhodium(I). While the structure of the palladium(II) and platinum(II) com-

plexes were determined, the formation of a rhodium complex could only be indicated by

mass spectrometry, 31P-NMR and through asymmetric catalysis, more precisely in the Miyaura-

Hayashi reaction, in which moderate enantiomeric excess was achieved (16 %ee) with low

yields (14 %).

The palladium(II) complex 42 showed activity in allylic substitution, giving good yields (95 %)

and moderately high enantiomeric excess (78 %ee). The use of the palladium(II) 42 and plat-

inum(II) 43 complexes in a wider catalytic scope should be investigated as well as the optimi-

sation of the allylic substitution reaction. Further the investigation of the role of the unbound

sulfoxide moiety on the enantiomeric selectivity could be of interest.

Although preliminary complexation experiments with early transition metals were not yet

successful, further studies in this direction might be of interest, as the oxygen atoms at the

sulfoxide moieties might act as donors to harder metal centres.

87


6.3 Biferrocenylsulfoxide and Biferrocenylsulfide

Bis(ferrocenylsulfoxide) (BiFeSO) 6 was synthesised successfully, giving two products with

same connectivity as indicated by NMR spectra. The two products 6a and 6b appear to be

atropisomers. In order to substantiate this conclusion, quantum chemical calculations were

performed to estimate the energy barrier to a conformational change from the fully charac-

terised BiFeSO 6b to the suggested structure 6a. The outcome of the calculations suggest that

a conformational change would not take place at rt. The calculated 1H-NMR spectra of 6b and

those of 6a showed qualitative correspondence to the measured 1H-NMR spectra, with regards

to the Cp protons. 6a showed peaks of acidic protons after work-up with aqueous solutions.

Although the counterion of the resulting compound could not be discerned, the acidic nature

of the protons was proven by deprotonation with NaOH, as well as by a deuterium–protium

exchange. Further investigation is needed in order to confirm the actual structure of 6a.

In a next step, 6b was reduced to give bis(ferrocenylsulfide) (BiFeS) 7. While BiFeSO 6b did

not undergo complexation with a large variety of transition metal precursors, BiFeS 7 seemed

to result in partial elimination of iso-butene, when treated with HgBr2. This reaction may be

further investigated. Also, a forced elimination of iso-butene iso-butene could be of interest in

order to produce bis(ferrocenylthiol), which might more readily undergo complexation.

6.4 Side Projects

6.4.1 Acidity of [Ni(II)-PigiphosL]2+

The synthesis of fluoro-Pigiphos-nickel(II) tetrafluoroborate 44 was developed. 19F-NMR-

spectra revealed the paramagnetic nature of the complex, making it unsuitable for the in-

tended FIA estimation of the Ni(II)-Pigiphos system. As the approach failed, another experi-

mental set-up should be developed in order to enable an FIA estimation.

6.4.2 Ferrocenyl building block

A synthetic route towards bromostannylferrocene 9 and bromophosphinoferrocene 40 were

developed. While selective substitution of either the stannyl group or the bromine in 9 was

unsuccessful, the approach to an ‘inert’ building block in the form of 40 failed due to low

yields and purification problems.

During the course of this work, Zirakzadeh et al.[253] reported a similar synthesis of com-

pound 9. They exchanged the stannyl group in a further step with iodine to use the resulting

88

6.5 General outlook

enantiomerically pure bromoiodoferrocene in Negishi coupling. The bromoiodoferrocene they

reported should be further exploited for its use in other palladium catalysed couplings, as the

selectivity of palladium towards iodine is enough to obtain highly enantiomerically enriched

products.

6.4.3 Ferrocenyl-(trifluoromethyl) sulfide

(Trifluoromethyl)ferrocenylsulfide 10 was synthesised from sodium ferrocenylsulfide 45, us-

ing the Togni acid reagent. Yields were low, as mainly the oxidation to ferrocenyldisulfide pre-

dominated. Other approaches using different trifluoromethylating agents or trifluoromethylth-

iolating agents should be investigated.

6.5 General outlook

In order to expand the asymmetric tridentate ligand concept, alternative designs, such as the

PSiP pincer-like ligand 31 reported by Turculet and co-workers,[132] seem tenable. If the pe-

ripheral phosphines are substituted with a chiral substituent (e.g. (–)-menthyl) and an achiral

alkyl or aryl group, the resulting diastereomeric mixture should be separable. As a result an

enantiomerically enriched ligand could be obtained with stereoinformation at the phosphine

donors. An analogous process could lead to a PPP derivative, therefore enabling comparative

studies between the PSiP and PPP systems (cf. Scheme 65).

SiP P

menth

R

Rmenth

Me

HP

P Pmenth

R

Rmenth

R'Si

P PPh2

Me

HPh2

31

Scheme 65: Proposed chiral tridentate ligands, derived from Turculet’s PSiP ligand 31.

89


90

7 Experimental

7.1 General Remarks

7.1.1 Techniques

All reactions and manipulations involving air- or moisture-sensitive compounds were car-

ried out under an inert atmosphere of argon using standard Schlenk techniques[292] or in a

glove box (MBraun MB 150B-G and Lab Master 130) under an atmosphere of dry nitrogen.

Glassware were preheated to 140 ◦C in a drying oven or dried under HV with a heat gun

and then purged with argon. Dry solvents were freshly distilled under an argon atmosphere

over sodium/benzophenone (toluene, THF, diethyl ether), sodium/benzophenone/diglyme (n-

pentane), sodium/benzophenone/tetraglyme (n-hexane), sodium/diethyl phthalate (EtOH)

or calcium hydride (MeOH, CH2Cl2, CH3CN, toluene). Solvents used for synthetic and recrys-

tallisation purposes were of "puriss p.a." quality (Sigma-Aldrich, Riedel-de-Haen, J.T. Baker

or Merck) and were, if necessary, degassed by saturating with argon or by 3 freeze-pump-

thaw cycles. For flash chromatography and TLC, technical grade solvents were generally used.

Deuterated solvents were purchased from Cambridge Isotope Laboratories or Armar Chemi-

cals (CDCl3). For use with sensitive compounds they were purified by bulb-to-bulb distillation

from Na (C6D6) or CaH2 (CD2Cl2), degassed by 3 freeze-pump-thaw cycles and stored under

argon in a Young Schlenk tube.

7.1.2 Chemicals

Commercially available chemicals were purchased from ABCR, Acros AG, Sigma-Aldrich, TCI

or Pressure Chemical Co. and metal precursors from Johnson Matthey (Na2PdCl4, IrCl3 ·3 H2O)

and used without further purification. (S)-(–)-1,2,4-butanetriol was either purchased from

ABCR or synthesised from malic acid.[83] (1R,2S,5R)-(–)-menthyl-(S)-p-toluenesulfinate was

purchased from TCI and recrystallised or synthesised from (–)-Menthol and sodium p-

toluenesulfinate.[293,294] (R)-Ugi’s amine was kindly provided by Solvias AG (Basel) as a tar-

trate salt and was obtained as enantiomerically pure free amine following a modified version

of the procedure described by Ugi.[49] If necessary the concentration of butyllithium reagents

was determined by titration against diphenyl ditelluride.[295]

91

7 Experimental

7.1.3 Analytical Techniques and Instruments

Thin layer chromatography (TLC) was performed on Merck Silica gel 60 (F254) visualized

by fluorescence quenching at 254 nm. In addition, permanganate (1 g KMnO4, 2 g NaCO3,

100 mL EtOH), vanillin (12 g vanillin, 2 mL H2SO4 conc., 200 mL EtOH) or iodine were used

as developing agents.

Flash column chromatography (FC) was performed on Fluka Silica Gel 60 (230-400 mesh)

using the given solvent ratios and a forced flow of eluent at 0.1 – 0.2 bar nitrogen overpres-

sure.

NMR spectra were recorded on Bruker 700 Avance, 500 DPX Avance, 400 DPX Avance, 300

DPX Avance, 300 Avance III HD Nanobay, 250 DPX Avance or 200 DPX Avance spectrometers

operating at the given spectrometer frequency. The samples were measured as solutions in the

given solvent at room temperature (if not indicated differently) and in non-spinning mode.

The chemical shifts (δ) are expressed in part per millions (ppm) relative to TMS as an exter-

nal standard for 1H- and 13C-NMR spectra analogously to IUPAC[296] and are calibrated against

the residual solvent peak. For CD2Cl2 as solvent δ = 5.32 ppm and δ = 53.8 ppm were used

for the calibration of 1H- and 13C-NMR spectra respectively. The multiplicity, if the signals are

split, are described using the abbreviations: s, d, t, q and m for singlet, doublet, triplet, quartet

and multiplet respectively or by using combinations of the aforementioned abbreviations as

dd = doublet of doublet. The absolute values of the coupling constants J are given in Hertz

(Hz).

High-resolution mass spectra (HiRes-MS) were measured by the MS-Service of the "Labora-

torium für organische Chemie der ETHZ". The signals are given as mass per charge number

(m/z).

Elemental Analysis (EA) were carried out by the microelemental analysis service of the "Lab-

oratorium für organische Chemie der ETHZ" on a LECO CHN-900 analyzer. The content of the

specified element is expressed in mass percent (%).

High Pressure Liquid Chromatography (HPLC) was run on a Hewlett-Packard 1050 Series

or an Agilent 1100 Series respectively with detection at three different wave lengths (210,

230, 254 nm) using the specified column (Diacel Chiralcel OJ, OD-H or OB-H), flow rate of

the solvents (mL/min), ratio of n-hexane/i-PrOH and sample injection volume (µL; sample

concentration approximately 1 mg/mL). Retention times tR are given in minutes (min).

Crystallography: Intensity data of single crystals glued to a glass capillary were collected at

the given temperature (usually 100 K) on a Bruker SMART APEX platform with CCD detector

and graphite monochromated Mo Kα radiation (λ = 0.71073 Å). The program SMART served

for data collection; integration was performed with the software SAINT.[297] The structures

92

7.2 Syntheses

were solved by direct or Patterson methods, using the program SHELXS 97.[298] The refine-

ment and all further calculations were carried out using SHELXL 97.[299] All non-hydrogen

atoms were refined anisotropically using weighted full-matrix least squares on F2. The hydro-

gen atoms were included in calculated positions and treated as riding atoms using SHELXL

default parameters. An absorption correction was applied (SADABS)[300] and weights were

optimized in the final refinement cycles. The absolute configuration of chiral compounds was

determined on the basis of the Flack parameter.[301,302] The standard uncertainties (s.u.) are

rounded according to the "Notes for Authors" of Acta Crystallographica.[303]

7.2 Syntheses

7.2.1 Ligands and Complexes

Fe

HOO

OH(2S,4S)-4-(Hydroxymethyl)-2-ferrocenyl-1,3-dioxane (18)[84]

C15H18FeO3, 302.15 g/mol

Ferrocenylcarbaldehyde (4.25 g, 19.9 mmol, 1 equiv) was dissolved

in 30 ml of trimethylorthoformate (274 mmol, 14 equiv) in a 100 ml

round bottom flask. A catalytic amount of p-toluenesulfonic acid

monohydrate (190 mg, 1 mmol, 5% mol equiv) was added turning

the solution from dark red to yellowish black. The reaction vessel was fitted with a drying

tube loaded with CaCl2 and the solution was stirred over night at 80 ◦C. Anhydrous K2CO3

was added and the solution was allowed to cool to rt, while stirring was maintained. The

resulting suspension was diluted with diethyl ether and filtered through celite. The filter cake

was washed with diethyl ether until the filtrate was colourless. The filtrate was concentrated

in vacuo and dried under high vacuum over night. The crude product (5.16 g) was dissolved

in 10 ml of chloroform and 15 g of 4 Å activated molecular sieve were added. (S)-(–)-1,2,4-

Butanetriol (2.11 g, 19.9 mmol, 1 equiv) was dried by azeotropic distillation using toluene

(three times) and then dissolved in 30 ml of chloroform. Camphorsulfonic acid (230 mg,

0.99 mmol, 5% mol equiv) was added to the triol solution, which was subsequently mixed

with the crude acetal solution. The reaction vessel was fitted with a drying tube loaded with

CaCl2 and the mixture stirred over night at rt. K2CO3 was added and the resulting suspension

was filtered through celite and the filter cake washed with dichloromethane. The filtrate was

then concentrated in vacuo to yield the crude product, which was purified by flash column

chromatography (1:1 cyclohexane/ethyl acetate) and recrystallised from boiling toluene to

yield the desired product as yellow crystals.

Yield: 2.89 g, 48 %. 1H-NMR (300 MHz, CDCl3): δ 5.40 (s, 1H, CHacetal), 4.32 (m, 2H,

93

7 Experimental

CHCp), 4.23 (m, 1H, OCH(CH2)2), 4.16 (s, 5H, CHCp′), 4.14 (m, 2H, CHCp), 3.93 (m, 2H,

OCH2CH2), 3.64 (s, 2H, CH2OH), 2.07 (m, 1H, OH), 1.83 (m, 1H, OCH2CHHaxCH), 1.39 (m,

1H, OCH2CHHeqCH). CAS-number: 149095-40-9

Fe

HOO

O(2S,4S)-4-(Methoxymethyl)-2-ferrocenyl-1,3-dioxane (17)[84]

C16H20FeO3, 316.17 g/mol

The dioxane 18 (3.90 g, 12.9 mmol, 1 equiv) was dissolved in

30 ml of THF and added dropwise to a suspension of prewashed

NaH (463 mg, 19.3 mmol, 1.5 equiv) in 5 ml of THF at 0 ◦C. Neat

iodomethane (1.3 ml, 2.95 g, 20.8 mmol, 1.6 equiv) was added and

the resulting reaction mixture allowed to warm to rt and stirred for 2 h. In order to destroy

excess NaH and iodomethane the reaction mixture was cooled to 0 ◦C and methanol was

added slowly. After quenching with water all solvents were evaporated in vacuo and the

residue dissolved in dietyl ether (40 ml), washed twice with water (20 ml), once with brine

(20 ml) and dried over MgSO4. After filtration through silica (diethyl ether) and evaporation

of the solvent in vacuo the product was obtained in quantitative yield.

Yield: 3.35 g, 82 %. 1H-NMR (300 MHz, CDCl3): δ 5.37 (s, 1H, CHacetal), 4.32 (m, 2H, CHCp),

4.23 (m, 1H, OCH(CH2)2), 4.16 (s, 5H, CHCp′), 4.12 (m, 2H, CHCp), 3.91 (m, 2H, OCH2CH2),

3.48 (s, 2H, CH2OMe), 3.42 (s, 3H, OCH3), 1.78 (m, 1H, OCH2CHHaxCH), 1.48 (m, 1H,

OCH2CHHeqCH). CAS-number: 149095-41-0

Fe

HOO

O

PPh2

(2S,4S,SFc)-4-(Methoxymethyl)-2-[α-

(diphenylphosphino)ferrocenyl]-1,3-dioxane (24)[84]

C28H29FeO3P, 500.35 g/mol

The acetal 17 (0.970 g, 3.07 mmol, 1 equiv) was dissolved in dry

diethyl ether and cooled to –78 ◦C. t-BuLi (1.78 ml, 1.9 M in

pentane, 3.37 mmol, 1.1 equiv) was added dropwise resulting in a

dark orange percipitate. After stirring at –78 ◦C for 15 min the mixture was allowed to warm

to rt and stirred for another 2 h. After cooling the mixture to –25 ◦C, using a o-xylene/dry

ice cooling bath, chlorodiphenylphosphine (0.67 ml, 0.83 g, 3.68 mmol, 1.2 equiv) was added

and the mixture stirred for another 30 min before warming it to rt and stirring it over night.

The reaction mixture was quenched with 2 M aqueous NaOH solution to get rid of remaining

chlorodiphenylphosphine and subsequently extracted with diethyl ether. Flash column

chromatography (9:1 cyclohexane/diethyl ether) on silica gel yielded the product as a brown

solid.

Yield: 1.26 g, 82 %. [α]D= –187° (c=0.95, CHCl3). 1H-NMR (300 MHz, CDCl3): δ

94

7.2 Syntheses

7.60 – 7.15 (m, 10H, CHarom), 5.66 (dd, JPH=2.12 Hz, 1H, CHacetal), 4.68 (m, 1H, CHCp),

4.21 (m, 2H, CHCp and OCH(CH2)2), 4.06 (s, 5H, CHCp′), 3.91 (m, 1H, CHCp), 3.80-3.67 (m,

2H, CH2CH2OCH), 3.07 (s, 3H, CH3), 2.93 (d, JHH= 5.17 Hz, 2H, CHCH2OMe), 1.73 (m,1H,

OCH2CHHaxCH), 1.46 (m,1H, OCH2CHHeqCH). 31P{1H}-NMR (121.5 MHz, CDCl3): δ –21.1

(s, 1P, FcPPh2).

Fe

SS2-Ferrocenyl-1,3-dithiane (29)[162]

C14H16FeS2, 304.25 g/mol

A 50 ml 2-neck round bottom flask was charged with Formylferrocene

(300 mg, 1.40 mmol, 1 equiv), 0.15 ml of 1,3-propanedithiol (0.16 g,

1.5 mmol, 1.05 equiv) and 10 ml of benzene and equipped with a gas inlet

tube. After cooling the solution to 0 ◦C in situ generated HCl gas (by addition

of sulfuric acid to sodium chloride) was bubbled through for 4 h. The reaction mixture was

dilluted with an additional amount of 10 ml of benzene, washed with 1 M NaOH(aq.) and

brine and dried over MgSO4 before concentration in vacuo. Recrystallisation from benzene

yielded the pure product as orange crystals.

Yield: 305 mg, 72 %. 1H-NMR (300 MHz, CDCl3): δ 4.87 (b, 1H, CHthioacetal), 4.23 (m, 2H,

CHCp), 4.15 (s, 5H, CHCp′), 4.05 (m, 2H, CHCp), 2.90 (m, 2H, SCHH), 2.74 (m, 2H, SCHH),

2.02 (m, 1H, CHH(CH2S)2), 1.77 (m, 1H, CHH(CH2S)2).

Fe

SiSS

Cl

2-Ferrocenyl-2-[(chlorodimethyl)silyl]-1,3-dithiane (28)[162]

C16H21ClFeS2Si, 396.85 g/mol

A 20ml schlenk tube was charged with the thioacetal 29 (755 mg,

2.55 mmol, 1 equiv) and 5 ml of THF cooled to –30 ◦C. n-BuLi (1.6 ml,

1.6 M in hexane, 2.6 mmol, 1 equiv) was added resulting in a colour

change of the dark yellow suspension to turn dark red-orange. After

stirring for 18 h dichlorodimethylsilane (0.16 ml, 0.17 g, 1.3 mmol, 0.5 equiv) was added

dropwise resulting in a darkening of the red solution. The reaction mixture was stirred for

another hour at –25 ◦C and then cooled to –78 to isolate the precipitate by filtration. After

resublimation the product was obtained together with a small amount of starting material as

a yellow solid.

Yield: 100 mg, <10 %. 1H-NMR (500 MHz, CDCl3): δ 4.40 (s, 5H, CHCp′), 4.29 (t,

JHH =1.8 Hz, 2H, CHCpCCp,quat), 4.18 (t, JHH =1.83 Hz, 2H, CHCpCHCp), 3.52 (ddd, JHH = 14.5,

95

7 Experimental

12.0, 2.7 Hz, 2H, SCHeqH), 2.77 (ddd, JHH = 14.5, 9.8, 3.5 Hz, 2H, SCHaxH), 2.26 (m, 1H,

CH2CHaxHCH2), 2.03 (m, 1H, CH2CHeqHCH2), 0.37 (s, 6H, SiCH3). 13C{1H}-NMR (126 MHz,

CDCl3): δ 90.9 (s, 1C, CCp,quat), 70.1 (s, 5C, CHCp′), 67.4 (s, 2C, CHCpCCp,quat), 67.3 (s, 2C,

CHCpCHCp), 38.4 (s, 1C, CCpC(S2)Si), 27.4 (s, 2C, SCH2CH2), 25.7 (s, 1C, CH2CH2CH2), 1.95

(s, 6C, SiCH3). 29Si-INEPT-NMR (59.6 MHz, CDCl3): δ 23.9 (s, 1Si).

Fe

HSS

PPh2

(SFc)-2-[α-(Diphenylphosphino)ferrocenyl]-1,3-dithiane (25)[162]

C26H25FePS2, 488.42 g/mol

A 100 ml 2-neck round bottom flask was equipped with a gas inlet tube

and charged with the phosphinoacetal 24 (1.26 g, 2.52 mmol, 1 equiv),

0.27 ml of 1,3-propanedithiol (0.29 g, 2.7 mmol, 1.05 equiv) and 20 ml of

benzene. The solution was cooled to 0 ◦C and in situ generated (by addition

of Sulfuric acid to sodium chloride) HCl gas was bubbled through the solution resulting in

the formation of a slight percipitate. Stirring and addition of HCl was continued for another

4 h, before diluting the reaction mixture with an additional 20 ml of benzene. After washing

the solution with 1 M NaOH(aq.) and brine the organic layer was separated and dried

over magnesium sulfate and concentrated in vacuo. After recrystallisation from benzene the

product was obtained as brown crystals.

Yield: 500 mg, 41 %. 1H-NMR (300 MHz, CDCl3): δ 7.61 (m, 2H, CHortho), 7.40 (m,

2H, CHortho), 7.38 (m, 1H, CHpara), 7.20 (m, 4H, CHmeta), 7.16 (m, 1H, CHpara), 5.26 (d,

JPH= 4.5 Hz, 1H, SCHS), 4.67 (m, 1H, PCCp,quatCHCp), 4.38 (m, 1H, CHCpCHCpCHCp), 4.05

(s, 5H, CHC p′), 3.98 (m, 1H, (S2CH)CCp,quatCHCp), 3.05 (ddd, JHH= 11.9, 9.9, 2.41 Hz, 1H,

), 2.92 (m, 2H, ), 2.58 (dm, JHH= 13.9 Hz, 1H, ), 2.06 (dm, J

HH= 13.9 Hz, 1H, ), 1.78

(qm, JHH=12.9 Hz, 1H, ). 31P{′1H}-NMR (121.5 MHz, CDCl3): δ –24.2 (s, 1P). HRMS

(Dual MALDI/ESI): m/z calcd for C26H25FePS2: 488.0479, found: 488.0479 [M]+. Mp:

167.5 – 169 ◦C.

Fe

SiSS

PPh2 Cl

(SFc)-2-[α-(Diphenylphosphino)ferrocenyl]-2-

[(chlorodimethyl)silyl]-1,3-dithiane (30)[162]

C28H30ClFePS2Si, 581.02 g/mol

The thioacetal 25 (100 mg, 0.205 mmol, 1 equiv) was dissolved in 2 ml of

dry THF in a 20 ml schlenk tube and cooled to –78 ◦C. n-BuLi (0.13 ml,

1.6 M in hexane, 0.21 mmol, 1 equiv) was added to the reaction mixture

96

7.2 Syntheses

and stirring continued for another 10 min before allowing the reaction mixture to warm to

rt resulting in a colour change from yellowish brown to deep red. Stirring was continued

at rt for another 20 min before cooling to –78 ◦C and adding dichlorodimethylsilane (25µl,

26 mg, 0.21 mmol, 1 equiv) is added to the reaction mixture. After 5 min of stirring the

reaction mixture started to lose its deep red colour turning into a yellowish black solution.

The solution was allowed to warm to rt and stirred for another 15 min before the addition of

3 ml of water. After extraction with chloroform the combined organic layers where washed

with water and brine, dried over MgSO4 and concentrated in vacuo. The crude product was

filtered through a column of silica gel (1:1, ether/pentane) collecting the coloured fractions.

After a flash column chromatography over silica gel (1:4, ether/pentane) the product was

obtained as a yellow solid from the second fraction with a slight impurity of starting material.

Yield: 20 mg, <16 %. 1H-NMR (300 MHz, CD2Cl2): δ 7.66 (m, 2H, CHPh), 7.37 (m, 4H,

CHPh), 7.32 (m, 2H, CHPh), 7.20 (m, 4H, CHPh), 4.69 (m, 1H, CHCp), 4.47 (m, 1H, CHCp),

4.27 (m, 1H, CHCp), 3.97 (s, 5H, CHC p′), 3.00 (m, 1H, CHH), 2.72 (m, 1H, CHH), 2.27

(m, 2H, CHH), 1.90 (m, 2H, CHH), 0.48 (s, 3H, SiCH3) 0.38 (s, 3H, SiCH3). 31P{1H}-NMR

(101.3 MHz, CDCl3): δ –22.4 (s, 1P). 29Si{1H}-NMR (59.6 MHz, CDCl3): δ 9.9 (s, 1Si).

Fe

SiSS

PPh2 H

(SFc)-2-[α-(Diphenylphosphino)ferrocenyl]-2-[(dimethyl)silyl]-1,3-

dithiane (2)[162]

C28H31FePS2Si, 546.58 g/mol

A 50 ml schlenk tube was charged with thioacetal 25 (250 mg,

0.513 mmol, 1 equiv) and 5 ml of THF and cooled to –78 ◦C before

addition of n-BuLi (0.36 ml, 1.6 M in hexane, 0.58 mmol, 1.1 equiv).

After 15 min of stirring the reaction mixture was allowed to warm to rt and stirred at rt

for 30 min resulting in a deep red coloured reaction mixture, which was then cooled back

to –78 ◦C for the addition of chlorodimethylsilane (70µl, 60 mg, 0.63 mmol, 1.2 equiv).

After stirring for 45 min the mixture was allowed to warm to rt and concentrated in vacuo.

Flash column chromatography over silica gel (15 g) using 10:1 pentane/diethyl ether and

evaporation of the solvents yielded the product as an orange foam.

Yield: 230 mg, 82 %. 1H-NMR (300 MHz, CD2Cl2): δ 7.60 (m, 2H, CHortho), 7.41 (m,

1H, CHpara), 7.37 (m, 2H, CHortho), 7.19 (m, 4H, CHmeta), 7.14 (m, 1H, CHpara), 4.60

(m, 1H, PCCp,quatCHCp), 4.56 (m, 1H, SiH), 4.39 (m, 1H, CHCpCHCpCHCp), 4.09 (m, 1H,

(S2Si)CCCp,quatCHCp), 3.98 (s, 5H, CHC p′), 2.96 (m, 2H, SCHeqH), 2.79 (m, 1H, SCHaxH),

2.65 (m, 1H, SCHaxH), 2.02 (m, 1H, CH2CHeqHCH2), 1.95 (m, 1H, CH2CHaxHCH2), 0.26

(d, JHH= 3.7 Hz, 3H, SiCH3) 0.14 (d, JHH= 3.7 Hz, 3H, SiCH3). 13C{1H}-NMR (75.5 MHz,

97

7 Experimental

CD2Cl2): δ 142.2 (s, 2C, Cphenyl,quat) 135.8 (s, 2C, CHortho), 132.8 (s, 1C, CHpara), 129.0

(s, 1C, CHpara), 128.1 (s, 2C, CHortho), 127.7 (s, 4C, CHmeta), 96.6 (s, 1C, CCp,quat), 73.8

(s, 1C,(S2Si)CCCp,quatCHCp), 71.6 (s, 1C, PCCp,quatCHCp), 70.7 (s, 5C, CHCp′), 68.9 (s, 1C,

CHCpCHCpCHCp), 38.6 (s, 1C, CCpC(S2)Si), 28.2 (s, 1C, SCH2CH2), 28.0 (s, 1C, SCH2CH2),

25.4 (s, 1C, CH2CH2CH2), –3.9 (s, 1C, SiCH3), –3.6 (s, 1C, SiCH3). 31P{1H}-NMR (121.5 MHz,

CDCl3): δ –22.3 (s, 1P). 29Si-INEPT-NMR (99.4 MHz, CDCl3): δ –13.9 (s, 1Si). HRMS (Dual

MALDI/ESI): m/z calcd for C28H31FePS2Si: 546.0718, found: 546.0715 [M]+. Mp: 108 ◦C,

203 ◦C (decomp).

Fe

SiS S

P PtPh2 PPh3

H

[κ2-((SFc)-2-[α-(Diphenylphosphino)ferrocenyl]-

2-[(dimethyl)silylo]-1,3-dithiane)(hydrido)-

(triphenylphosphino)platinum(II)] (46)[162]

C46H46FeP2PtS2Si, 1003.96 g/mol

A Young NMR tube was charged with phosphino-silane 2 (22.1 mg,

40.6µmol, 1 equiv) and tetrakis-(triphenylphosphine)platinum(0)

(50.5 mg, 40.6µmol, 1 equiv) and thoroughly purged with argon. 6.0 ml of d6-benzene were

added and the reactants were suspended therein using the sonic bath. After 6 h at rt, while

the sample has been agitated every 30 min, a white precipitate has formed and NMR showed

the formation of a hydride in the yellow-red solution.

Yield: not isolated. 1H-NMR (400 MHz, C6D6): δ 7.63 (m, 2H, CHphenyl on 2) 7.55 (m, 6H,

CHphenyl on PPh3), 7.22 (m, 2H, CHphenyl on 2), 6.92 (m, 4H, CHphenyl on 2), 6.87 (m, 9H,

CHphenyl on PPh3), 6.76 (td, JHH= 7.7, 1.9 Hz, 2H, CHphenyl on 2), 4.88 (m, 1H, CHCp), 4.22

(m, 1H, CHCp), 4.21 (s, 5H, CHC p′), 3.68 (m, 1H, CHCp), 3.08 (ddd, JHH=13.4, 11.9, 3.9 Hz,

1H, CHH), 2.37 (m, 2H, CHH and CHH), 1.77 (m, 1H, CHH), 1.68 (m, 1H, CHH), 1.52

(m, 1H, CHH), 1.48 (s with Pt satellites, JPtH=40 Hz, 3H, SiCH3), 1.43 (s with Pt satellites,

JPtH= 40 Hz, 3H, SiCH3), –1.07 (dd with Pt satellites, JPH= 155, 25 Hz, JPtH= 1065 Hz, 1H,

PtH). 13C{1H}-NMR (75.5 MHz, C6D6): δ (phenyl carbon atoms were not assigned) 105.6

(s, 1C, CCp,quat), 74.0 (s, 1C, CHCp), 71.4 (s, 1C, CHCp), 70.9 (s, 5C, CHCp′), 70.7 (s, 1C,

CHCp), 67.3 (s, 1C, CCp), 36.4 (s, 1C, Cquat(S)2), 28.0 (s, 1C, CH2), 25.1 (s, 1C, CH2), 23.9 (s,

1C, CH2), 11.1 (s, 1C, SiCH3) 6.9 (s, 1C, SiCH3) INCOMPLETE. 31P{1H}-NMR (121.5 MHz,

CDCl3): δ 30.4 (d with Pt satellites, JPP= 15.7 Hz, JPtP=1560 Hz, 1P, PPh3), 14.1 (d with

Pt satellites, JPP= 15.7 Hz, JPtP=2487 Hz, 1P, PFcPh2). 29Si-INEPT-NMR (99.4 MHz, CDCl3):

δ 15.5 (m with Pt satellites, JPtSi= 1114 Hz, 1Si). 195Pt-INEPT-NMR (53.8 MHz, CDCl3): δ

–5204.

98

7.2 Syntheses

Fe

SO(S)-Ferrocenyl p-tolyl sulfoxide (16)[69,84]

C17H16FeOS, 324.22 g/mol

A dry 500 ml two neck round bottom flask was charged with

ferrocene (31.3 g, 168 mmol, 2 equiv) and t-BuOK (477 mg,

4.25 mmol, 0.1 equiv) under argon. 330 ml of THF were added

and the resulting solution cooled to –78 ◦C. t-BuLi (42 ml, 1.9 M in pentane, 79.8 mmol,

0.95 equiv) was added dropwise over a time period of 30 min. Stirring was continued at

–78 ◦Cfor another 30 min before allowing the reaction mixture to warm to rt and further

stirring for another 30 min. Using a o-xylene/dry ice cooling bath, the suspension in the

reaction vessel was cooled to approximately -25 ◦C and added to a precooled solution (-25 ◦C)

of (-)-(1R)-menthyl (S)-p-toluenesulfinate in 170 ml THF through a thick canula. After stirring

was continued for another 20 min, the reaction was quenched by addition of 60 ml of water

and allowed to warm to rt. After extraction with ether and washing twice with water, once

with brine the organic layer was dried over MgSO4 filtered an concentrated in vacuo. The raw

product was purified by flash column chromatography over 350 g of silica gel. First ferrocene

and menthol were washed out using 1:1 diethyl ether/hexane. By changing the eluent to 4:1

diethyl ether/DCM the product could be washed from the column in a second fraction. After

concentration in vacuo the product was dissolved in a minimal amount of DCM/diethylether

3:7 (around 80 ml) and covered with a layer of hexane (40 ml) for crystallisation over two

days. A first fraction crystals where recovered by decanting the mother liquor. The remaining

solution was covered with another layer of hexane (20 ml) to yield a second crop of crystals

over night. The two fractions of crystals where dissolved in a minimal amount of DCM and

precipitated with n-pentane to yield the pure product as a yellow powder by filtration.

Yield: 12 g, 46 %. 1H-NMR (300 MHz, CDCl3): δ 7.52 (d, JHH=7.9 Hz, 2H, CHarom), 7.25 (d,

JHH= 7.9 Hz, 2H, CHarom), 4.61 (m, 1H, CHCp), 4.37 (s, 5H, CHCp′), 4.36 (m, 2H, CHCp), 4.32

(m, 1H, CHCp), 2.37 (s, 3H, CH3). CAS-number: 164297-25-0

Fe

SO(R)-Ferrocenyl t-butyl sulfoxide (15)[78]


A 1 l round bottom schlenk flask was charged with ferrocene (20.0 g,

108 mmol, 2 equiv), t-BuOK (605 mg, 5.44 mmol, 0.1 equiv) and THF

(300 ml) and cooled to –78 ◦C. Addition of t-BuLi (27 ml, 1.9 M in pen-

tane, 0.95 equiv) led to an orange suspension. The reaction mixture was stirred at –78 ◦C for

about 1 h and then allowed to warm to rt and stirred for about 30 min. Meanwhile a solution

of (R)-bis-t-butyl thiosulfinate (10.4 g, 53.8 mmol, 1 equiv) in THF (150 ml) was prepared

99

7 Experimental

in a second 1 l round bottom schlenk flask and cooled to –78 ◦C. The ferrocenyl lithium

suspension was cooled to –78 ◦C and transferred to the thiosulfinate solution using a thick

cannula resulting in a dark red coloured solution. After allowing the solution to warm to

rt and further stirring for 30 min it was quenched with water and extracted with diethyl

ether, washed with water and brine and dried over MgSO4, before concentration in vacuo to

yield the crude product as a yellow powder. Purification by flash column chromatography

yielded the unreacted ferrocene in a first yellow fraction which was eluted with 1:1 diethyl

ether/hexane. After changing the eluent to 4:1 diethyl ether/DCM the product was eluted

in a second orange fraction which after concentration in vacuo yielded the pure product as a

orange solid foam.

Yield: 7.28 g, 47 %. 1H-NMR (300 MHz, CD2Cl2): δ 4.62 (m, 1H, CHCp), 4.40 (m, 1H,

CHCp), 4.38 (m, 1H, CHCp), 4.34 (m, 1H, CHCp), 4.33 (s, 5H, CHCp′), 1.06 (s, 9H, C(CH3)3).

CAS-number: 180293-25-8

Fe

SO(rac)-Ferrocenyl iso-propyl sulfoxide (47)[78]


Ferrocene (4.68 g, 25.2 mmol, 2 equiv) and t-BuOK (141 mg, 1.26 mmol,

0.1 equiv) were put in a 500 ml round bottom schlenk flask and thoroughly

purged with argon. After adding 60 ml of THF the solution was cooled

to –78 ◦C resulting in an orange suspension. t-BuLi (7.9 ml, 1.6 M in pentane, 1 equiv) was

added and the reaction mixture stirred for 30 min before allowing it to warm to rt. While

stirring at rt was prolonged for 30 min, a solution of (R)-bis-iso-propyl thiosulfinate (2.00 g,

12.6 mmol, 1 equiv, 28 %ee) in THF (30 ml) was prepared in a separate 1 l round bottom

schlenk flask and cooled to –78 ◦C. The ferrocenyllithium suspension was cooled to –25 ◦C

using a o-xylene/dry ice bath and transferred via a cannula to the thiosulfinate solution

during 15 min. Stirring was prolonged for another 15 min at –78 ◦C before allowing the

reaction mixture to warm to rt to be stirred for another 30 min before quenching by addition

of water (35 ml). The product was extracted with 60 ml of diethyl ether and the organic layer

washed once with water (30 ml) and twice with brine (30 ml) before drying over MgSO4. The

product was purified by flash column chromatography on silica gel (180 g) using 1:1 diethyl

ether/hexane as an eluent to elute a first coloured fraction containing ferrocene followed by a

4:1 mixture of diethyl ether/DCM to elute the product in a second fraction. The product was

recrystallised from hexane/diethyl ether/DCM 5:2:2 to give the racemic product as yellow

needles.

Yield: 1.29 g, 37 %. 1H-NMR (300 MHz, CDCl3): δ 4.69 (m, 1H, CHCp), 4.40 (m, 2H, CHCp),

100

7.2 Syntheses

4.37 (m, 5H, CHCp′), 4.35 (m, 1H, CHCp), 2.76 (sept, JHH= 6.8 Hz, 1H, CH(CH3)2), 1.17 (d,

JHH= 6.8 Hz, 3H, CH3), 1.09 (d, JHH=6.8 Hz, 3H, CH3). HRMS (Dual MALDI/ESI): m/z

calcd for C13H16FeOS: 276.0266, found 276.0266 [M]+.

Fe

S- Na+Sodium ferrocenylsulfide (45)

C10H9FeNaS, 240.08 g/mol

A 100 ml Schlenk tube was charged with ferrocenylthiol (1.00 g,

4.59 mmol, 1.0 equiv), synthesised according to the literature,[304] and

THF (30 ml). The resulting solution was cooled to –78 ◦C and sodium hydride (0.12 g,

5.05 mmol, 1.1 equiv) was added in small portions resulting in a colour change from orange

to green. Stirring was continued, while the reaction mixture was allowed to warm to rt over

night. The resulting orange suspension was cooled to –78 ◦C before n-pentane (30 ml) was

added and the suspension was filtered to receive the desired product as an orange powder.

Yield: 0.94 g, 85 %. 1H-NMR (300 MHz, (CD3)2CO): δ 4.32 (t, JHH= 1.84 Hz, 2H, CHCp),

4.25 (t, JHH= 1.84 Hz, 2H, CHCp), 4.14 (s, 5H, CHCp′).

Fe

S CF3(Trifluoromethyl)ferrocenylsulfide (10)

C11H9F3FeS, 286.09 g/mol

A 100 ml Schlenk tube was charged with sodium ferrocenylsulfide

(0.50 g, 2.08 mmol, 1.0 equiv) and DCM (20 ml). The resulting solution

was cooled to –78 ◦C and 1-(trifluoromethyl)-1,2-benziodoxol-3-(1H)-one (0.56 g, 1.74 mmol,

1.01 equiv) was added in portions resulting in a colour change from bright yellow to a

greenish yellow. The reaction mixture was stirred over night and allowed to warm to rt

resulting before quenching with water (10 ml). The product was extracted with n-pentane

and the combined organic layers washed with water and brine and dried over MgSO4, before

concentration in vacuo. Flash column chromatography over silica with n-pentane/DCM (5:2)

and concentration in vacuo yielded the product as orange microcrystals.

Yield: 60 mg, 12 %. 1H-NMR (700 MHz, (CDCl3): δ 4.47 (t, JHH= 1.9 Hz, 2H, CHCpCHCS),

4.37 (t, JHH= 1.9 Hz, 2H, CHCHCpCS), 4.23 (s, 5H, CHCp′ .13C{1H}-NMR (176 MHz, CDCl3):

δ 75.6 (s, 2C, CHCpCHCS), 71.1 (s,2C, CHCHCpCS), 69.7 (s, 5C, CHCp′), 67.1 (s, 1C,

CHCCp,quatS). 19F-NMR (188 MHz, CDCl3): δ –45.6 (s, 3F). HRMS (Dual MALDI/ESI): m/z

calcd for C11H9F3FeS: 285.9726, found: 285.9730 [M+].

101

7 Experimental

Fe

PhP

Fe

SSp-tol

O

p-tol

O

(SFc,SFc,SS,SS)-Bis-[2-(p-tolylsulfinyl)ferrocenyl]phenylphosphine

(5)

C40H35Fe2O2PS2, 754.50 g/mol

Diisopropylamine (5.4 ml, 3.9 g, 38 mmol, 2.2 equiv) was dissolved in

20 ml of dry THF in a 100 ml schlenk tube. The solution was cooled

to –78 ◦C, 26 ml of n-BuLi (1.6 M in hexane, 42 mmol, 2.4 equiv) were

added through a canula and the resulting reaction mixture stirred

for 45 min at –78 ◦C. Meanwhile, a 1 l schlenk flask was charged with ferrocenyl sulfoxide 16

(10.3 g, 31.8 mmol, 1.8 equiv) and 200 ml of dry THF and cooled to –78 ◦C. The ready LDA

solution is now added to the ferrocenyl sulfoxide 16 solution resulting in a colour change

from brown to deep red. After stirring for 1 h at -78 ◦C dichlorophenylphosphine (2.4 ml,

3.2 g, 18 mmol, 1 equiv) to the now orange suspension. Stirring was continued at –78 ◦C for

2 h before quenching the reaction mixture with 1 M aqueous NaOH. The aqueous layer was

separated and the organic layer washed with water and brine and dried over MgSO4. The

raw product was adsorbed on silica gel and purified by flash column chromatography. First

two minor yellow fractions where washed out using 2:1:1 diethyl ether/hexane/DCM as an

eluent. After changing the eluent to 1:1 diethyl ether/DCM two more fractions eluted, with

the last containing the desired product. After the solution was evaporated to dryness the

product was obtained as a brown powder.

Yield: 4.7 g, 39 %. 1H-NMR (300 MHz, CDCl3): δ 8.01 (d, JHH=8.3 Hz, 2H, CHPh,ortho),

7.58 (td, JHH=8.3, 1.5 Hz, 2H, CHPh,ortho), 7.43 (d, JHH=8.3 Hz, 2H, CHPh,meta), 7.34 (d,

JHH= 8.3 Hz, 2H, CHPh,ortho), 7.29 (dm, JHH=5.6 Hz, 1H, CHPh,para), 7.23 (dm, JHH=7.8 Hz,

2H, CHPh,meta), 7.08 (dm, JHH=8.3 Hz, 2H, CHPh,meta), 4.55 (m, 1H, CHCp), 4.49 (tm,

JHH= 2.2 Hz, 1H, CHCp), 4.41 (m, 2H, CHCp), 4.34 (s, 1H, CHCp), 4.33 (s, 5H, CHCp′), 4.23

(m, 1H, CHCp), 3.51 (s, 5H, CHCp′), 2.49 (s, 3H, CH3), 2.35 (s, 3H, CH3). 13C-NMR (126 MHz,

CDCl3): δ 142.8, 142.1, 141.9, 140.5, 139.2, 135.1, 134.9, 129.9, 129.6, 128.3 126.3, 125.0,

102.9, 96.3, 81.7, 80.0, 74.4, 74.1, 72.6, 72.1, 71.5, 71.1, 70.3, 69.0, 22.0, 21.8. 31P-NMR

(162 MHz, CD2Cl2): δ –43.2. HRMS (Dual MALDI/ESI): m/z calcd for C40H35Fe2NaO2PS2:

777.0408, found: 777.0394 [M+Na]+.

102

7.2 Syntheses

Fe

SiH

Fe

SSp-tol

O

p-tol

O

Me

(SFc,SFc,SS,SS)-Bis-[2-(p-tolylsulfinyl)ferrocenyl]methylsilane

(34)

C35H34Fe2O2S2Si, 690.55 g/mol

LDA was freshly prepared by dissolving diisopropylamine (0.66 ml,

0.48 g, 4.7 mmol, 2 equiv) in 2 ml of dry THF at –78 ◦C followed

by the addition of 3.2 ml of n-BuLi (1.6 M in hexane, 5.2 mmol,

2.2 equiv) and subsequent stirring for 30 min. The LDA solution was

then added dropwise to a stirred yellow suspension of the ferrocenylsulfoxide 16 (1.51 g,

4.67 mmol, 1 equiv) in 23 ml of THF in a 100 ml schlenk tube. After stirring for an hour

dichloromethylsilane (0.24 ml, ) was added to the reaction mixture resulting in a colour

change from deep orange to yellowish brown. Stirring was prolonged for another hour at

–78 ◦C, before allowing the reaction mixture to warm to rt and quenching with 12 ml of

NaOH(aq.). After extraction with diethyl ether, the organic layer was washed thrice with

water and once with brine, dried over MgSO4 and concentrated in vacuo. Flash column

chromatography with 7:3 n-hexane/diethyl ether eluted first the remaining starting material

and side products. A change of the eluent to 4:1 diethyl ether/DCM yielded the desired

product after concentration in vacuo as a yellow powder.

Yield: 0.53 g, 33 %. 1H-NMR (700 MHz, CDCl3): δ 7.58 (d, JHH= 14.7 Hz, 2H, CHtolyl), 7.57

(d, JHH=14.7 Hz, 2H, CHtolyl) 7.24 (t, JHH= 8.9 Hz, 4H, CHtolyl), 5.30 (q, JHH= 3.8 Hz, 1H,

SiH), 4.54 (m, 1H, CHCp), 4.49 (m, 1H, CHCp), 4.44 (m, 1H, CHCp), 4.40 (m, 1H, CHCp),

4.32 (s, 5H, CHCp′), 4.28 (m, 1H, CHCp), 4.27 (s, 5H, CHCp′), 2.42 (s, 3H, CH3), 2.41 (s, 3H,

CH3), 1.10 (d, JHH= 3.8 Hz, 3H, SiCH3). 13C{1H}-NMR (176 MHz, CDCl3): δ 142.2 (s, 1C

Ctolyl,quatS), 141.4 (s, 1C Ctolyl,quatS), 141.0 (s, 1C Ctolyl,quatMe), 140.9 (s, 1C Ctolyl,quatMe), 129.3

(s, 4C, CHtolyl), 125.6 (s, 4C, CHtolyl), 98.4 (s, 1C, CCp,quat), 97.9 (s, 1C, CCp,quat), 79.9 (s, 1C,

CHCp), 78.1 (s, 1C, CHCp), 72.6 (s, 1C, CHCp), 72.5 (s, 1C, CHCp), 70.9 (s, 1C, CHCp), 70.5 (s,

1C, CHCp) 70.3 (s, 5C, CHCp′), 70.2 (s, 5C, CHCp′), 69.6 (s, 1C, CCp,quat), 69.4 (s, 1C, CCp,quat),

21.4 (s, 1C, (CH)2CCH3), 21.3 (s, 1C, (CH)2CCH3), –2.05 (s, 1C, SiCH3). 29Si{1H}-NMR

(60 MHz, CDCl3): δ –21.5 (s, 1Si). MS (ESI): m/z calcd for C35H34Fe2O2S2Si: 690.05, found:

689.04 (100 %), 690.04 (47 %), 691.05 (23 %) [M – H]+.

103

7 Experimental

FePt SCl

O

P

Fe

SOCl

Di-κ1-chloro(κ2-(SFc,SFc,SS,SS)-Bis-

[2-(p-tolylsulfinyl)ferrocenyl]-

phenylphosphine)platinum(II) (43)

C40H35Cl2Fe2O2PPtS2, 1020.49 g/mol

A 50 ml Schlenk tube was charged with dichloro-1,5-

cyclooctadieneplatinum(II) (162 mg, 0.433 mmol,

1 equiv), sulfoxophosphine ligand 5 (327 mg,

0.433 mmol, 1 equiv) and DCM (20 ml) and the re-

sulting reaction mixture was stirred over night at rt. Then

the solvent was reduced reduced in vacuo to give about 5 ml of solution, which was covered

with a layer of n-hexane in order to precipitate the product as a dark yellow powder.

Yield: 0.37 mg, 83 %. 1H-NMR (400 MHz, CD2Cl2): δ 8.46 (d, JHH = 8.0 Hz, 2H,

S(1)CCHarom), 8.22 (dm, JPH = 13.8 Hz, 2H, PCCHPh), 8.04 (d, JHH = 8.5 Hz, 2H,

S(2)CCHarom), 7.70 (m, 2H, CHPh,meta), 7.70 (m, 1H, CHPh,para), 7.62 (d, JHH = 8.0 Hz,

2H, S(1)CCHCHarom), 7.42 (d, JHH =8.5 Hz, 2H, S(2)CCHCHarom), 5.26 (m, 1H, CHC p on

Fe(1)), 4.85 (m, 1H, CHC p on Fe(1)), 4.77 (m, 1H, CHC p on Fe(2)), 4.70 (m, 1H, CHCHC pCH

on Fe(2)), 4.53 (m, 1H, CHCHC pCH on Fe(1)), 4.36 (m, 1H, CHC p on Fe(1)), 4.36 (s, 5H,

CHCp′ on Fe(2)), 3.45 (s, 5H, CHCp′ on Fe(1)), 2.59 (s, 3H, S(1)(C6H4)CH3), 2.47 (s, 3H,

S(2)(C6H4)CH3) (for labeling cf. Chapter 3.4). 13C{1H}-NMR (100 MHz, CD2Cl2): δ 145.5

(s, 1C, S(1)Carom,quat), 142.2 (s, 1C, CH3CCH2CH2CS(2)), 141.9 (s, 1C, S(2)Carom,quat), 139.3

(s, 1C, CH3CCH2CH2CS(1)), 133.1 (s, 2C, PCCH), 129.9 (s, 2C, S(1)CCHCH), 129.7 (s, 2C,

PCCHCH), 129.6 (s, 2C, S(2)CCHCH), 129.1 (s, 1C, PCCHCHCH), 127.8 (s, 2C, S(1)CCH),

125.9 (s, 2C, S(2)CCH), 100.8 (s, 1C, CCp,quat on Fe(2)), 81.7 (s, 1C, CCp,quat on Fe(1)), 82.0

(s, 1C, CHCp on Fe(1)), 76.4 (s, 1C, CHCp on Fe(2)), 72.7 (s, 1C, CHCHCpCH on Fe(2)), 71.0

(s, 1C, CHCp on Fe(2)), 68.5 (s, 1C, CHCp on Fe(1)), 65.6 (s, 1C, CHCp on Fe(1)), 21.9 (s,

1C, S(1)(C6H4)CCH3), 21.6 (s, 1C, S(2)(C6H4)CCH3. 31P{1H}-NMR (162 MHz, CD2Cl2): δ

21.06 HRMS (MALDI): m/z calcd for C40H35Cl2Fe2NaO2PPtS2: 1041.9439, found: 1041.9436

[M+Na]+.

104

7.2 Syntheses

FePd SCl

O

P

Fe

SOCl

Di-κ1-chloro(κ2-(SFc,SFc,SS,SS)-Bis-

[2-(p-tolylsulfinyl)ferrocenyl]-

phenylphosphine)palladium(II) (42)

C40H35Cl2Fe2O2PPdS2, 931.82 g/mol

A 50 ml Schlenk tube was charged with dichloro-1,5-

cyclooctadienepalladium(II) (182 mg, 0.636 mmol,

1 equiv), sulfoxophosphine ligand 5 (499 mg,

0.661 mmol, 1.05 equiv) and THF (20 ml) and the

resulting reaction mixture was stirred for 24 h at rt. The

solution was filtered and concentrated to dryness in vacuo to give a yellow powder, which was

redissolved in a minimal amount of THF and the resuling solution was covered with a layer

of n-hexane to precipitate the desired product.

Yield: 462 mg, 78 %. 1H-NMR (400 MHz, CDCl3): δ 8.42 (d, JHH =7.5 Hz, 2H, S(1)CCHarom),

8.22 (dm, JPH =10.3 Hz, 2H, PCCHPh), 8.07 (d, JHH =7.7 Hz, 2H, S(2)CCHarom), 7.65 (m,

2H, CHPh,meta), 7.65 (m, 1H, CHPh,para), 7.53 (d, JHH =7.5 Hz, 2H, S(1)CCHCHarom), 7.32

(d, JHH = 7.7 Hz, 2H, S(2)CCHCHarom), 4.99 (m, 1H, CHC p), 4.82 (m, 1H, CHC p), 4.78

(m, 1H, CHC p), 4.63 (m, 1H, CHC p), 4.47 (s, 5H, CHCp′), 4.43 (m, 1H, CHC p), 4.31 (m,

1H, CHC p), 3.51 (s, 5H, CHCp′), 2.53 (s, 3H, CH3), 2.47 (s, 3H, CH3) (for labeling cf.

Chapter 3.4). 31P{1H}-NMR (121 MHz, CD2Cl2): δ 43.5. HRMS (MALDI): m/z calcd for

C40H35Fe2NaO2PPdS2: 859.9550, found: 859.9561 [M – 2Cl]+.

Rhodium complex of Bis-[2-(p-tolylsulfinyl)ferrocenyl]-phenylphosphine (48)

A 50 ml Schlenk tube was charged with bis(chlorocyclooctadienerhodium(I)) (170 mg,

0.345 mmol, 1 equiv) and sulfoxophosphine ligand 5 (553 mg, 0.733 mmol, 2.1 equiv). 25 ml

of dry DCM were added an the resulting solution stirred over night at rt. The volume of the

solution was reduced in vacuo to about 10 ml and covered with a layer of n-hexane in order

to slowly precipitate a brown powder, that was used in Miyaura-Hayashi reaction (vide infra).

Yield: 551 mg. 31P{1H}-NMR (202 MHz, d8-THF): δ 25.5, 56.3 (d, JPRh= 167.1 Hz). HRMS

(MALDI): m/z calcd for C40H35Fe2O2PRhS2: 856.9570, found: 859.9564 [5+Rh].

105

7 Experimental

Fe

FeP

P

Ph

Ph2PPh2

(RFc,RFc)-Bis-(2-diphenylphosphino-ferrocenyl)phenylphosphine

(4)

(SFc,SFc,SS,SS)-Bis-[2-(p-tolylsulfinyl)ferrocenyl]phenylphosphine

(5) (0.93 g, 1.2 mmol, 1 equiv) was dissolved in THF (40 ml) and

cooled to –78 ◦C. 0.72 ml of t-BuLi (1.9 M in pentane, 1.4 mmol,

1.1 equiv) were added and the reaction mixture was stirred at –78 ◦C for an hour before the

addition of chlorodiphenylphosphine (0.27 ml, 0.33 g, 1.5 mmol, 1.2 equiv). After stirring

for another hour at –78 ◦C the reaction mixture was allowed to warm to rt and 8 ml of 1 M

aqueous NaOH were added. The quenched reaction mixture was extracted with DCM and

the combined organic layers were washed with water and brine and dried over MgSO4. The

raw product was dissolved in DCM, filtered through a silica pad and concentrated in vacuo.

The raw product (0.89 g, 1.1 mmol, 1,equiv) was dissolved in dry THF and 0.68 ml of t-BuLi

(1.9 M in pentane, 1.2 mmol, 1.1 equiv) were added at –78 ◦C. After one hour of stirring,

chlorodiphenylphosphine (0.25 ml, 1.3 mmol, 1-2 equiv) was added and the mixture stirred

for anouther hour at –78 ◦C. The reaction was allowed to warm to rt and subsequently

quenched by the addition of 8 ml of 1 M aqueous NaOH. After extraction with DCM the

combined organic layers were washed with water and brine and dried over MgSO4 before

concentration in vacuo. Purification by flash column chromatography over silica yielded a

first coloured fraction by using DCM/n-hexane 5:1 as an eluent. A second coloured fraction

was obtained with pure DCM as eluent, while a third fraction containing starting material

was eluted by using DCM/diethyl ether 1:1. The second fraction was further purified using

preparative HPLC (OD-H, n-hexane/i-PrOH 95:5, 0.7 ml/min) to give the desired product in

a second fraction (tR: 7.88 – 8.49 min) with a slight impurity of (RFc)-(2-diphenylphosphino-

ferrocenyl)-ferrocenylphenylphosphine 35. Compound 35 was obtained in a third fraction

(tR: 8.51 – 9.05 min).

(RFc,RFc)-Bis-(2-diphenylphosphino-ferrocenyl)phenylphosphine (4): Yield: <50 mg,

<5 %. HRMS (ESI): m/z calcd for C50H41Fe2P3: 846.1120, found: 846.1269.

(RFc)-(2-diphenylphosphino-ferrocenyl)-ferrocenylphenylphosphine (35): Yield: 30 mg,

3.8 %. 1H-NMR (400 MHz, CDCl3): δ 7.56 (m, 2H, CHPh), 7.38 (m, 1H, CHPh,para), 7.36

(m, 2H, CHPh), 7.34 (m, 2H, CHPh on the bisferrocenyl phosphine), 7.09 (t, JHH= 6.9 Hz,

1H, CHPh,para on the bisferrocenyl phosphine), 7.03 (t, JHH=7.2 Hz, 2H, CHPh on the bisfer-

rocenyl phosphine) 6.94 (t, JHH= 7.0 Hz, 1H, CHPh,para), 6.81 (t, JHH= 7.0 Hz, 2H, CHPh),

6.76 (t, JHH= 7.1 Hz, 2H, CHPh), 4.67 (m, 1H, CHCp on ferrocenyl), 4.43 (m, 1H, CHCp on

ferrocenylphosphine), 4.37 (m, 1H, CHCp on ferrocenyl), 4.32 (m, 1H, CHCp on ferrocenyl),

4.23 (m, 1H, CHCp on ferrocenylphosphine), 4.08 (s, 5H, CHCp′), 3.96 (m, 1H, CHCp on

106

7.2 Syntheses

ferrocenylphosphine), 3.94 (s, 5H, CHCp′), 3.92 (m, 1H, CHCp on ferrocenyl). 31P{1H}-NMR

(162 MHz, CDCl3): δ –22.6 (d, JPP= 87.6 Hz, 1P, FcPPh2), –35.7 (d, JPP= 87.6 Hz, 1P, Fc2PPh).

HRMS (ESI): m/z calcd for C38H32Fe2P2: 662.0678, found: 662.0821 [M]+.

Fe

PFe

Ph2P PPh2

Cy

Ni

F

+

BF4-

[κ1-Fluorido(κ3-Pigiphos)nickel(II)]tetrafluoroborate

(44)

C54H55Fe2P3, 908.65 g/mol

A 100 ml Schlenk tube was charged with

Pigiphos (1.0 g) and [Ni(COD)2] (310 mg).

12 ml of toluene were added resulting in a

dark red solution and the reaction mixture

was stirred for 1 h at rt. Then 1-fluoro-2,4,6-

trimethylpyridinium tetrafluoroborate (360 mg) was added to the reaction mixture before

stirring for another 24 h at rt. The solvent was evaporated in vacuo to give the raw product

as a deep red solid. Portions of the raw product were redissolved in DCM filtered through a

syringe filter and the resulting saturated DCM solution was covered with a layer of n-pentane

for crystallisation to get purer product suitable for analysis.

Yield: 19F-NMR (376 MHz, CDCl3): δ –151 (s, 4F, BF−4 ), –323 (b, 1F, NiF). 31P{1H}-NMR

(162 MHz, CDCl3): δ 75.4 (q, J= 76.2 Hz, 1P, CyP), 13.2 (dtb, J=272.3, 56.0 Hz, 1P, PPh2),

7.3 (ddd, J= 272.5, 79.3, 55.9 Hz).

FeFe

SSO

O

(RFc,RFc,RS,RS)-Bis-[2-(t-butylsulfinyl)ferrocene] (6)[255]

C28H34Fe2O2S2, 578.39 g/mol

A 250 ml round bottom schlenk flask was charged with

ferrocenylsulfoxide 15 (7.28 g, 25.1 mmol, 2 equiv) and

60 ml of THF to give a dark orange solution, which then was

cooled to –78 ◦C. 16 ml of n-BuLi (1.6 M in hexane, 25 mmol,

2 equiv) were added slowly to the reaction mixture resulting in a darkening of the reaction

mixture. After 10 min of stirring the now slightly green reaction mixture was allowed to

warm to rt and stirred for another 20 min before cooling again to –78 ◦C for the addition of

CuCN (1.10 g, 12.5 mmol, 1 equiv). The reaction mixture was then warmed to about –30 ◦C

using a o-xylene/dry ice cooling bath and stirred for 20 min. Afterwards oxygen was bubbled

through the solution at –78 ◦C for 10 min resulting in a colour change to deep red and the

reaction mixture was stirred under oxygen atmosphere (1 bar) over night allowing it to warm

107

7 Experimental

to rt. The reaction was quenched by adding 70 ml of water, extracted with DCM and the

organic layer washed with brine before drying over MgSO4 and concentrating in vacuo. Flash

column chromatography using 1:4 diethyl ether/hexane yielded two fractions, with the first

fraction containing what seems to be the Sa atropisomer of the product in a yield of 0.28 g.

After a change of the eluent to 1:1 DCM/diethyl ether the product was eluted in a fourth

fraction yielding a dark orange solid after vaporisation of the solvent. Crystals for X-ray where

obtained by putting a layer of n-pentane over a concentrated solution of the product in DCM.

(RFc,RFc,Sa,RS,RS)-Bis-[2-(t-butylsulfinyl)ferrocene] (6a): Yield: 0.28 g (of the acid with

unknown counterion), 4 %. 1H-NMR (700 MHz, CD2Cl2): δ 7.79 (s, 2H, acidic protons,

cf. Chapter 4.2), 4.35 (s, 10H, CHCp′), 4.31 (m, 2H, CHCp), 4.00 (m, 2H, CHCp), 3.97 (m,

2H, CHCHCpCH), 1.21 (s, 18H, C(CH3)3). 13C{1H}-NMR (176 MHz, CD2Cl2): δ 125.7 (s,

2C, CCp,quat), 70.9 (s, 10C, CHCp′), 65.6 (s, 2C, CCp,quat), 62.6 (s, 2C, CHCp), 61.9 (s, 2C,

CHCp), 58.9 (s, 2C, CHCHCpCH), 56.7 (s, 2C, C(CH3)3), 22.2 (s, 6C, C(CH3)3). HRMS (Dual

MALDI/ESI): m/z calcd for C28H34Fe2O2S2: 578.0694, found: 578.0696 [M]+.

(RFc,RFc,Ra,RS,RS)-Bis-[2-(t-butylsulfinyl)ferrocene] (6b): Yield: 4.29 g, 59 %. 1H-NMR

(300 MHz, CDCl3): δ 5.48 (dd, JHH=2.7, 1.6 Hz, 2H, SCC(C)CHCp), 4.58 (s, 10H, CHCp′),

4.48 (t, JHH=2.7 Hz, 2H, CHCHCpCH), 4.41 (dd, JHH=2.7, 1.6 Hz, 2H, SCCHCp), 1.00

(s, 18H, C(CH3)3). 13C-NMR (176 MHz, CD2Cl2) δ 86.3 (s, 2C, CCp,quat), 84.9 (s, 2C,

CCp,quat), 77.6 (s, 2C, SCC(C)CHCp), 72.4 (s, 2C, SCCHCp), 71.2 (s, 10C, CHCp′), 69.0 (s,

2C, CHCHCpCH), 55.6 (s, 2C, C(CH3)3), 23.7 (s, 6C, C(CH3)3). HRMS (Dual MALDI/ESI):

m/z calcd for C28H34Fe2O2S2: 578.0694, found: 578.0694 [M]+. Mp: 188 ◦C. Bp: 198 ◦C

(decomp).

FeFe

SS

(Ra,RFc,RFc)-Bis-[2-(t-butylsulfanyl)ferrocene] (7)

C28H34Fe2S2, 546.39 g/mol

Sulfoxide 6 (505 mg, 0.864 mmol, 1 equiv) was dissolved in

approximately 18 ml of dry toluene. 2.6 ml of triethyl amine

(20-fold excess) and 2.7 ml trichlorosilane (40-fold excess)

were added and the resulting reaction mixture was refluxed at 110 ◦C for 15 h before carefully

quenching with 34 ml of a 10 % aqueous NaOH solution. After extraction with DCM (twice

with 35 ml), drying of the combined organic layers over MgSO4 and concentration in vacuo,

the raw product was purified by flash column chromatography over 30 g of silica (1:50

diethyl ether/n-pentane) yielding the pure product in a first coloured fraction, with the

second coloured fraction containing the starting material. After vaporisation of the solvent

the product was obtained as a dark orange crystalline solid. Crystals for x-ray were grown

108

7.2 Syntheses

from a concentrated DCM solution, which was covered with a layer of n-pentane.

Yield: 160 mg, 34 %. 1H-NMR (300 MHz, CDCl3): δ 5.09 (dd, JHH= 2.7, 1.6 Hz, 2H, CHCp),

4.40 (m, 4H, CHCp), 4.31 (s, 10H, CHCp′), 0.96 (s, 18H, C(CH3)3). 13C{1H}-NMR (75 MHz,

CDCl3): δ 89.2 (s, 2C, CCp,quat), 77.2 (s, 2C, CCp,quat), 76.9 (s, 2C, CHC p), 72.7 (s, 2C, CHCp),

70.7 (s, 2C, CHCp), 45.8 (s, 2C, C(CH3)3), 30.9 (s, 6C, C(CH3)3). HRMS (Dual MALDI/ESI):

m/z calcd for C28H34Fe2S2: 546.0796, found: 546.0795 [M]+. Mp: 147 ◦C.

SO

Fe

Sn

(RFc,SS)-(p-Tolylsulfinyl)-2-(tri-n-butylstannyl)ferrocene (41)[75]

C29H42FeOSSn, 613.27 g/mol

LDA was freshly prepared by reacting 1.3 ml of diisopropylamine

() with 5 ml n-BuLi in 22 ml of THF for 15 min at –78 ◦C. Mean-

while a 250 ml schlenk flask was charged with sulfoxide 16 (2.33 g,

7.19 mmol, 1 equiv) and THF (44 ml). The LDA solution was added to

the sulfoxide solution by cannula and the resulting reaction mixture

stirred at –78 ◦C for 20 min. 2.4 ml of tri-n-butylstannyl chloride

(2.8 g, 8.7 mmol, 1.2 equiv) were added to the solution and the resulting reaction mixture

was stirred for 1 h at –78 ◦C before allowing it to warm to rt. Stirring was continued at rt

for 2 h before quenching the solution with 15 ml of a 1 M aqueous solution of NaOH. The

product was extracted with diethyl ether and the combined organic layers washed twice with

water and once with brine before drying over MgSO4. Flash column chromatography over

silica gel (7:3 hexane/diethyl ether) eluted the product in a second coloured fraction. After

evaporation of the solvents in vacuo the product was obtained as a red viscous oil.

Yield: 4.14 g, 94 %. 1H-NMR (300 MHz, CDCl3): 7.55 (d, JHH=8.1 Hz, 2H, CHarom), 7.27

(d, JHH= 8.1 Hz, 2H, CHarom), 4.45 (t, JHH= 2.4 Hz, 1H, CHCp), 4.25 (m, 2H, CHHH) 4.21 (s,

5H, CHCp′), 2.39 (s, 3H, Carom,quatCH3), 1.66 – 1.20 (m, 12H, CH2), 1.19 – 1.02 (m, 6H, CH2),

0.98 – 0.82 (m, 9H, CH2CH3).

109

7 Experimental

BrFe

Sn

(RFc)-(Bromo)-2-(tri-n-butylstannyl)ferrocene (9)

C22H35BrFeSn, 553.98 g/mol

The ferrocenylstannane 41 (1.00 g, 1.63 mmol, 1 equiv) was dissolved

in 16 ml of diethyl ether and cooled –78 ◦C before the addition of

0.94 ml of t-BuLi (1.9 M in pentane, 1.8 mmol, 1.1 equiv). After

1 h of stirring the solution was allowed to warm to rt for 30 min

and subsequently cooled again to –78 ◦Cfor the addition of 1,2-

dibromotetrachloroethane (1.06 g, 3.26 mmol, 2 equiv). The reaction mixture was allowed to

warm slowly to rt and stirred for another 3 h before quenching with water. After extraction

with diethyl ether, washing with water and brine and drying over MgSO4, the crude product

was concentrated in vacuo and purified by flash column chromatography with n-pentane

over silica gel. A second column under the same conditions yielded the desired product in a

mixture with tri-n-butylstannylferrocene in an approximately 4:1 ratio (determined by NMR)

as a dark yellow oily substance.

Yield: 450 mg (NMR-yield), 50 %. 1H-NMR (300 MHz, CDCl3): δ 4.54 (dd,JHH=2.3 Hz,

1.2 Hz, 1H, CBrCH), 4.21 (t, JHH= 2.3 Hz, 1H, CHCHCH), 4.16 (s, 5H, CHCp′), 3.91 (dd,

JHH= 2.3 Hz, 1.2 Hz, 1H CSnCH), 1.70 – 1.46 (m, 6H, CH2), 1.45 – 1.28 (m, 6H, CH2),

1.21 – 1.01 (m, 6H, CH2), 0.96 – 0.86 (t, JHH= 7.3 Hz, 9H, CH3). 13C{1H}-NMR (75 MHz,

CDCl3): δ 86.1 (1C, CBr), 73.5 (1C, C(SnBu3)CH), 72.9 (1C, CSnBu3), 72.3 (1C, CBrCH),

70.4 (5C, CHCp′), 69.4 (1C, CHCHCH), 29.2 (3C, CH2), 27.4 (3C, CH2), 13.7 (3C, CH3), 10.7

(3C, CH2). HRMS (EI): m/z calcd for C22H35BrFeSn: 554.0294, found: 554.0298 [M]+.

FeFe

Bu3SnBr2-((SFc)-2”-Bromoferrocenyl)-1-((RFc)-tri-n-

butylstannyl)ferrocene (49)[282]

C32H43BrFe2Sn, 737.99 g/mol

The CuI used in this reaction was first purified following a literature

procedure.[305] A 20 ml Schlenk tube was charged with bromostan-

nyl ferrocene 9 (280 mg, 0.505 mmol, 1 equiv), CuI (19.3 mg, 0.101 mmol, 0.2 equiv),

triphenylarsine (61.9 mg, 0.202 mmol, 0.4 equiv) and 4 ml of N-methylpyrrolidinone. The

solution was degassed before the addition of 5 mg of 10 % palladium on activated carbon

(0.005 mmol, 0.01 equiv) and stirred for 24 h at 95 ◦C. After diluting the mixture with 5 ml

ethyl acetate it was poured into 30 ml of a saturated aqueous sodium fluoride solution and

stirred for another 30 min before filtering it through a sand pad. The aqueous layer of the

filtrate was extracted twice with ethyl acetate (10 ml) and the combined organic layers poured

into a fresh saturated sodium fluoride solution (60 ml) and stirred for another 30 min. The

110

7.2 Syntheses

mixture is than again filtered through a sand pad and the sand pad rinsed with ethyl acetate

(10 ml). The organic layer was separated from the aqueous layer and washed three time with

water (10 ml) and twice with brine (10 ml) before drying it over MgSO4. The dried solution

was concentrated in vacuo and seperated by flash column chromatography over silica using

n-pentane as eluent.

Yield: traces. HRMS (Dual MALDI/ESI): m/z calcd for C32H43BrFe2Sn: 738.0262, found:

738.0251.

Fe

PPhPh

H3B

SO

(SFc,SS)-(p-Tolylsulfinyl)-2-[diphenylphosphino(borane)]ferrocene

(33)[75]

C29H28BFeOPS, 522.23 g/mol

Ferrocenylsulfoxide 16 (1.83 g, 5.83 mmol, 1 equiv) was dissolved in 35 ml

of THF and cooled to –78 ◦C. LDA that was freshly prepared by adding

n-BuLi (4.0 ml, 1.6 M in hexane, 6.4 mmol, 1.1 equiv) to a solution of

diisopropylamine (1.0 ml, 7.1 mmol, 1.2 equiv) in THF (17 ml) at –78 and

stirred for 10 min was added then added to the solution. After stirring for one hour at –78 ◦C

1.3 ml of chlorodiphenylphosphine (1.6 g, 7.3 mmol, 1.2 equiv) were added to the reaction

mixture and stirring was continued for another hour before addition of borane THF complex

solution (15.5 ml, 1 M in THF, 15.5 mmol, 2.65 equiv) and stirring at rt over night. The

reaction was quenched by the addition of water (10 ml), extracted with ether and the organic

layer washed with water and brine. Flash column chromatography over silica gel using ether

as eluent and evaporation of the solvent yielded the product as a yellow crystalline solid.

Yield: 1.96 g, 64 %. 1H-NMR (300 MHz, CDCl3): δ 7.80 – 7,1 (m, 4H, CHPh), 7.60 (d,

JHH= 8.1 Hz, 2H, CHarom), 7.49 – 7.35 (m, 6H, CHPh), 7.27 (d, JHH=8.1 Hz, 2H, CHarom), 4.52

(m, 1H, CHCp), 4.47 (m, 1H, CHCp), 4.32 (m, 1H, CHCp), 4.06 (m, 5H, CHCp′), 2.37 (s, 3H,

CH3), 1.77 – 0.68 (b, 3H, BH3). 31P{1H}-NMR (121.5 MHz, CDCl3): δ 16.6 (s, 1P).

BrFe

PPhPh

H3B(RFc)-Bromo-2-[diphenylphosphino(borane)]ferrocene (50)

C22H21BBrFeP, 462.94 g/mol

Ferrocenylsulfoxide 33 (1.96 g, 3.75 mmol, 1 equiv) was dissolved in di-

ethyl ether (38 ml), cooled to –78 ◦C and 2.6 ml of t-BuLi (1.6 M in pentane,

4.16 mmol, 1.1 equiv) were added to the resulting solution. After 1 h of stir-

ring 1,2-dibromotetrachloroethane (2.56 g, 7.83 mmol, 2 equiv) was added

and the resulting reaction mixture stirred over night allowing it to warm to rt. Quenching

with water and extraction with ether, followed by washing the combined organic layers with

111

7 Experimental

water and brine and drying it over MgSO4 yielded the crude product after evaporation of

the solvents in vacuo. Purification by flash column chromatography using diethyl ether as an

eluent on silica yielded the product in a mixture with [diphenylphosphino(borane)]ferrocene,

which ratio varied between 3:1 and 1:3 depending on the experiment, as a orange solid.

Altenative methods used halon 2402 (2 equiv) or 1,2-dibromoethane (3 equiv) as bromina-

tion agents without any greater impact on the yield. In one case purification was performed

on a Teledyne ISCO CombiFlash®Rf100 with cyclohexane/triethylamine 100:1 as eluent. But

no seperation of the desired product from the [diphenylphosphino(borane)]ferrocene could

be achieved.

Yield: 320 mg (NMR-yield), 18 % (best run yielded 50 %). 31P{1H}-NMR (121.5 MHz,

CDCl3): δ –18.5 (b, 1P, FcP(BH3)Ph2).

BrFe

PPhPh(RFc)-Bromo-2-(diphenylphosphino)ferrocene (40)

C22H18BrFeP, 449.10 g/mol

A mixture of [diphenylphosphino(borane)]ferrocene and ferrocene 50

(1.05 g, 2.60 mmol of phosphinoboranes of which 0.650 mmol are desired

starting material) in a 3:1 ratio were dissolved in 30 ml of degassed

diethylamine (100-fold excess) and refluxed at 65 ◦C under argon overnight. Evapora-

tion of the solvent in vacuo and filtration over silica gel with diethyl ether yielded the

desired product 40 in a 1:3 ratio with (diphenylphosphino)ferrocene as an orange solid.

Although a visible seperation of the to substances can be achieved on TLC (40:2:1 n-

pentane/diethyl ether/triethylamine) purification by flash column chromatography was

proved impractical. For analytics and full characterisation a seperation of the mixture was

achieved by preparatory HPLC using 99:1 n-hexane/i-PrOH on an OJ-column at a flow rate of

0.7 ml/min.

Yield: 860 mg, 85 %, of which 248 mg belong to compound 40. 1H-NMR (300 MHz, CDCl3):

δ 7.55 (m, 2H, CHPh), 7.40 (m, 3H, CHPh), 7.27 (m, 3H, CHPh), 7.18 (m, 2H, CHPh), 4.68 (dt,

JHH= 2.6, 1.4 Hz, 1H, CHCp), 4.24 (td, JHH= 2.6, 0.7 Hz, 1H, CHCp), 4.16 (s, 5H, CHCp′), 3.64

(dd, JHH= 2.6, 1.7 Hz, 1H, CHCp). 31P{1H}-NMR (121 MHz, CDCl3): δ –20.2 (s, 1P, FcPPh2).

HRMS (EI): m/z calcd for C22H18BrFeP: 447.9679, found: 447.9675 [M]+.

112

7.2 Syntheses

Fe

NBr

(SFc)-1-Bromo-2-[(RN)-(1-N,N-dimethylamino)ethyl]ferrocene (51)[87]

C14H18BrFeN, 336.05 g/mol

A solution of (RN)-(+)-[1-(dimethylamino)ethyl]ferrocene (8.10 g,

31.5 mmol, 1 equiv) in diethyl ether (45 ml) was cooled to –78 ◦C before

dropwise addition of 16.6 ml of t-BuLi (1.9 M in pentane, 31.5 mmol,

1 equiv). The reaction mixture was stirred for 30 min at –78 ◦C and then allowed to

warm to rt for further stirring for 1 h. After being cooled to –78 ◦C, 4.71 ml of 1,2-

dibromotetrafluoroethane (10.2 g, 39.4 mmol, 1.25 equiv) were added dropwise to the

reaction mixture and stirring prolonged at –78 ◦C for an hour before allowing the solution to

warm to rt and stirring it over night. The reaction was quenched by addition of a saturated

aqueous solution of NaHCO3 and the aqueous layer extracted with diethyl ether. The

combined organic layer were washed twice with water and once with brine before drying

over MgSO4 and evaporation of the solvent in vacuo. Purification by filtration over silica gel

using a mixture of 2:1 ethyl acetate/n-hexane with 1 % of triethylamine and evaporation of

the solvents in vacuo yielded the product as an orange powder.

Yield: 10.0 g, 94 %. [α]20D = +9.6 (c= 1.002, CHCl3) 1H-NMR (300 MHz, CDCl3): δ 4.54

(m, 1H, CHCp), 4.16 (s, 5H, CHCp′), 4.13 (m, 1H, CHCp), 4.10 (m, 1H, CHCp), 3.75 (q,

JHH=6.9 Hz, 1H, CHCH3), 2.13 (s, 6H, N(CH3)2), 1.52 (d, JHH= 6.9 Hz, 3H, CHCH3).

CAS-number: 205746-95-8

Fe

NBr

I-

(SFc)-1-Bromo-2-[(RN)-(1-N,N,N-trimethylammonium)ethyl]ferrocene

iodide (52)

C15H21BrFeIN, 477.99 g/mol

A 50 ml Schlenk tube was charged with ferrocene 51 (2.00 g, 5.95 mmol,

1 equiv) and THF (20 ml) and the resulting solution cooled to 0 ◦C. After

addition of 1.7 ml of iodomethane (3.9 g, 27 mmol, 4.6 equiv) the solution was stirred for

an hour while the product was formed as a solid precipitating out of solution. The reaction

mixture was dilluted with diethyl ether (20 ml) and the yellow solid product filtered of and

washed with further portions of diethyl ether before drying it over night in vacuo.

Yield: 2.32 g, 82 %. 1H-NMR (300 MHz, CDCl3): δ 4.71 (dd, JHH= 2.6, 1.3 Hz, 1H, CHCp),

4.54 (q, JHH=6.8 Hz, 1H, CHCH3), 4.53 (dd, JHH= 2.6, 1.3 Hz, 1H, CHCp), 4.48 (dd,

JHH= 2.6 Hz, 1H, CHCp), 4.29 (s, 5H, CHCp′), 3.28 (s, 9H, N(CH3)3), 2.14 (d, JHH= 6.8, 3H,

CHCH3).

113

7 Experimental

FeBr

(SFc)-1-Bromo-2-vinylferrocene (53)

C12H11BrFe, 290.96 g/mol

A seperation funnel was charged with 30 ml of DCM and 30 ml of a saturated

aqueous solution of potassium carbonate and iodide salt 52 (1.32 g, 2.76 mmol,

1 equiv) was added. The funnel was shaken for 10 min with repeated release of

pressure. As formation of CO2 ceased the organic layer was collected and the aqueous layer

extracted twice with DCM (2 x 20 ml). The combined organic layers where dried over MgSO4

and concentrated in vacuo giving a waxy solid substance as crude product. The crude product

was distilled of at 100 ◦C in vacuo yielding the product as a red-orange liquid.

Yield: 626 mg, 78 %. 1H-NMR (300 MHz, CDCl3): δ 6.61 (dd, JHH=17.6, 11.0 Hz, 1H, (Z)-

CHHv iny l), 5.48 (dd, JHH= 17.6, 1.6 Hz, 1H, (E)-CHHv iny l), 5.20 (dd, JHH= 11.0, 1.6 Hz,

1H, CHv iny lCH2), 4.47 (ddd, JHH=8.8, 2.6, 1.3 Hz, 2H, CHCp), 4.20 (tm, JHH= 2.6 Hz, 2H,

CHCp), 4.14 (s, 5H, CHCp′). HRMS (MALDI): m/z calcd for C12H11FeBr: 289.9388, found:

289.9391.

114

7.2 Syntheses

7.2.2 Substrates and Catalyses

OAc(rac)-(E)-1,3-Diphenylallyl acetate[306]

C17H16O2, 252.33 g/mol

(rac)-(E)-3-hydroxy-1,3-diphenylpropene (2.45 g, 11.7 mmol,

1 equiv), acetic anhydride (1.3 ml, 1.4 g, 14 mmol, 1.2 equiv),

triethylamine (2.9 ml, 2.1 g, 21 mmol, 1.8 equiv) and 4-dimethylaminopyridine (7.1 mg,

0.058 mmol, 0.005 equiv) were dissolved in 25 ml of THF at 0 ◦C using an ice bath. After

stirring for an hour the ice bath was removed and stirring was continued at rt over night

before evaporation of the solvent. The product was redissolved in diethyl ether and washed

with a saturated aqueous NH4Cl solution before drying over MgSO4 and concentration in

vacuo. Flash column chromatography (4:1 hexane/ethyl acetate) over silica gel yielded the

product as a colourless oil

Yield: 2.74 g, 92.9 %. 1H-NMR (300 MHz, CDCl3): δ 7.6 – 7.33 (m, 10H, CHarom), 6.84 (d,

JHH= 15.9 Hz, 1H, CHallyl), 6.69 (d, JHH= 6.6 Hz, 1H, CHallyl), 6.55 (dd, JHH= 6.6 Hz, 15.9 Hz,

1H, CHallyl), 2.23 (s, 3H, CH3).

OAc(rac)-2-cyclohexenyl acetate[306]

C8H12O2, 140.18 g/mol

2-Cyclohexenol (0.98 ml, 0.98 g, 10 mmol, 1 equiv) was dissolved in THF (25 ml)

together with acetic anhydride (1.1 ml, 1.2 g, 12 mmol, 1.2 equiv), triethylamine

(2.5 ml, 1.8 g, 18 mmol, 1.8 equiv) and 4-dimethylaminopyridine (6.1 mg, 0.05 mmol,

0.005 equiv) at 0 ◦C and the resulting reaction mixture stirred for 1 h before removing the

cooling bath. After stirring over night at rt the solvent was evaporated and the crude product

redissolved in diethyl ether, washed with saturated aqueous NH4Cl and dried over MgSO4.

Flash column chromatography (4:1 hexane/ethyl acetate) over silica gel yielded the pure

product as a colourless oil.

Yield: 584 mg, 42 %. 1H-NMR (300 MHz, CDCl3): δ 5.90 (dt, JHH= 6.3, 3.9 Hz, 1H, CH),

5.66 (d, JHH= Hz, 1H, CH), 5.22 (s, 1H, CH), 2.01 (s, 3H, CH3), 1.5 – 2.1 (m, 6H, CH2).

CAS-number: 14447-34-8

Miyaura-Hayashi reaction[215]

Cyclohexenone (0.036 ml, 0.38 mmol, 1 equiv) was dissolved in ethyl acetate (3 ml) in a

10 ml Schlenk tube. The solution was thoroughly degassed before the addition of rhodium

catalyst 48, phenylboronic acid and 0.075 ml of a degassed aqueous solution of potassium

115

7 Experimental

hydroxide (2.5 M, 0.19 mmol, 0.5 equiv). After the predefined reaction time (cf. Table 19),

the reaction mixture was filtered through celite and the celite washed with several portions of

ethyl acetate. The filtrate was concentrated in vacuo and purified by flash column chromatog-

raphy over silica (n-hexane/ethyl acetate, 7:3) to yield the desired product. Enantiomeric

excess (%ee) was determined by HPLC (OD-H, n-hexane/iPrOH, 99:1, 0.5 ml/min, 254 nm,

tR1=33.7 min (R), tR2

=37.2 min (S)).

O BOHHO

cat.EtOAc

O

Rha, PhB(OH)2, T, t, yield ee

mol% equiv ◦C h % %

4 4 40 24 99.5 rac

4 4 40 1 40 rac

4 1.5 40 24 95 rac

2 4 40 1 60 rac

4 4 0 24 0 n.a.

4 4 rt 24 14 16

4 4 rt 4 11 15aunder the assumption that the rhodium complex

of ligand 5 has a molecular formula of the type

[C40H35ClFe2O2PRhS2]n

Table 19: Rhodium catalysed Miyaura-Hayashi reaction.[215]

Allylic substitution[307]

A 10 ml Schlenk tube was charged with bis((1,3-diphenylallyl)bromopalladium(II)), sulfox-

ophosphine ligand 5 and acetonitrile (1 ml). The solution was stirred at rt for 1 h resulting in

a colour change from orange to brown. 1 mg of salt was added and the solution was brought

to the reaction temperature (cf. Table 20) before the addition of 1,3-diphenylallyl acetate

(126 mg, 0.115 ml, 0.50 mmol, 1 equiv), dimethyl malonate (198 mg, 0.172 ml, 1.5 mmol,

3 equiv) and N,O-bis(trimethylsilyl) acetamide (305 mg, 0.368 ml, 1.5 mmol, 3 equiv) and

116

7.2 Syntheses

stirring for the given reaction time (cf. Table 20). Then the solution was diluted with

diethyl ether, washed with saturated aqueous NH4Cl, NaHCO3 and brine. The organic layer

was dried over MgSO4 concentrated in vacuo and purified by flas column chromatography

over silica (n-hexane/ethyl acetate, 85:15) to yield the desired product. Enantiomeric

excess (%ee) was determined by HPLC (AD-H, n-hexane/iPrOH, 95:5, 0.5 ml/min, 254 nm,

tR1=14.6 min (S), tR2

=19.8 min (R)).

Ph Ph

OAc O

MeO

O

OMe

Pd cat.

N,O–bis(trimethylsilyl)acetamide Ph Ph

O

OMe

O

MeO

Pd, additive T, t, solvent yielda ee

mol% ◦C h % %

5 LiOAc rt 16 AcN 97 77

5 NaOAc rt 16 AcN 99 77

5 KOAc rt 16 AcN 93 78

5 LiOAc rt 16 DCM 95 78

5 LiOAc rt 16 tol 95 74

5 LiOAc rt 16 ether 99 73

10 LiOAc 0 24 AcN 78 74

10 NaOAc 0 24 AcN 76 76adetermined by 1H-NMR, using 1,3,5-Tri-t-

butylbenzene as internal standard.

Table 20: Allylic substitution reaction using the dichloropalladium(II) complex of 5.

117

7 Experimental

118

References

[1] Kealy, T. J.; Pauson, P. L. Nature 1951, 168, 1039 – 1040.

[2] Miller, S. A.; Tebboth, J. A.; Tremaine, J. F. J. Chem. Soc. 1952, 632–635.

[3] Togni, A.; Hayashi, T. Ferrocenes: Homogeneous Catalysis, Organic Synthesis, Materials

Science. Wiley-VCH Verlag GmbH, Weinheim, Germany, 2007.

[4] Štepnicka, P. Ferrocenes: Ligands, Materials and Biomolecules. John Wiley & Sons, Ltd,

Chichester, UK, 2008.

[5] Day, L.-X.; Hou, X.-L. Chiral Ferrocenes in Asymmetric Catalysis. Wiley-VCH Verlag

GmbH & Co. KGaA, Weinheim, Germany, 2010.

[6] Woodward, R. B.; Rosenblum, M.; Whiting, M. C. Journal of the American Chemical

Society 1952, 74, 3458–3459.

[7] Wilkinson, G.; Rosenblum, M.; Whiting, M. C.; Woodward, R. B. Journal of the Ameri-

can Chemical Society 1952, 74, 2125–2126.

[8] Dunitz, J. D.; Orgel, L. E. Nature 1953, 171, 121–122.

[9] Dunitz, J. D.; Orgel, L. E.; Rich, A. Acta Crystallographica 1956, 9, 373–375.

[10] Blaser, H.-U.; Brieden, W.; Pugin, B.; Spindler, F.; Studer, M.; Togni, A. Topics in Catal-

ysis 2002, 19, 3–16.

[11] Zhou, Q.-L. Privileged Chiral Ligands and Catalysts. Wiley-VCH Verlag GmbH & Co.

KGaA, Weinheim, Germany, 2011.

[12] Lednicer, D.; Hauser, C. R. The Journal of Organic Chemistry 1959, 24, 43–46.

[13] Thomson, J. Tetrahedron Letters 1959, 1, 26 – 27.

[14] Schlögel, K. in Topics in Stereochemistry, (John Wiley & Sons, Inc., New York). pp

39 – 91. 1967.

119

http://dx.doi.org/10.1038/1681039b0

http://dx.doi.org/10.1039/JR9520000632

http://pubs.acs.org/doi/abs/10.1021/ja01133a543




http://dx.doi.org/10.1038/171121a0

http://dx.doi.org/10.1107/S0365110X56001091

http://dx.doi.org/10.1023/A%3A1013832630565

http://dx.doi.org/10.1023/A%3A1013832630565

http://pubs.acs.org/doi/abs/10.1021/jo01083a014

http://www.sciencedirect.com/science/article/pii/S0040403901994250

References

[15] Cahn, R. S. Journal of Chemical Education 1964, 41, 116.

[16] Cahn, R. S.; Ingold, C.; Prelog, V. Angewandte Chemie International Edition in English

1966, 5, 385 – 415.

[17] Prelog, V.; Helmchen, G. Angewandte Chemie International Edition in English 1982, 21,

567 – 583.

[18] Deng, W.-P.; Snieckus, V.; Metallinos, C. in Chiral Ferrocenes in Asymmetric Catalysis,

(Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany). pp 15 – 53. 2010.

[19] Whisler, M. C.; MacNeil, S.; Snieckus, V.; Beak, P. Angewandte Chemie International

Edition 2004, 43, 2206 – 2225.

[20] Aratani, T.; Gonda, T.; Nozaki, H. Tetrahedron 1970, 26, 5453 – 5464.

[21] Price, D.; Simpkins, N. S. Tetrahedron Letters 1995, 36, 6135 – 6136.

[22] Tsukazaki, M.; Tinkl, M.; Roglans, A.; Chapell, B. J.; Taylor, N. J.; Snieckus, V. Journal

of the American Chemical Society 1996, 118, 685–686.

[23] Laufer, R. S.; Veith, U.; Taylor, N. J.; Snieckus, V. Organic Letters 2000, 2, 629–631.

[24] Metallinos, C.; Szillat, H.; Taylor, N.; Snieckus, V. Advanced Synthesis Catalysis 2003,

345, 370 – 382.

[25] Dixon, A. J.; McGrath, M. J.; O’Brien, P. Organic Synthesis 2006, 83, 141–154.

[26] Horeau, A. Tetrahedron Letters 1961, 2, 506 – 512.

[27] Horeau, A. Tetrahedron Letters 1962, 3, 965 – 969.

[28] Falk, H.; Schlögl, K. Monatshefte für Chemie und verwandte Teile anderer Wissenschaften

1965, 96, 276–284.

[29] Falk, H.; Schlögl, K. Monatshefte für Chemie und verwandte Teile anderer Wissenschaften

1965, 96, 266–275.

[30] Schlögl, K.; Fried, M.; Falk, H. Monatshefte für Chemie und verwandte Teile anderer

Wissenschaften 1964, 95, 576–597.

[31] Latorre, A.; Urbano, A.; Carmen Carreno, M. Chem. Commun. 2011, 47, 8103–8105.

[32] Blaser, H.-U.; Federsel, H.-J. Asymmetric Catalysis on Industrial Scale. Wiley-VCH

Verlag GmbH & Co. KGaA, Weinheim, Germany, 2010.

120

http://pubs.acs.org/doi/abs/10.1021/ed041p116

http://dx.doi.org/10.1002/anie.196603851







http://www.sciencedirect.com/science/article/pii/004040399501161A

http://pubs.acs.org/doi/abs/10.1021/ja953246q


http://pubs.acs.org/doi/abs/10.1021/ol991381s

http://dx.doi.org/10.1002/adsc.200390042




http://dx.doi.org/10.1007/BF00912319

http://dx.doi.org/10.1007/BF00912319

http://dx.doi.org/10.1007/BF00912318

http://dx.doi.org/10.1007/BF00912318

http://dx.doi.org/10.1007/BF00901324

http://dx.doi.org/10.1007/BF00901324

http://dx.doi.org/10.1039/C1CC12921J

References

[33] Lambusta, D.; Nicolosi, G.; Patti, A.; Piattelli, M. Tetrahedron Letters 1996, 37, 127 –

130.

[34] Bueno, A.; Rosol, M.; García, J.; Moyano, A. Advanced Synthesis Catalysis 2006, 348,

2590 – 2596.

[35] Ogasawara, M.; Watanabe, S.; Nakajima, K.; Takahashi, T. Pure and Applied Chemistry

2008, 80, 1109 – 1113.

[36] Ogasawara, M.; Watanabe, S.; Nakajima, K.; Takahashi, T. Organometallics 2008, 27,

6565–6569.

[37] Ogasawara, M.; Watanabe, S.; Nakajima, K.; Takahashi, T. Journal of the American

Chemical Society 2010, 132, 2136–2137.

[38] Ogasawara, M.; Watanabe, S.; Fan, L.; Nakajima, K.; Takahashi, T. Organometallics

2006, 25, 5201–5203.

[39] Hauser, C. R.; Lindsay, J. K. The Journal of Organic Chemistry 1957, 22, 906–908.

[40] Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi, I. Journal of the American


[41] Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi, I. Angewandte Chemie

1970, 82, 360 – 361.

[42] Stüber, S.; Ugi, I. Synthesis 1973, 309–309.

[43] Boaz, N. W. Tetrahedron Letters 1989, 30, 2061 – 2064.

[44] Wright, J.; Frambes, L.; Reeves, P. Journal of Organometallic Chemistry 1994, 476,

215 – 217.

[45] Schwink, L.; Knochel, P. Tetrahedron Letters 1996, 37, 25 – 28.

[46] Blaser, H.; Spindler, F.; Studer, M. Applied Catalysis A: General 2001, 221, 119 – 143.

[47] Lam, W.-S.; Kok, S.; Au-Yeung, T.-L.; Wu, J.; Cheung, H.-Y.; Lam, F.-L.; Yeung, C.-H.;

Chan, A. Advanced Synthesis Catalysis 2006, 348, 370 – 374.

[48] Blaser, H.-U.; Pugin, B.; Spindler, F.; Thommen, M. Accounts of Chemical Research

2007, 40, 1240–1250.

[49] Gokel, G. W.; Ugi, I. K. Journal of Chemical Education 1972, 49, 294.

121

http://www.sciencedirect.com/science/article/pii/004040399502090X

http://www.sciencedirect.com/science/article/pii/004040399502090X



http://www.iupac.org/publications/pac/80/5/1109/

http://www.iupac.org/publications/pac/80/5/1109/

http://pubs.acs.org/doi/abs/10.1021/om8007663


http://pubs.acs.org/doi/abs/10.1021/ja910348z

http://pubs.acs.org/doi/abs/10.1021/ja910348z






http://dx.doi.org/10.1002/ange.19700820910



http://www.sciencedirect.com/science/article/pii/0022328X94870845


http://www.sciencedirect.com/science/article/pii/0040403995020985

http://www.sciencedirect.com/science/article/pii/S0926860X01008018



http://pubs.acs.org/doi/abs/10.1021/ar7001057


http://dx.doi.org/10.1021/ed049p294

References

[50] Gokel, G.; Hoffmann, P.; Klusacek, H.; Marquarding, D.; Ruch, E.; Ugi, I. Angewandte

Chemie 1970, 82, 77 – 78.

[51] Richards, J. H.; Hill, E. A. Journal of the American Chemical Society 1959, 81, 3484–

3485.

[52] Trifan, D.; Bacskai, R. Tetrahedron Letters 1960, 1, 1 – 8.

[53] Hill, E. A.; Richards, J. H. Journal of the American Chemical Society 1961, 83, 3840–

3846.

[54] Hill, E. A.; Richards, J. H. Journal of the American Chemical Society 1961, 83, 4216–

4221.

[55] Kong, J.-R.; Ngai, M.-Y.; Krische, M. J. Journal of the American Chemical Society 2006,

128, 718–719.

[56] Boaz, N. W.; Jr., J. A. P.; Large, S. E. Tetrahedron Letters 2006, 47, 4033 – 4035.

[57] Boaz, N. W.; Jr., J. A. P.; Large, S. E. Tetrahedron: Asymmetry 2005, 16, 2063 – 2066.

[58] Sturm, T.; Weissensteiner, W.; Spindler, F. Advanced Synthesis Catalysis 2003, 345,

160 – 164.

[59] Schnyder, A.; Hintermann, L.; Togni, A. Angewandte Chemie International Edition in

English 1995, 34, 931 – 933.

[60] Barbaro, P.; Togni, A. Organometallics 1995, 14, 3570–3573.

[61] Hayashi, T.; Yamazaki, A. Journal of Organometallic Chemistry 1991, 413, 295 – 302.

[62] Togni, A.; Breutel, C.; Schnyder, A.; Spindler, F.; Landert, H.; Tijani, A. Journal of the

American Chemical Society 1994, 116, 4062–4066.

[63] Togni, A.; Breutel, C.; Soares, M. C.; Zanetti, N.; Gerfin, T.; Gramlich, V.; Spindler, F.;

Rihs, G. Inorganica Chimica Acta 1994, 222, 213 – 224.

[64] Okoroafor, M. O.; Ward, D. L.; Brubaker, C. H. Organometallics 1988, 7, 1504–1511.

[65] Honeychuck, R. V.; Okoroafor, M. O.; Shen, L. H.; Brubaker, C. H. Organometallics

1986, 5, 482–490.

[66] Hayashi, T.; Mise, T.; Fukushima, M.; Kagotani, M.; Nagashima, N.; Hamada, Y.; Mat-

sumoto, A.; Kawakami, S.; Konishi, M.; Yamamoto, K.; Kumada, M. Bulletin of the

Chemical Society of Japan 1980, 53, 1138–1151.

122










http://pubs.acs.org/doi/abs/10.1021/ja056474l

http://pubs.acs.org/doi/abs/10.1021/ja056474l







http://pubs.acs.org/doi/abs/10.1021/om00007a067

http://www.sciencedirect.com/science/article/pii/0022328X9180058R








References

[67] Sawamura, M.; Hamashima, H.; Ito, Y. Tetrahedron: Asymmetry 1991, 2, 593 – 596.

[68] Sawamura, M.; Hamashima, H.; Sugawara, M.; Kuwano, R.; Ito, Y. Organometallics

1995, 14, 4549–4558.

[69] Rebière, F.; Riant, O.; Ricard, L.; Kagan, H. B. Angewandte Chemie International Edition

in English 1993, 32, 568 – 570.

[70] Zhao, S. H.; Samuel, O.; Kagan, H. B. Organic Syntheses 1990, 68, 49.

[71] Zhao, S.; Samuel, O.; Kagan, H. Tetrahedron 1987, 43, 5135 – 5144.

[72] Klunder, J. M.; Sharpless, K. B. The Journal of Organic Chemistry 1987, 52, 2598–

2602.

[73] Rebière, F.; Samuel, O.; Ricard, L.; Kagan, H. B. The Journal of Organic Chemistry

1991, 56, 5991–5999.

[74] Guillaneux, D.; Kagan, H. B. The Journal of Organic Chemistry 1995, 60, 2502–2505.

[75] Riant, O.; Argouarch, G.; Guillaneux, D.; Samuel, O.; Kagan, H. B. The Journal of

Organic Chemistry 1998, 63, 3511–3514.

[76] Cogan, D. A.; Liu, G.; Kim, K.; Backes, B. J.; Ellman, J. A. Journal of the American


[77] Lagneau, N. M.; Chen, Y.; Robben, P. M.; Sin, H.-S.; Takasu, K.; Chen, J.-S.; Robinson,

P. D.; Hua, D. H. Tetrahedron 1998, 54, 7301 – 7334.

[78] Priego, J.; Mancheno, O. G.; Cabrera, S.; Carretero, J. C. Chem. Commun. 2001, 2026–

2027.

[79] Priego, J.; Mancheño, O. G.; Cabrera, S.; Carretero, J. C. The Journal of Organic

Chemistry 2002, 67, 1346–1353.

[80] Kloetzing, R. J.; Knochel, P. Tetrahedron: Asymmetry 2006, 17, 116 – 123.

[81] Ferber, B.; Kagan, H. Advanced Synthesis Catalysis 2007, 349, 493 – 507.

[82] Riant, O.; Samuel, O.; Kagan, H. B. Journal of the American Chemical Society 1993,

115, 5835–5836.

[83] Hanessian, S.; Ugolini, A.; Dubé, D.; Glamyan, A. Canadian Journal of Chemistry

1984, 62, 2146–2147.

123












http://pubs.acs.org/doi/abs/10.1021/jo9800614

http://pubs.acs.org/doi/abs/10.1021/jo9800614

http://pubs.acs.org/doi/abs/10.1021/ja9809206




http://dx.doi.org/10.1039/B105962A


http://pubs.acs.org/doi/abs/10.1021/jo016271p






http://www.nrcresearchpress.com/doi/abs/10.1139/v84-367


References

[84] Riant, O.; Samuel, O.; Flessner, T.; Taudien, S.; Kagan, H. B. The Journal of Organic

Chemistry 1997, 62, 6733–6745.

[85] Abiko, A.; Masamune, S. Tetrahedron Letters 1992, 33, 5517 – 5518.

[86] McKennon, M. J.; Meyers, A. I.; Drauz, K.; Schwarm, M. The Journal of Organic

Chemistry 1993, 58, 3568–3571.

[87] Broggini, D. F. D. Phosphine and carbene ligands for asymmetric catalysis containing

two planar-chiral ferrocenyl units. Diss. ETH No. 15041, 2003.

[88] Bertogg, A.; Camponovo, F.; Togni, A. European Journal of Inorganic Chemistry 2005,

347 – 356.

[89] Bertogg, A.; Togni, A. Organometallics 2006, 25, 622–630.

[90] Larsen, A. O.; Taylor, R. A.; White, P. S.; Gagné, M. R. Organometallics 1999, 18,

5157–5162.

[91] Richards, C. J.; Damalidis, T.; Hibbs, D. E.; Hursthouse, M. B. Synlett 1995, 16, 74–76.

[92] Richards, C. J.; Mulvaney, A. W. Tetrahedron: Asymmetry 1996, 7, 1419 – 1430.

[93] Sammakia, T.; Latham, H. A.; Schaad, D. R. The Journal of Organic Chemistry 1995,

60, 10–11.

[94] Sammakia, T.; Latham, H. A. The Journal of Organic Chemistry 1995, 60, 6002–6003.

[95] Nishibayashi, Y.; Segawa, K.; Ohe, K.; Uemura, S. Organometallics 1995, 14, 5486–

5487.

[96] Helmchen, G.; Pfaltz, A. Accounts of Chemical Research 2000, 33, 336–345.

[97] Hargaden, G. C.; Guiry, P. J. Chemical Reviews 2009, 109, 2505–2550.

[98] Stuckwisch, C. G. The Journal of Organic Chemistry 1976, 41, 1173–1176.

[99] Dashan, L.; Trippett, S. Tetrahedron Letters 1983, 24, 2039 – 2040.

[100] Schaub, B.; Jenny, T.; Schlosser, M. Tetrahedron Letters 1984, 25, 4097 – 4100.

[101] Takemura, H.; Hirakawa, T.; Shinmyozu, T.; Inazu, T. Tetrahedron Letters 1984, 25,

5053 – 5056.

124

http://pubs.acs.org/doi/abs/10.1021/jo970075u





http://dx.doi.org/10.3929/ethz-a-004614027


http://dx.doi.org/10.1002/ejic.200400691


http://pubs.acs.org/doi/abs/10.1021/om050845p










http://pubs.acs.org/doi/abs/10.1021/cr800400z






References

[102] Craig, D.; Roberts, N.; Tanswell, J. Australian Journal of Chemistry 1990, 43, 1487 –

1496.

[103] Gray, M.; Chapell, B. J.; Felding, J.; Taylor, N. J.; Snieckus, V. Synlett 1998, 19, 422–

424.

[104] Nettekoven, U. A. Phosphorus-Chiral ligands Based on Ferrocene: Stereoselective Syn-

thesis and Application in Asymmeteric Catalysis. Diss. University of Amsterdam, 2000.

[105] Nettekoven, U.; Widhalm, M.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Mereiter, K.;

Lutz, M.; Spek, A. L. Organometallics 2000, 19, 2299–2309.

[106] Nettekoven, U.; Widhalm, M.; Kalchhauser, H.; Kamer, P. C. J.; van Leeuwen, P. W.

N. M.; Lutz, M.; Spek, A. L. The Journal of Organic Chemistry 2001, 66, 759–770.

[107] Vinci, D.; Mateus, N.; Wu, X.; Hancock, F.; Steiner, A.; Xiao, J. Organic Letters 2006,

8, 215–218.

[108] Vinci, D.; Martins, N.; Saidi, O.; Bacsa, J.; Brigas, A.; Xiao, J. Canadian Journal of

Chemistry 2009, 87, 171–175.

[109] Martins, N.; Mateus, N.; Vinci, D.; Saidi, O.; Brigas, A.; Bacsa, J.; Xiao, J. Org. Biomol.

Chem. 2012, 10, 4036–4042.

[110] Pfaltz, A.; Lotz, M.; Schönleber, M.; Pugin, B.; Kesselgruber, M.; Thommen, M. Method

For Producing Orthometalated and Orthosubstituted Aromatic Compounds. patent,

WO2005056566 2005.

[111] Fadini, L. Asymmetric olefin hydroamination catalyzed by Ni(II)-complexes. Diss. ETH

No. 15593, 2004.

[112] Barbaro, P.; Bianchini, C.; Togni, A. Organometallics 1997, 16, 3004–3014.

[113] Barbaro, P.; Bianchini, C.; Oberhauser, W.; Togni, A. Journal of Molecular Catalysis A:

Chemical 1999, 145, 139 – 146.

[114] Hintermann, L.; Perseghini, M.; Barbaro, P.; Togni, A. European Journal of Inorganic

Chemistry 2003, 601 – 609.

[115] Mejía, E.; Togni, A. Organometallics 2011, 30, 4765–4770.

[116] Fadini, L.; Togni, A. Helvetica Chimica Acta 2007, 90, 411 – 424.

125

http://www.publish.csiro.au/paper/CH9901487


http://pubs.acs.org/doi/abs/10.1021/om991013s

http://pubs.acs.org/doi/abs/10.1021/om991013s



http://pubs.acs.org/doi/abs/10.1021/ol0523704

http://pubs.acs.org/doi/abs/10.1021/ol0523704



http://dx.doi.org/10.1039/C2OB25187F

http://dx.doi.org/10.1039/C2OB25187F



http://pubs.acs.org/doi/abs/10.1021/om970116c





http://pubs.acs.org/doi/abs/10.1021/om200621y

http://dx.doi.org/10.1002/hlca.200790048

References

[117] Sadow, A. D.; Haller, I.; Fadini, L.; Togni, A. Journal of the American Chemical Society

2004, 126, 14704–14705.

[118] Sadow, A. D.; Togni, A. Journal of the American Chemical Society 2005, 127, 17012–

17024.

[119] Walz, I. Katalytische enantioselektive Nazarov-Cyclisierung. Diss. ETH No. 17370,

2007.

[120] Walz, I.; Togni, A. Chem. Commun. 2008, 4315–4317.

[121] Öfele, K.; Herrmann, W. A.; Mihalios, D.; Elison, M.; Herdtweck, E.; Scherer, W.; Mink,

J. Journal of Organometallic Chemistry 1993, 459, 177 – 184.

[122] Jafarpour, L.; Nolan, S. P. volume 46 of Advances in Organometallic Chemistry, pp

181 – 222. Academic Press, 2000.

[123] Gischig, S.; Togni, A. European Journal of Inorganic Chemistry 2005, 4745 – 4754.

[124] Piper, T.; Lemal, D.; Wilkinson, G. Naturwissenschaften 1956, 43, 129–129.

[125] Armitage, D. A. F.; Corriu, R. J. P.; Kendrick, T. C.; Parbhoo, B.; Tilley, T. D.; White,

J. W.; Young, J. C. in The Silicon–Heteroatom Bond (1991), (John Wiley & Sons, Inc.,

Chichester, UK). pp 245 – 308. 2010.

[126] Speier, J. L.; Webster, J. A.; Barnes, G. H. Journal of the American Chemical Society

1957, 79, 974–979.

[127] Chalk, A. J.; Harrod, J. F. Journal of the American Chemical Society 1965, 87, 16–21.

[128] Kapoor, P.; Lövqvist, K.; Oskarsson, Å. Acta Crystallographica Section C 1995, 51, 611 –

613.

[129] Chatt, J.; Eaborn, C.; Ibekwe, S. D.; Kapoor, P. N. J. Chem. Soc. A 1970, 1343–1351.

[130] Zhu, J.; Lin, Z.; Marder, T. B. Inorganic Chemistry 2005, 44, 9384–9390.

[131] Kruck, T.; Job, E.; Klose, U. Angewandte Chemie International Edition in English 1968,

7, 374 – 374.

[132] MacInnis, M. C.; MacLean, D. F.; Lundgren, R. J.; McDonald, R.; Turculet, L.

Organometallics 2007, 26, 6522–6525.

[133] Auburn, M. J.; Stobart, S. R. Inorganic Chemistry 1985, 24, 318–323.

126







http://dx.doi.org/10.1039/B806870D

http://www.sciencedirect.com/science/article/pii/0022328X9386070X

http://www.sciencedirect.com/science/article/pii/0022328X9386070X


http://dx.doi.org/10.1007/BF00621565




http://dx.doi.org/10.1107/S0108270194011170

http://dx.doi.org/10.1107/S0108270194011170

http://dx.doi.org/10.1039/J19700001343

http://pubs.acs.org/doi/abs/10.1021/ic0513641





http://pubs.acs.org/doi/abs/10.1021/ic00197a016

References

[134] Joslin, F. L.; Stobart, S. R. J. Chem. Soc., Chem. Commun. 1989, 504–505.

[135] Gossage, R. A.; McLennan, G. D.; Stobart, S. R. Inorganic Chemistry 1996, 35, 1729–

1732.

[136] Brost, R. D.; Bruce, G. C.; Joslin, F. L.; Stobart, S. R. Organometallics 1997, 16, 5669–

5680.

[137] Zhou, X. J.; Stobart, S. R. Organometallics 2001, 20, 1898–1900.

[138] Mitton, S. J.; McDonald, R.; Turculet, L. Organometallics 2009, 28, 5122–5136.

[139] Mitton, S.; McDonald, R.; Turculet, L. Angewandte Chemie International Edition 2009,

48, 8568 – 8571.

[140] MacInnis, M. C.; McDonald, R.; Ferguson, M. J.; Tobisch, S.; Turculet, L. Journal of the


[141] Balakrishna, M. S.; Chandrasekaran, P.; George, P. Coordination Chemistry Reviews

2003, 241, 87 – 117.

[142] Sangtrirutnugul, P.; Stradiotto, M.; Tilley, T. D. Organometallics 2006, 25, 1607–1617.

[143] Sangtrirutnugul, P.; Tilley, T. D. Organometallics 2007, 26, 5557–5568.

[144] Stradiotto, M.; Fujdala, K. L.; Tilley, T. D. Chem. Commun. 2001, 1200–1201.

[145] Davis, D. D.; Gray, C. E. Organometal. Chem. Rev. A 1960, 6, 283.

[146] Gilman, H.; Aoki, D. Journal of Organometallic Chemistry 1964, 1, 449 – 463.

[147] Gilman, H.; Lichtenwalter, G. D. Journal of the American Chemical Society 1958, 80,

608–611.

[148] Gilman, H.; Aoki, D. Journal of Organometallic Chemistry 1964, 2, 89 – 92.

[149] Corriu, R. J. P.; Guérin, C.; Kolani, B. Bulletin de la Société Chimique de France 1985,

973.

[150] Uhlig, W. Progress in Polymer Science 2002, 27, 255 – 305.

[151] Walter, C.; Fröhlich, R.; Oestreich, M. Tetrahedron 2009, 65, 5513 – 5520.

[152] Kleeberg, C.; Feldmann, E.; Hartmann, E.; Vyas, D. J.; Oestreich, M. Chemistry – A

European Journal 2011, 17, 13538 – 13543.

127

http://dx.doi.org/10.1039/C39890000504

http://pubs.acs.org/doi/abs/10.1021/ic941230f

http://pubs.acs.org/doi/abs/10.1021/ic941230f

http://pubs.acs.org/doi/abs/10.1021/om970518k

http://pubs.acs.org/doi/abs/10.1021/om970518k





http://pubs.acs.org/doi/abs/10.1021/ja204935x

http://pubs.acs.org/doi/abs/10.1021/ja204935x



http://pubs.acs.org/doi/abs/10.1021/om050859v

http://pubs.acs.org/doi/abs/10.1021/om700494q








http://dx.doi.org/10.1002/chem.201102367


References

[153] Ojima, I.; Nihonyanagi, M.; Nagai, Y. J. Chem. Soc., Chem. Commun. 1972, 938a–

938a.

[154] Marciniec, B. Hydrosilylation: A Comprehensive Review on Recent Advances, volume 1.

Springer, Netherlands, 2009.

[155] Pioda, G.; Togni, A. Tetrahedron: Asymmetry 1998, 9, 3903 – 3910.

[156] Renner, H.; Schlamp, G.; Kleinwächter, I.; Drost, E.; Lüschow, H. M.; Tews, P.; Panster,

P.; Diehl, M.; Lang, J.; Kreuzer, T.; Knödler, A.; Starz, K. A.; Dermann, K.; Rothaut, J.;

Drieselman, R. (Wiley-VCH Verlag GmbH & Co. KGaA, ). pp 368–369. 2001.

[157] Camponovo, F. Chiral Ferrocenyl Amidines as Modular Ligands for Applications in

Asymmetric Catalysis. Diss. ETH No. 18199, 2009.

[158] Gmelin, Handbuch der Anorganischen Chemie Fe: Org. Verb., volume A5. Springer, 1981.

[159] Etievant, P.; Tainturier, G.; Gautheron, B. Comptes Rendus des Séances de l’Académie des

Sciences, Série C 1976, 283, 233–236.

[160] Gröbel, B.-T.; Seebach, D. Synthesis 1977, 357–402.

[161] Colvin, E. W. Silicon in Organic Synthesis. Butterworth and Co. Publications Ltd,

London, Boston, Sydney, Wellington, Durban, Toronto, 1981.

[162] Reuter, M. J.; Damrauer, R. Journal of Organometallic Chemistry 1974, 82, 201 – 208.

[163] Kondo, T.; Yamamoto, K.; Kumada, M. Journal of Organometallic Chemistry 1972, 35,

C30 – C32.

[164] Kondo, T.; Yamamoto, K.; Omura, T.; Kumada, M. Journal of Organometallic Chemistry

1973, 60, 287 – 301.

[165] Ireland, T.; Almena Perea, J. J.; Knochel, P. Angewandte Chemie International Edition

1999, 38, 1457 – 1460.

[166] Moran, M.; Casado, C. M.; Cuadrado, I.; Losada, J. Organometallics 1993, 12, 4327–

4333.

[167] Losada, J.; Cuadrado, I.; Morán, M.; Casado, C. M.; Alonso, B.; Barranco, M. Analytica

Chimica Acta 1997, 338, 191 – 198.

128

http://dx.doi.org/10.1039/C3972000938A

http://dx.doi.org/10.1039/C3972000938A









http://dx.doi.org/10.1002/(SICI)1521-3773(19990517)38:10<1457::AID-ANIE1457>3.0.CO;2-W

http://dx.doi.org/10.1002/(SICI)1521-3773(19990517)38:10<1457::AID-ANIE1457>3.0.CO;2-W



http://www.sciencedirect.com/science/article/pii/S000326709600462X


References

[168] Cuadrado, I.; Morán, M.; Losada, J.; Casado, C. M.; Pascual, C.; Alonso, B.; Lobete, F.

(JAI Press Inc., Greebwich, Conneticut and London, England). volume 3 of Advances

in Organometallic Chemistry. chapter Organometallic Dendritic Macromolecules, pp

151 – 195. 1996.

[169] Ryan, J.; Speier, J. The Journal of Organic Chemistry 1959, 24, 2052–2053.

[170] Petrow Zhurnal Obshchei Khimii: Journal of General Chemistry of the U.S.S.R. : English

Translation 1960, 30, 376.

[171] Etievant, P.; Gautheron, B.; Tainturier, G. Bulletin de la Société Chimique de France

1978, 292–298.

[172] Hartinger, C. G.; Nazarov, A. A.; Chevchenko, V.; Arion, V. B.; Galanski, M.; Keppler,

B. K. Dalton Trans. 2003, 3098–3102.

[173] Connell, A.; Holliman, P. J.; Butler, I. R.; Male, L.; Coles, S. J.; Horton, P. N.; Hursthouse,

M. B.; Clegg, W.; Russo, L. Journal of Organometallic Chemistry 2009, 694, 2020 –

2028.

[174] Bondi, A. The Journal of Physical Chemistry 1964, 68, 441–451.

[175] Mantina, M.; Chamberlin, A. C.; Valero, R.; Cramer, C. J.; Truhlar, D. G. The Journal

of Physical Chemistry A 2009, 113, 5806–5812.

[176] Wuts, P. G. M.; Greene, T. W. (John Wiley & Sons, Inc., ). pp 431 – 532. 2006.

[177] Soderquist, J. A.; Miranda, E. I. Journal of the American Chemical Society 1992, 114,

10078–10079.

[178] Takaya, J.; Iwasawa, N. Dalton Trans. 2011, 40, 8814–8821.

[179] Appleton, T.; Clark, H.; Manzer, L. Coordination Chemistry Reviews 1973, 10, 335 –

422.

[180] Chan, D.; Duckett, S. B.; Heath, S. L.; Khazal, I. G.; Perutz, R. N.; Sabo-Etienne, S.;

Timmins, P. L. Organometallics 2004, 23, 5744–5756.

[181] Moulton, C. J.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1976, 1020–1024.

[182] Errington, J.; McDonald, W. S.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1980, 2312–

2314.

129


http://dx.doi.org/10.1039/B304115H

http://dx.doi.org/10.1039/B304115H




http://pubs.acs.org/doi/abs/10.1021/j100785a001

http://pubs.acs.org/doi/abs/10.1021/jp8111556

http://pubs.acs.org/doi/abs/10.1021/jp8111556



http://dx.doi.org/10.1039/C1DT10526D



http://pubs.acs.org/doi/abs/10.1021/om049549n

http://pubs.acs.org/doi/abs/10.1021/om049549n

http://dx.doi.org/10.1039/DT9760001020

http://dx.doi.org/10.1039/DT9800002312

http://dx.doi.org/10.1039/DT9800002312

References

[183] van Koten, G.; Timmer, K.; Noltes, J. G.; Spek, A. L. J. Chem. Soc., Chem. Commun.

1978, 250–252.

[184] van Koten, G.; Jastrzebski, J. T.; Noltes, J. G.; Spek, A. L.; Schoone, J. C. Journal of

Organometallic Chemistry 1978, 148, 233 – 245.

[185] Koten, G. Organometallic Pincer Chemistry, volume 40 of Topics in Organometallic

Chemistry. Springer Berlin Heidelberg, 2013.

[186] Morales-Morales, D. Rev. Soc. Quím. Méx. 2004, 48, 338–346.

[187] Albrecht, M.; van Koten, G. Angewandte Chemie International Edition 2001, 40, 3750 –

3781.

[188] van der Boom, M. E.; Milstein, D. Chemical Reviews 2003, 103, 1759–1792.

[189] Dupont, J.; Consorti, C. S.; Spencer, J. The Chemistry of Pincer Compounds. Elsevier

Science B.V., Amsterdam, 2007.

[190] Leis, W.; Mayer, H. A.; Kaska, W. C. Coordination Chemistry Reviews 2008, 252, 1787 –

1797.

[191] Shaw, B. L. Journal of the American Chemical Society 1975, 97, 3856–3857.

[192] Shaw, B. L. Journal of Organometallic Chemistry 1980, 200, 307 – 318.

[193] Haenel, M. W.; Oevers, S.; Angermund, K.; Kaska, W. C.; Fan, H.-J.; Hall, M. B. Ange-

wandte Chemie International Edition 2001, 40, 3596 – 3600.

[194] M. Jensen, C. Chem. Commun. 1999, 2443–2449.

[195] Singleton, J. T. Tetrahedron 2003, 59, 1837 – 1857.

[196] Zhao, J.; Goldman, A. S.; Hartwig, J. F. Science 2005, 307, 1080–1082.

[197] Goldman, A. S.; Roy, A. H.; Huang, Z.; Ahuja, R.; Schinski, W.; Brookhart, M. Science

2006, 312, 257–261.

[198] Pugh, D.; Danopoulos, A. A. Coordination Chemistry Reviews 2007, 251, 610 – 641.

[199] Corey, J. Y.; Braddock-Wilking, J. Chemical Reviews 1999, 99, 175–292.

[200] Auburn, M. J.; Holmes-Smith, R. D.; Stobart, S. R.; Bakshi, P. K.; Cameron, T. S.


130

http://dx.doi.org/10.1039/C39780000250

http://dx.doi.org/10.1039/C39780000250

http://www.sciencedirect.com/science/article/pii/S0022328X0090980X

http://www.sciencedirect.com/science/article/pii/S0022328X0090980X

http://dx.doi.org/10.1002/1521-3773(20011015)40:20<3750::AID-ANIE3750>3.0.CO;2-6

http://dx.doi.org/10.1002/1521-3773(20011015)40:20<3750::AID-ANIE3750>3.0.CO;2-6

http://pubs.acs.org/doi/abs/10.1021/cr960118r





http://dx.doi.org/10.1002/1521-3773(20011001)40:19<3596::AID-ANIE3596>3.0.CO;2-C

http://dx.doi.org/10.1002/1521-3773(20011001)40:19<3596::AID-ANIE3596>3.0.CO;2-C

http://dx.doi.org/10.1039/A903573G


http://www.sciencemag.org/content/307/5712/1080.abstract




http://pubs.acs.org/doi/abs/10.1021/cr9701086



References

[201] Ruddy, A. J.; Mitton, S. J.; McDonald, R.; Turculet, L. Chem. Commun. 2012, 48,

1159–1161.

[202] MacLean, D. F.; McDonald, R.; Ferguson, M. J.; Caddell, A. J.; Turculet, L. Chem.

Commun. 2008, 5146–5148.

[203] Butler, I. R. Inorganic Chemistry Communications 2008, 11, 15 – 19.

[204] Rebière, F.; Samuel, O.; Kagan, H. Tetrahedron Letters 1990, 31, 3121 – 3124.

[205] Baechler, R. D.; Mislow, K. Journal of the American Chemical Society 1970, 92, 3090–

3093.

[206] Rauk, A.; Allen, L. C.; Mislow, K. Angewandte Chemie International Edition in English

1970, 9, 400 – 414.

[207] Heinemann, F.; Weber, I.; Zenneck, U. Journal of Chemical Crystallography 2007, 37,

165–170.

[208] Sinnokrot, M. O.; Valeev, E. F.; Sherrill, C. D. Journal of the American Chemical Society

2002, 124, 10887–10893.

[209] Blount, J.; Camp, D.; Hart, R.; Healy, P.; Skelton, B.; White, A. Australian Journal of

Chemistry 1994, 47, 1631 – 1639.

[210] Houlton, A.; Roberts, R. M. G.; Silver, J.; Drew, M. G. B. J. Chem. Soc., Dalton Trans.

1990, 1543–1547.

[211] Romeo, R.; Tobe, M. L. Inorganic Chemistry 1974, 13, 1991–1996.

[212] Kukushkin, Y. N.; Vyaz’menskii, Y. E.; Zorina, L. I. Russian Journal of Inorganic

Chemistry 1968, 13, 1573 – 1576.

[213] Kukushkin, Y. N.; Trusova, K. M. Russian Journal of Inorganic Chemistry 1971, 16,

139–140.

[214] Mercer, A.; Trotter, J. J. Chem. Soc., Dalton Trans. 1975, 2480–2483.

[215] Dornan, P. K.; Leung, P. L.; Dong, V. M. Tetrahedron 2011, 67, 4378 – 4384.

[216] Rayner, D. R.; Gordon, A. J.; Mislow, K. Journal of the American Chemical Society 1968,

90, 4854–4860.

131

http://dx.doi.org/10.1039/C2CC16751D

http://dx.doi.org/10.1039/C2CC16751D

http://dx.doi.org/10.1039/B811811F

http://dx.doi.org/10.1039/B811811F







http://dx.doi.org/10.1007/s10870-006-9177-2

http://dx.doi.org/10.1007/s10870-006-9177-2

http://pubs.acs.org/doi/abs/10.1021/ja025896h

http://pubs.acs.org/doi/abs/10.1021/ja025896h



http://dx.doi.org/10.1039/DT9900001543

http://dx.doi.org/10.1039/DT9900001543


http://dx.doi.org/10.1039/DT9750002480




References

[217] Kingsbury, C. A.; Cram, D. J. Journal of the American Chemical Society 1960, 82, 1810–

1819.

[218] Fernández, I.; Khiar, N. Chemical Reviews 2003, 103, 3651–3706.

[219] Kagan, H. in Organosulfur Chemistry in Asymmetric Synthesis, (Wiley-VCH Verlag

GmbH & Co. KGaA, Weinheim, Germany). pp 1 – 29. 2009.

[220] Solladié, G. Synthesis 1981, 185–196.

[221] Valentine Jr, D.; Scott, J. W. Synthesis 1978, 329–356.

[222] Caplar, V.; Comisso, G.; Šunjic, V. Synthesis 1981, 85–116.

[223] Pellissier, H. Tetrahedron 2006, 62, 5559 – 5601.

[224] James, B. R.; McMillan, R. S.; Reimer, K. J. Journal of Molecular Catalysis 1976, 1,

439 – 441.

[225] Kagan, H. B.; Dang-Tuan-Phat Journal of the American Chemical Society 1972, 94,

6429–6433.

[226] James, B. R.; McMillan, R. S. Canadian Journal of Chemistry 1977, 55, 3927–3932.

[227] Kvintovics, P.; James, B. R.; Heil, B. J. Chem. Soc., Chem. Commun. 1986, 1810–1811.

[228] Alcock, N. W.; Brown, J. M.; Evans, P. L. Journal of Organometallic Chemistry 1988,

356, 233 – 247.

[229] Petra, D. G. I.; Kamer, P. C. J.; Spek, A. L.; Schoemaker, H. E.; van Leeuwen, P. W. N. M.

The Journal of Organic Chemistry 2000, 65, 3010–3017.

[230] Khiar, N.; Fernández, I.; Alcudia, F. Tetrahedron Letters 1993, 34, 123 – 126.

[231] Ichikawa, E.; Suzuki, M.; Yabu, K.; Albert, M.; Kanai, M.; Shibasaki, M. Journal of the


[232] Fernández, I.; Valdivia, V.; Leal, M. P.; Khiar, N. Organic Letters 2007, 9, 2215–2218.

[233] Mariz, R.; Luan, X.; Gatti, M.; Linden, A.; Dorta, R. Journal of the American Chemical

Society 2008, 130, 2172–2173.

[234] Mariz, R.; Burgi, J.; Gatti, M.; Drinkel, E.; Luan, X.; Dorta, R. CHIMIA International

Journal for Chemistry 2009, 63, 508–511.

132



http://pubs.acs.org/doi/abs/10.1021/cr990372u







http://dx.doi.org/10.1039/C39860001810



http://pubs.acs.org/doi/abs/10.1021/jo991700t

http://pubs.acs.org/doi/abs/10.1021/jo991700t


http://pubs.acs.org/doi/abs/10.1021/ja045966f

http://pubs.acs.org/doi/abs/10.1021/ja045966f

http://pubs.acs.org/doi/abs/10.1021/ol070729d



http://www.ingentaconnect.com/content/scs/chimia/2009/00000063/00000007/art00010

http://www.ingentaconnect.com/content/scs/chimia/2009/00000063/00000007/art00010

References

[235] Mariz, R.; Poater, A.; Gatti, M.; Drinkel, E.; Bürgi, J. J.; Luan, X.; Blumentritt, S.;

Linden, A.; Cavallo, L.; Dorta, R. Chemistry – A European Journal 2010, 16, 14335 –

14347.

[236] Bürgi, J.; Mariz, R.; Gatti, M.; Drinkel, E.; Luan, X.; Blumentritt, S.; Linden, A.; Dorta,

R. Angewandte Chemie International Edition 2009, 48, 2768 – 2771.

[237] Chen, Q.-A.; Dong, X.; Chen, M.-W.; Wang, D.-S.; Zhou, Y.-G.; Li, Y.-X. Organic Letters

2010, 12, 1928–1931.

[238] Chen, J.; Chen, J.; Lang, F.; Zhang, X.; Cun, L.; Zhu, J.; Deng, J.; Liao, J. Journal of

the American Chemical Society 2010, 132, 4552–4553.

[239] Zhang, X.; Chen, J.; Han, F.; Cun, L.; Liao, J. European Journal of Organic Chemistry

2011, 1443 – 1446.

[240] Khiar, N.; Salvador, Á.; Valdivia, V.; Chelouan, A.; Alcudia, A.; Álvarez, E.; Fernández,

I. The Journal of Organic Chemistry 2013, 78, 6510–6521.

[241] Drinkel, E. E.; Wu, L.; Linden, A.; Dorta, R. Organometallics 2014, 33, 627–636.

[242] Miyashita, A.; Yasuda, A.; Takaya, H.; Toriumi, K.; Ito, T.; Souchi, T.; Noyori, R. Jour-

nal of the American Chemical Society 1980, 102, 7932 – 7934.

[243] Chen, M. S.; White, M. C. Journal of the American Chemical Society 2004, 126, 1346–

1347.

[244] Chen, M. S.; Prabagaran, N.; Labenz, N. A.; White, M. C. Journal of the American


[245] Fraunhoffer, K. J.; Prabagaran, N.; Sirois, L. E.; White, M. C. Journal of the American


[246] Stang, E. M.; Christina White, M. Nat Chem 2009, 1, 547 – 551.

[247] Nesmejanowa, O. A.; Perewalowa, E. G. Doklady Akademii Nauk SSSR 1959, 126,

1004 – 1006.

[248] Perewalowa, E. G.; Nesmejanowa, O. A. Doklady Akademii Nauk SSSR 1960, 132,

1093 – 1094.

[249] Sawamura, M.; Yamauchi, A.; Takegawa, T.; Ito, Y. J. Chem. Soc., Chem. Commun.

1991, 874–875.

133






http://pubs.acs.org/doi/abs/10.1021/ol100536e

http://pubs.acs.org/doi/abs/10.1021/ol100536e



http://dx.doi.org/10.1002/ejoc.201001613

http://dx.doi.org/10.1002/ejoc.201001613

http://pubs.acs.org/doi/abs/10.1021/jo400700m

http://pubs.acs.org/doi/abs/10.1021/jo400700m




http://pubs.acs.org/doi/abs/10.1021/ja039107n

http://pubs.acs.org/doi/abs/10.1021/ja039107n



http://pubs.acs.org/doi/abs/10.1021/ja063096r

http://pubs.acs.org/doi/abs/10.1021/ja063096r

http://dx.doi.org/10.1038/nchem.351

http://dx.doi.org/10.1039/C39910000874

http://dx.doi.org/10.1039/C39910000874

References

[250] Espino, G.; Xiao, L.; Puchberger, M.; Mereiter, K.; Spindler, F.; Manzano, B. R.; Jalon,

F. A.; Weissensteiner, W. Dalton Trans. 2009, 2751–2763.

[251] Xiao, L.; Mereiter, K.; Spindler, F.; Weissensteiner, W. Tetrahedron: Asymmetry 2001,

12, 1105 – 1108.

[252] Kuwano, R. in Chiral Ferrocenes in Asymmetric Catalysis, (Wiley-VCH Verlag GmbH &

Co. KGaA, Weinheim, Germany). pp 283 – 305. 2010.

[253] Zirakzadeh, A.; Groß, M. A.; Wang, Y.; Mereiter, K.; Spindler, F.; Weissensteiner, W.


[254] Dong, T.-Y.; Chang, C.-K.; Lee, S.-H.; Lai, L.-L.; Chiang, M. Y.-N.; Lin, K.-J.


[255] Dong, T.-Y.; Huang, B.-R.; Lin, M.-C.; Chiang, M. Y. Polyhedron 2003, 22, 1199 – 1204.

[256] Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785–789.

[257] Becke, A. D. Phys. Rev. A 1988, 38, 3098–3100.

[258] Becke, A. D. The Journal of Chemical Physics 1993, 98, 5648–5652.

[259] Perdew, J. P. Phys. Rev. B 1986, 33, 8822–8824.

[260] Gaussian 09, Rev D.01Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;

Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G.

A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.;

Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa,

J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J.

A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.;

Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant,

J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox,

J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R.

E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.;

Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich,

S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J.

Gaussian, Inc., Wallingford CT, 2009.

[261] Gauss, J. The Journal of Chemical Physics 1993, 99, 3629–3643.

[262] London, F. Journal de Physique et le Radium 1937, 8, 397.

134

http://dx.doi.org/10.1039/B816544K

http://dx.doi.org/10.1039/B816544K





http://pubs.acs.org/doi/abs/10.1021/om970746e

http://pubs.acs.org/doi/abs/10.1021/om970746e


http://link.aps.org/doi/10.1103/PhysRevB.37.785

http://link.aps.org/doi/10.1103/PhysRevA.38.3098

http://scitation.aip.org/content/aip/journal/jcp/98/7/10.1063/1.464913

http://link.aps.org/doi/10.1103/PhysRevB.33.8822

http://scitation.aip.org/content/aip/journal/jcp/99/5/10.1063/1.466161

http://jphysrad.journaldephysique.org/index.php?option=com_toc&url=/articles/jphysrad/abs/1937/10/contents/contents.html

References

[263] Ditchfield, R. Molecular Physics 1974, 27, 789–807.

[264] Wolinski, K.; Hinton, J. F.; Pulay, P. Journal of the American Chemical Society 1990,

112, 8251–8260.

[265] Biscarini, P.; Fusina, L.; Nivellini, G. D. J. Chem. Soc., Dalton Trans. 1972, 1921–1923.

[266] Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A. G.; Taylor, R. J. Chem.

Soc., Perkin Trans. 2 1987, S1–S19.

[267] Childs, R. F.; Mulholland, D. L.; Nixon, A. Canadian Journal of Chemistry 1982, 60,

801–808.

[268] Childs, R. F.; Mulholland, D. L.; Nixon, A. Canadian Journal of Chemistry 1982, 60,

809–812.

[269] Brunn, J.; Beck, C. Zeitschrift für Chemie 1977, 17, 296 – 297.

[270] Laszlo, P.; Teston, M. Journal of the American Chemical Society 1990, 112, 8750–8754.

[271] Mallouk, T. E.; Rosenthal, G. L.; Mueller, G.; Brusasco, R.; Bartlett, N. Inorganic

Chemistry 1984, 23, 3167–3173.

[272] Brownridge, S.; Krossing, I.; Passmore, J.; Jenkins, H.; Roobottom, H. Coordination

Chemistry Reviews 2000, 197, 397 – 481.

[273] Christe, K. O.; Dixon, D. A.; McLemore, D.; Wilson, W. W.; Sheehy, J. A.; Boatz, J. A.

Journal of Fluorine Chemistry 2000, 101, 151 – 153.

[274] Hwang, I.-C.; Seppelt, K. Angewandte Chemie 2001, 113, 3803 – 3805.

[275] Cameron, T. S.; Deeth, R. J.; Dionne, I.; Du, H.; Jenkins, H. D. B.; Krossing, I.; Pass-

more, J.; Roobottom, H. K. Inorganic Chemistry 2000, 39, 5614–5631.

[276] Krossing, I.; Bihlmeier, A.; Raabe, I.; Trapp, N. Angewandte Chemie International Edi-

tion 2003, 42, 1531 – 1534.

[277] Butti, P. Catalytic, enantioselective carbon-phosphorus bond forming reactions. Diss.

ETH No. 18839, 2009.

[278] Mita, T.; Chen, J.; Sugawara, M.; Sato, Y. Angewandte Chemie International Edition

2011, 50, 1393–1396.

[279] Mita, T.; Higuchi, Y.; Sato, Y. Organic Letters 2011, 13, 2354–2357.

135

http://www.tandfonline.com/doi/abs/10.1080/00268977400100711



http://dx.doi.org/10.1039/DT9720001921

http://dx.doi.org/10.1039/P298700000S1

http://dx.doi.org/10.1039/P298700000S1





http://dx.doi.org/10.1002/zfch.19770170811








http://dx.doi.org/10.1002/1521-3757(20011001)113:19<3803::AID-ANGE3803>3.0.CO;2-J

http://pubs.acs.org/doi/abs/10.1021/ic990760e

http://pubs.acs.org/doi/abs/10.1021/ic990760e







http://pubs.acs.org/doi/abs/10.1021/ol200599d

References

[280] Mita, T.; Higuchi, Y.; Sato, Y. Synthesis 2012, 43, 194–200.

[281] Mita, T.; Sugawara, M.; Hasegawa, H.; Sato, Y. The Journal of Organic Chemistry 2012,

77, 2159–2168.

[282] Liebeskind, L. S.; na Cabrera, P. Organic Syntheses 2000, 77, 135.

[283] Eisenberger, P.; Gischig, S.; Togni, A. Chemistry – A European Journal 2006, 12, 2579–

2586.

[284] Kieltsch, I.; Eisenberger, P.; Togni, A. Angewandte Chemie 2007, 119, 768–771.

[285] Capone, S.; Kieltsch, I.; Flögel, O.; Lelais, G.; Togni, A.; Seebach, D. Helvetica Chimica

Acta 2008, 91, 2035–2056.

[286] Stanek, K.; Koller, R.; Kieltsch, I.; Eisenberger, P.; Togni, A. 2009. Trifluoromethyl-1,3-

dihydro-3,3-dimethyl-1,2-benziodoxole. e-EROS Encyclopedia of Reagents for Organic

Synthesis.

[287] Stanek, K.; Koller, R.; Kieltsch, I.; Eisenberger, P.; Togni, A. 2009. 1-(Trifluoromethyl)-

1,2-benziodoxol-3(1H)-one. e-EROS Encyclopedia of Reagents for Organic Synthesis.

[288] Eisenberger, P.; Kieltsch, I.; Koller, R.; Stanek, K.; Togni, A. Organic Synthesis 2011,

88, 168 – 180.

[289] Santschi, N.; Togni, A. The Journal of Organic Chemistry 2011, 76, 4189–4193.

[290] Rhode, C.; Lemke, J.; Lieb, M.; Metzler-Nolte, N. Synthesis 2009, 2015–2018.

[291] Teverovskiy, G.; Surry, D. S.; Buchwald, S. L. Angewandte Chemie International Edition

2011, 50, 7312–7314.

[292] Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-Sensitive Compounds. Wiley,

Chichester, 2nd edition, 1986.

[293] Solladié, G.; Hutt, J.; Girardin, A. Synthesis 1987, 173–173.

[294] Solladié, G.; Somny, F.; Colobert, F. Tetrahedron: Asymmetry 1997, 8, 801 – 810.

[295] Aso, Y.; Yamashita, H.; Otsubo, T.; Ogura, F. The Journal of Organic Chemistry 1989,

54, 5627–5629.

[296] Harris, R. K.; Becker, E. D.; Cabral de Menezes, S. M.; Goodfellow, R.; Granger, P. Pure

and Applied Chemistry 2001, 73, 1795–1818.

136



http://www.orgsyn.org/orgsyn/prep.asp?prep=v77p0135






http://dx.doi.org/10.1002/047084289X.rn01120





http://pubs.acs.org/doi/abs/10.1021/jo200522w






http://dx.doi.org/10.1351/pac200173111795

http://dx.doi.org/10.1351/pac200173111795

References

[297] SAINT+, Software for CCD Diffractometers, v. 6.01 and SAINT, v. 6.02. Bruker AXS,

Inc., Madison, WI, 2001.

[298] Sheldrick, G. M. Acta Crystallographica 1990, A46, 467–473.

[299] Sheldrick, G. M.; SHELXL-97 Program for Crystal Structure Refinement. Universität

Göttingen, Göttingen, Germany, 1999.

[300] Blessing, R. H. Acta Crystallographica 1995, A51, 33–38.

[301] Flack, H. D. Acta Crystallographica 1983, A39, 876–881.

[302] Bernadinelli, G.; Flack, H. D. Acta Crystallographica 1985, A41, 500–511.

[303] Acta Crystallographica 2010, C66, e1–e8.

[304] Herberhold, M.; Nuyken, O.; Pöhlmann, T. Journal of Organometallic Chemistry 1991,

405, 217 – 227.

[305] Kauffman, G. B.; Teter, L. A.; C., I. T.; Clifford, A. in Inorganic Syntheses, (John Wiley

& Sons, Inc., Hoboken, NJ, USA). pp 9 – 12. 2007.

[306] Onaran, M. B.; Seto, C. T. The Journal of Organic Chemistry 2003, 68, 8136–8141.

[307] Chen, J.; Lang, F.; Li, D.; Cun, L.; Zhu, J.; Deng, J.; Liao, J. Tetrahedron: Asymmetry

2009, 20, 1953 – 1956.

137

http://dx.doi.org/10.1107/S0108767390000277

http://dx.doi.org/10.1107/S0108767394005726

http://dx.doi.org/10.1107/S0108767383001762

http://dx.doi.org/10.1107/S0108767385001064

http://dx.doi.org/10.1107/S0108270109047817

http://www.sciencedirect.com/science/article/pii/0022328X9186275U

http://www.sciencedirect.com/science/article/pii/0022328X9186275U




References

138

8 Appendix

8.1 Abbreviations

Ac acetyl

aq. aqueous

arom aromatic

Bn benzyl

Bp boiling point

Bu butyl

COD 1,5-cyclooctadiene

dba dibenzylideneacetone

CIP Cahn-Ingold-Prelog system for the assignment of stereoconfiguration

COSY correlation spectroscopy

Cp cyclopentadienyl

d days

decomp decomposition

DMAP 4-dimethylaminopyridine

DMG directing metalation group

DMSO dimethylsulfoxide

dr diastereomeric ratio

EA elemental analysis

ee enantiomeric excess

EI electron ionisation (former: electron impact)

ESI electrospray ionisation

Et ethyl

equiv equivalent

h hour

HMBC heteronuclear multiple-bond correlation spectroscopy

HMQC heteronuclear multiple-quantum correlation spectroscopy

HPLC high performance liquid chromatography

HRMS high resolution mass spectrometry

HSQC heteronuclear single-quantum correlation spectroscopy

Hz Hertz

INEPT insensitive nuclei enhanced by polarisation transfer

i-Pr iso-propyl

xiii

Appendix

IR infrared

J coupling constant

MALDI matrix-assisted laser desorption / ionisation

Me methyl

MeOH methanol

min minute

MS mass spectrometry

NMR nuclear magnetic resonance

NOESY nuclear Overhauser effect spectroscopy

Np naphthyl

ORTEP Oak Ridge thermal ellipsoid plot

OTf trifluoromethanesulfonate (triflate)

Ph phenyl

PPFA (SFc)-1-diphenylphosphino-2-[(R)-(1-N,N-dimethylamino)ethyl]ferrocene

ppm parts per million

rac racemic

rt room temperature

TBAF tetrabutylammonium fluoride

t-Bu tert-butyl

THF tetrahydrofuran

TLC thin layer chromatography

TMEDA tetramethylethylendiamine

Ts tosyl

xiv

Appendix

8.2 Crystallographic Data

(SFc)-2-[α-(Diphenylphosphino)ferrocenyl]-1,3-dithiane (25)

identification code pl047 CCDC number

cryst. method. DCM/n-hexane empirical formula C26H25FePS2

shape plate moiety formula C26H25FePS2

color orange Mr 488.40

cryst size (mm) 0.19 × 0.14 × 0.05 T (K) 100(2)

exp. time/frame (s) 10 solution method direct

crystal system monoclinic space group P21

a (Å) 8.9024(11) α (◦) 90

b (Å) 11.0031(13) β (◦) 109.225(2)

c (Å) 12.1109(14) γ (◦) 90

V (Å3) 1120.2(2) Z 2

ρcalc (g cm−3) 1.448 µ (mm−1) 0.942

θmin, θmax (◦) 2.42, 28.38 F000 508

limiting indices −11≤ h≤ 11 data 5519

−14≤ k ≤ 14 restraints 1

−16≤ l ≤ 15 parameters 271

collected/unique reflexions 11713 / 5519 Rint 0.0373

Tmax, Tmin 0.9570, 0.8435 ∆ρmax, ∆ρmin (e Å−3) 0.632, –0.270

final R [I > 2σ(I)] 0.0400 S 1.010

final R [all data] 0.0447 Flack parameter 0.015(14)

xv

Appendix

(SFc,SFc,SS,SS)-Bis-[2-(p-tolylsulfinyl)ferrocenyl]phenylphosphine (5)

url identification code lm_pl_010 CCDC number

cryst. method. DCM/n-hexane empirical formula C40H35.96Fe2O2.48PS2

shape prism moiety formula C40H35Fe2O2PS2, H0.96O0.48


cryst size (mm) 0.48 × 0.37 × 0.27 T (K) 100(2)


crystal system orthorhombic space group P212121

a (Å) 11.6275(6) α (◦) 90

b (Å) 15.9011(8) β (◦) 90

c (Å) 17.8262(8) γ (◦) 90

V (Å3) 3295.9(3) Z 4

ρcalc (g cm−3) 1.536 µ (mm−1) 1.094

θmin, θmax (◦) 1.72, 28.33 F000 1575





Tmax, Tmin 0.7566, 0.6239 ∆ρmax, ∆ρmin (e Å−3) 0.552, –0.276

final R [I > 2σ(I)] 0.0335 S 1.010


xvi

Appendix

(RFc,RFc,RS,RS)-Bis-[2-(t-butylsulfinyl)ferrocene] (6)

identification code mm-03_d CCDC number

cryst. method. DCM empirical formula C28H34Fe2O2S2

shape needle moiety formula C28H34Fe2O2S2

color yellow Mr 578.37

cryst size (mm) 0.40 × 0.11 × 0.08 T (K) 100(2)



a (Å) 9.8640(6) α (◦) 90

b (Å) 12.9300(8) β (◦) 90

c (Å) 20.0423(13) γ (◦) 90

V (Å3) 2556.2(3) Z 4

ρcalc (g cm−3) 1.503 µ (mm−1) 1.323

θmin, θmax (◦) 1.87, 31.15 F000 1208





Tmax, Tmin ∆ρmax, ∆ρmin (e Å−3) 0.431, –0.545

final R [I > 2σ(I)] 0.0373 S 0.955


xvii

Appendix

(Ra,RFc,RFc)-Bis-[2-(t-butylsulfanyl)ferrocene] (7)

identification code mm13 CCDC number

cryst. method. DCM empirical formula C28H34Fe2S2

shape prism moiety formula C28H34Fe2S2


cryst size (mm) 0.17 × 0.13 × 0.12 T (K) 100(2)



a (Å) 9.9678(5) α (◦) 90

b (Å) 12.6621(6) β (◦) 90

c (Å) 20.1445(10) γ (◦) 90

V (Å3) 2542.5(2) Z 4

ρcalc (g cm−3) 1.427 µ (mm−1) 1.320

θmin, θmax (◦) 1.90, 31.16 F000 1144





Tmax, Tmin ∆ρmax, ∆ρmin (e Å−3) 0.387, –0.425

final R [I > 2σ(I)] 0.0329 S 0.945


xviii

In Copyright - Non-Commercial Use Permitted Rights ......Kamiyama, Raul Pereira, Dr. Raphaël...

Documents

Transcript of In Copyright - Non-Commercial Use Permitted Rights ......Kamiyama, Raul Pereira, Dr. Raphaël...