Probing the Inverse Trans Influence in Americium and ...

doi.org/10.26434/chemrxiv.9992402.v1

Probing the Inverse Trans Influence in Americium and LanthanideTribromide Tris(tricyclohexylphosphine oxide)Cory Windorff, Cristian Celis-Barros, Joseph Sperling, Noah Mckinnon, Thomas Albrecht-Schmitt

Submitted date: 16/10/2019 • Posted date: 21/10/2019Licence: CC BY-NC-ND 4.0Citation information: Windorff, Cory; Celis-Barros, Cristian; Sperling, Joseph; Mckinnon, Noah;Albrecht-Schmitt, Thomas (2019): Probing the Inverse Trans Influence in Americium and LanthanideTribromide Tris(tricyclohexylphosphine oxide). ChemRxiv. Preprint.

The synthesis, characterization, and theoretical analysis of meridional americium tribromidetris(tricyclohexylphosphine oxide), mer-AmBr3(OPcy3)3 has been achieved and is compared with its earlylanthanide (La to Nd) analogs. The data show that homo trans ligands show significantly shorter bonds thanthe cis or hetero trans ligands. This is particularly pronounced in the americium compound. DFT along withmulticonfigurational CASSCF calculations show that the contraction of the bonds relates qualitatively withoverall covalency, i.e. americium shows the most covalent interactions compared to lanthanides. . However,the involvement of the 5p and 6p shells in bonding follows a different order, namely cerium > neodymium ~americium. This study provides further insight into the mechanisms by which ITI operates in low-valent f-blockcomplexes.

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1

Probing the inverse trans influence in americium and lanthanide

tribromide tris(tricyclohexylphosphine oxide)†

Cory J. Windorff, Cristian Celis-Barros, Joseph M. Sperling, Noah C. McKinnon, Thomas E.

Albrecht–Schmitt*

Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, RM. 118 DLC,

Tallahassee, Florida 32306, USA. E-mail: [email protected];

†Electronic supplementary information (ESI) available. Photographs of compounds, NMR spectra, electronic

absorption spectra, additional theoretical calculation and crystallographic details for CCDC #######–#######.

ORCID: Cory J. Windorff: 0000-0002-5208-9129; Cristian Celis-Barros: 0000-0002-4685-5229; Joseph M.

Sperling: 0000-0003-1916-5633; Thomas E. Albrecht-Schmitt: 0000-0002-2989-3311

Abstract

The synthesis, characterization, and theoretical analysis of meridional americium tribromide

tris(tricyclohexylphosphine oxide), mer-AmBr3(OPcy3)3 has been achieved and is compared

with its early lanthanide (La to Nd) analogs. The data show that homo trans ligands show

significantly shorter bonds than the cis or hetero trans ligands. This is particularly

pronounced in the americium compound. DFT along with multiconfigurational CASSCF

calculations show that the contraction of the bonds relates qualitatively with overall

covalency, i.e. americium shows the most covalent interactions compared to lanthanides. .

However, the involvement of the 5p and 6p shells in bonding follows a different order,

namely cerium > neodymium ~ americium. This study provides further insight into the

mechanisms by which ITI operates in low-valent f-block complexes.

mailto:[email protected]

2

Introduction

Phosphine oxides are highly stable ligands that have been utilized primarily for catalysis on

elements across the periodic table.1 The study of phosphine oxides with f-elements has

primarily focused on their use in extraction processes2-5

and in (pseudo)halide/nitrate f-

element starting materials.6-9

The effect of two ligands trans to one another is most

prototypically examined in the actinyls, AnO2n+

, where the trans-oxygens display unusually

short bond distances and high bond strength, best described as bond order of three.10

This

effect, termed the inverse trans influence (ITI) has become the focus of several experimental

and theoretical investigations.11-17

A prototypical examination on the effect of ITI is through

the use or meridional octahedral compounds, e.g. mer-MX3L3 Figure 1, which has been

thoroughly studied in the transition metal series, but is significantly less studied in the f-

block.18

However, the primary focus of structural and theoretical studies on actinide

molecules displaying the ITI effect have been focused on high valent, +4 to +6, oxidation

states.13, 19

Lanthanides have only been subjected to structural studies in the +3 oxidation

state,12, 20

with some analysis of Ce(IV) and hypothetical Pr(IV) and Tb(IV) molecules.15, 17

The amount of ITI can be quantified as a percentage that implies that the lower the

percentage value the larger the ITI effect, Equation 1, where r = bond distance, M = metal, X

= neutral or anionic ligand.21

ITI =r(M − Xtrans)

r(M − Xcis)x100

(1)

3

The minor actinides, Am and Cm, contribute high levels of radiation and heat in spent

nuclear fuel. Long-lived isotopes of Am [241

Am (t1/2 = 432 y), 243

Am (t1/2 = 7370 y)] can be

transmuted into radionuclides with a much shorter-half life, which is important for the end of

the nuclear fuel cycle. However, the separation of these minor actinides from other fission

products, such as lanthanides, remains a difficult problem. The additional separation of

AmIII

/CmIII

is a great challenge due to their similar chemical properties and ionic radii.

Phosphine oxide ligands have recently demonstrated relatively high selectivity for the Am-

Cm pair in the form of (Ph2PyPO)2M(NO3)3.22

Although phosphine oxides are heavily

utilized in separation of f-elements relevant to the nuclear fuel cycle, there have been few

crystallographic studies for trans-uranium elements, and indeed only the mono and bis[Opy-

2,6-CH2(Ph)2PO], NOPOPO, adducts has been reported.23

Herein we examine the synthesis

and structure in saturated tri-cyclohexylphosphine oxide adducts of f-element tribromides,

and the effects of the ITI on tri-valent f-elements.

Figure 1. General depiction of ligand designations in mer-MX3L3.

4

Experimental Details

General Considerations. Caution! 243

Am (t1/2 = 7,364 years) and its daughters have high

specific activity α-particle and, γ emitting radionuclides, and its use presents extreme hazards

to human health. This research was conducted in radiological and nuclear facilities with

appropriate analyses of these hazards and implementation of controls for the safe handling

and manipulation of these toxic and radioactive materials.

Materials. All experiments were conducted in air with no attempt to exclude air or water.

Reagents and solvents, OPcy3 (cy = cyclohexyl, C6H11, Alfa Aesar), CDCl3 (Cambridge),

iPrOH (Sigma) NH3(aq) (Baker) were purchased from commercial sources and used as

received. LnBr3•6H2O (Ln = La – Nd) were synthesized by dissolution of Ln2O3 in

concentrated HBr and heated at 150 °C in a box furnace until viscous, then agitated, stirred

until cooled to room temperature, dissolved in water and boiled down. This process was

repeated twice. The product was washed with ether, to remove residual acid and Br2, until

washings were colorless, dried under house vacuum for 10-15 min and stored in a desiccator

and used with the assumed hydration number of six. All 243

Am synthetic manipulations were

performed in a certified chemical fume hood, and a known concentration stock solution was

prepared as previously described.24

Aqueous manipulations were performed with >18 Ω

water from a Millipore purification system.

Instrumentation. All 1H,

13C{

1H} and

31P{

1H} NMR spectra were recorded at 294(2) K on a

Bruker 600 MHz NMR spectrometer operating at 600.13, 150.90, and 242.94 MHz,

respectively, for all lanthanide samples; the sample of 243

AmBr3(OPcy3)3 was recorded at

295(2) K on a Bruker 400 MHz NMR spectrometer operating at 400.17, 100.62, and 161.99

MHz, respectively. 1H and

13C{

1H} were referenced to internal solvent resonances,

31P{

1H}

spectra were referenced externally to 85% H3PO4. For radiologic containment,

243AmBr3(OPcy3)3 was dissolved in minimal CDCl3, transferred to a PTFE NMR tube liner,

5

sealed, checked for contamination, placed inside a high quality borosilicate NMR tube, and

checked again for contamination before being transported to the spectrometer. Due to the

paramagnetism of Am3+

, Ce3+

, Pr3+

and Nd3+

, and in particular the small sample size of

243AmBr3(OPcy3)3, only unambiguously identifiable peaks are assigned. Single crystal

UV/vis/NIR measurements were made using a CRAIC microphotospectrometer on single

crystals from 320 to 1700 nm. Single crystals of the lanthanide complexes were mounted on

nylon cryoloops with Paratone-N oil. Crystals of 243

AmBr3(OPcy3)3 was mounted with

appropriate layers of containment. Crystallographic data from all single crystals were

collected on a Bruker D8 Quest diffractometer with a Photon 100 complementary metal-

oxide-semiconductor (CMOS) detector, and cooled to 120(2) or 130(2) K using an Oxford

Cryostream or CRYO Industries low-temperature device. The instrument was equipped with

graphite monochromatized Mo Kα X-ray source (λ = 0.71073 Å). The APEX325

program

package was used to determine the unit-cell parameters and for data collection. The raw

frame data was processed using SAINT26

and SADABS27

to yield the reflection data file.

Subsequent calculations were carried out using the SHELXTL28, 29

or OLEX230

programs.

Theoretical Methods. The coordinates of MBr3(OPcy3)3 (M = Am, Ce, Nd) for the

calculations were obtained directly from the crystal structure to keep the constraints imposed

by the solid-state packing. To utilize multiconfigurational calculations, the complete active

space self-consistent field (CASSCF) approximation31

was used as implemented in the

ORCA 4.1.1 program.32

Wave functions were obtained utilizing the SARC-TZVP basis set

for the metal centers and the Def2-TZVP basis functions for the rest of the atoms. The active

space considered were n electrons (n = 1, 3, 6 for Ce, Nd, and Am) in the seven f orbitals

giving rise to a CAS(n,7). Scalar relativistic effects were included by the second-order

Douglas-Kroll-Hess (DKH2) Hamiltonian. State interactions via quasi-degenerate

perturbation theory (QDPT) were used to correct the wave function for spin-orbit coupling

6

(SOC). The resulting wave functions (SO-CAS) were used to analyze the nature of the

ground and low-lying excited states, whereas the scalar relativistic wave functions (SR-CAS)

were used for further bonding analysis.

The nature of the chemical bonds was addressed performing a topological analysis of

the electron density using Bader’s quantum theory of atoms in molecules (QTAIM) analysis.

Key elements within QTAIM were extracted such as the electron density, delocalization

indices, and energy densities at the interatomic region (bond critical point, BCP) which have

been employed previously for this aim.33-41

The covalency was analyzed, on one hand, by

changes in the concentration of the electron density at the BCP along with changes in the

delocalization indices. On the other hand, energy densities show the polarization of the

covalent bond by looking at the ratios between potential [V(r)] and kinetic [G(r)] energy

densities, which for partial covalent bonds lie in between values of 1 and 2. The total energy

density shows the degree of covalency that is represented by the level of predominance of the

potential over the kinetic energy density.42

A model system was also investigated where the cyclohexyl groups were replaced by

methyl groups to simplify the molecular orbital energy diagram picture and allow the

observations between the Am, Ce and Nd complexes to be made. The methyl groups were re-

optimized while the rest of the molecule was kept frozen to conserve the crystal structure of

the metal surrounding atoms. These calculations were performed in the ADF2019 suite43, 44

using the PBE functional along with the TZP basis set. Frozen-core and all-electron

calculations were performed for the full structure to prove the role of 5/6p orbitals in the

stabilization of the complexes at the same level of theory. Additionally, ligand-field DFT45, 46

was used to examine the reduction of the inter–electronic repulsion within the 5/6p shell due

to central-field and symmetry-restricted covalency. The procedure used herein has been

previously described for Cs2KYF6:Pr3+

,45

where occupation numbers in the f-shell were

7

allowed to be fractional. The reductions were obtained not only with respect to the free-ions

but also compared to the nona-aquo complexes, [M(H2O)9]3+

, where the geometries were

taken from the crystalized structures in the literature.47-49

Synthesis of 243

AmBr3(OPcy3)3. An aliquot of 243

Am (3.0 mg, 12 µmol) was drawn from a 2

M HCl stock solution and precipitated with excess NH3(aq) to give a pale yellow solid naïvely

formulated as Am(OH)3, washed with water (2 × 2 mL), suspended in ~ 1 mL of water and

dissolved with HBr (concentrated, ~0.5 mL) to give a yellow solution. The yellow solution

was transferred to a 20 mL scintillation vial, placed under a heat lamp and gently evaporated

to a yellow residue formulated as AmBr3•nH2O. The residue was dissolved in iPrOH (1.50

mL) to give a dark yellow solution. A colorless solution of OPcy3 (11 mg, 38 µmol) in iPrOH

(1.00 mL) was added to the Am solution, which quickly became turbid and clear again. The

solution was capped and left to stand undisturbed. Over 3 h amber colored X-ray quality

crystals were deposited. A small sample was withdrawn for spectroscopy (single crystal X-

ray diffraction and solid state UV/vis/NIR). The solution was capped and left to stand for 3

days to allow further crystallization. The mother liquor was decanted, washed with Et2O (3 ×

0.5 mL), dried in air and transferred to a glovebox dedicated to actinide chemistry to give

AmBr3(OPcy3)3 as a yellow/brown crystalline solid, 9.0 mg, 54%. 1H NMR (CDCl3; 400

MHz) δ: 1.80 (br, s, cy), 1.67 (br, s, cy), 1.39 (br, s, cy), 1.14 (br, s, cy); 13

C{1H} NMR

(CDCl3; 101 MHz) δ: 27.08 (2JPC = 27 Hz, cy), 26.15 (cy) 25.90 (cy);

31P{

1H} NMR (CDCl3;

162 MHz) δ: 108.89 (s, ν1/2 141.1 Hz). Due to the weak paramagnetism and small sample

size 1H integration is ambiguous and

1H and

13C{

1H} peak assignments are tentative, see ESI.

UV/vis/NIR [λmax, nm (cm−1

), single crystal]: 340.0 nm (29,411) charge transfer, 368.4

(27,148) 5G2′, 380.9 (26,252)

5G4′, 433.4 (23,074)

5H4′, 457.5 (21,856)

5G2′, 477.0 (20,695)

5D2′, 508.0 (19,685)

5L6′, 524.2 (19,075)

5L6′, 777.4 (12,863)

7F6′, 805.8 (12,422)

7F6′, 823.2

(12,147) 7F6′, 1042.6 (9591)

7F4′.

8

General Synthesis of LnBr3(OPcy3)3, (Ln = La, Ce, Pr, Nd). As an alternative to the

literature50

a colorless solution of OPcy3 (18 mg, 61 µmol) in iPrOH (1.0 mL) was added to a

yellow solution of LnBr3•6H2O (~10 mg, ~20 µmol) in iPrOH (1.5 mL) causing the solution

to become turbid and then clear. The vial was capped and left to stand overnight during

which colorless X-ray quality crystals were deposited. A small sample was withdrawn for

spectroscopy (single crystal X-ray diffraction and solid state UV/vis/NIR). The mother liquor

was decanted, washed with Et2O (3 × 0.5 mL), dried in air and briefly dried under reduced

pressure to give LnBr3(OPcy3)3 as a crystalline solid. All products were confirmed by single

crystal X-ray crystallography.

LaBr3(OPcy3)3. Colorless LaBr3(OPcy3)3 20 mg, 80%. 1H NMR (CDCl3; 600 MHz) δ: 4.305

(s, 2H, H2O), 2.068 (m, 8H, cy), 1.991 (m, 18H, cy), 1.842 (m, 18H, cy), 1.700 (m, 9H, cy),

1.600 (m, 18H, cy), 1.352 – 1.261 (m, 28H, cy); 13

C{1H} NMR (CDCl3; 151 MHz) δ: 34.772

(1JCP = 34.8 Hz, i-cy), 26.893 (

2JCP = 26.94 Hz, cy), 25.996 (cy), 25.901 (cy);

31P{

1H} NMR

(CDCl3; 243 MHz) δ: 60.314 (s, ν1/2 151.9 Hz).

CeBr3(OPcy3)3. Orange CeBr3(OPcy3)3 20 mg, 75%. 1H NMR (CDCl3; 600 MHz) δ: 5.29

(br, s, 9H, cy), 3.64 (br, s, 18H, cy), 2.68 (br, s, 18H, cy), 2.01 (s, 18H, cy), 1.82 (s, 25H, cy),

1.22 (br, s, 10H, cy); 13

C{1H} NMR (CDCl3; 151 MHz) δ: 38.76 (

1JCP = 38.8 Hz, i-cy), 27.51

(cy), 26.06 (cy); 31

P{1H} NMR (CDCl3; 243 MHz) δ: 109.48 (s, ν1/2 240.4 Hz). UV/vis/NIR

[λmax, nm (cm−1

), single crystal]: 339.8 (29,479) charge transfer.

PrBr3(OPcy3)3. Colorless PrBr3(OPcy3)3 22 mg, 83%. 1H NMR (CDCl3; 600 MHz) δ: 20.85

(br, s, ν1/2 = 1468 Hz, 5H, cy), 13.55 (br, s, ν1/2 = 862 Hz, 16H, cy), 10.52 (br, s, ν1/2 = 926

Hz, 14H, cy), 4.8 (br, s, 20H, cy), 3.40 (br, s, 21H, cy), 2.72 (br, s, 12H, cy), 1.44 (br, s, 11H,

cy); 13

C{1H} NMR (CDCl3; 151 MHz) δ: 36.94 (cy), 30.54 (cy), 27.70 (cy);

31P{

1H} NMR

(CDCl3; 243 MHz) δ: 212.4 (s, br, ν1/2 4290).

9

NdBr3(OPcy3)3. Pale green NdBr3(OPcy3)3 19 mg, 82%. 1H NMR (CDCl3; 600 MHz) δ:

11.77 (br, s, ν1/2 = 590 Hz, 8H, cy), 7.39 (br, s, ν1/2 = 320Hz, 17H, cy, overlapping with

CDCl3), 5.53 (br, s, ν1/2 = 400 Hz, 17H, cy), 3.05 (br, s, 18H, cy), 2.53 (br, s, 19H, cy), 2.14

(br, s, ν1/2 = 11H, cy), 1.21 (br, s, 11H, cy); 13

C{1H} NMR (CDCl3; 151 MHz) δ: 30.95 (cy),

28.54 (cy), 26.66 (cy); 31

P{1H} NMR (CDCl3; 243 MHz) δ: 190.2 (s, br, ν1/2 1366 Hz).

UV/vis/NIR [λmax, nm (cm−1

), single crystal]: 532.0 (18,798), 572.8 (17,459), 576.6 (17,342),

584.3 (17,114), 588.1 (17,003), 591.9 (16,893), 595.0 (16,806), 599.6 (16,678), 607.3

(16,467) all excitations belong to 4G7/2,

4G5/2.

Results and Discussion

Synthesis. Previously published literature on LnCl3(OPR3)x show that the products have poor

solubility or are prone to speciation.51-53

The more solubilizing bromide anion was studied

instead. The known mer-LnBr3(OPcy3)3 (mer = meridional; cy = cyclohexyl, C6H11) have

been recently reported and give opportunity for extension to the trivalent actinides, though

small lanthanides can speciate.50, 54-56

There has been just one report of a single crystal Am–

Br compound, AmBr3(THF)4.57

The previously reported syntheses of mer-LnBr3(OPcy)3, (cy = cyclohexyl, C6H11)

utilized boiling ethanol and describe the complexes as having low solubility.50

By changing

the alcohol to iso-propyl alcohol (iPrOH) and working on a scale relevant to actinides, ie ≤

0.02 mmol of metal content, a smooth synthesis is obtained. This was extended to americium

by starting from a stock solution of AmCl3•nH2O in HCl, precipitating the hydroxide and

dissolving the product in HBr(aq) and evaporated to dryness forming a putative AmBr3•nH2O.

Combining the components in iPrOH initially forms a turbid solution which clarified within

minutes and upon standing at room temperature, amber colored X-ray quality crystals formed

10

within 2 h, Equation 2. A small sample was removed for spectroscopy and the solution was

left to stand several days to increase the crystalline yield before work up, Figure 2.

Figure 2. Thermal ellipsoid plot of AmBr3(OPcy3)3 drawn at the 50% probability level with

hydrogen atoms omitted for clarity.

Crystallography. AmBr3(OPcy3)3 crystallizes as the meridional isomer, mer-

AmBr3(OPcy3)3, in the orthorhombic Pca21 space group and is isomorphous with its

lanthanide analogs.25

Based on the Flack parameter, a small (≤ 3%) enantiomorphic twin was

dealt with using a TWIN/BASF refinement, see ESI.58

The Am–Br bond lengths fall into two

Am1

Br3

Br1

Br2

O1 O2

O3

P1 P2

P3

11

classes, that of axial (ax) and equatorial (eq) ligands, where axial ligands consistent of a

homo-ligand trans to the ligand of interest, and equatorial ligands where a hetero ligand is

trans to the ligand of interest, Figure 1. The Am–Oax bond lengths are 2.302(7), and 2.312(7)

Å while the Am–Oeq bond is 2.349(6) Å, a separation of 3σ. The Am–Brax atoms display a

bond distance of 2.870(1), and 2.882(1) Å and the Breq atom displays a significantly longer

distance of 2.912(1) Å. These values are all significantly longer than the 2.8222(6),

2.8445(6), and 2.8610(6) Å bond lengths reported in AmBr3(THF)4.57

However, all of the

2.466(4)–2.533(4) Å Am–OTHF bond lengths in AmBr3(THF)4 are significantly longer than

Am–O bond lengths in AmBr3(OPcy3)3. The 2.34(1)–2.51(1) Å Am–O bond lengths reported

for the NOPOPO ligand in Am(NOPOPO)(NO3)3 and [Am(NOPOPO)2(NO3)][NO3]2

[NOPOP = Bis[(phosphino)methyl]pyridine-1-oxide, Opy-2,6-CH2(Ph)2PO] are only

comparable to 2.349(6) Å Am–Oeq bond since the Am–Oax bond lengths are all significantly

shorter, Table 1.23

All of the X–Am–Y bond angles are between 85.2(2)–95.60(5)° for cis

ligands and 172.74(3)–178.1(2)° for trans ligands, see ESI.

Table 1. Comparisons of Am–O bond lengths (Å) in selected Am complexes.

Am–OPcy3ax Am-OPcy3eq Am–ONL Am–OPL

AmBr3(OPcy3)3 2.302(7), 2.312(7) 2.349(6)

Am(L)(NO3)323

2.417(9) 2.38(1), 2.39(1)

[Am(L)2(NO3)][NO3]223

2.51(1)

2.506(9)

2.39(1), 2.34(1),

2.38(1), 2.34(1)

L = NOPOPO, Opy-2,6-CH2(Ph)2PO

In the course of preparing the synthesis of mer-AmBr3(OPcy3)3, the analogous

lanthanides, La–Nd, were examined using the modified synthesis stated above, since the 6-

coordinate radius of Am3+

, 0.975 Å, is most closely related to Nd3+

, 0.983 Å.59

It was found

12

that the Nd and Pr analogs, mer-LnBr3(OPcy3)3, are isomorphous with the previously

reported structures, except the half occupied lattice water was not located in our structures,

see ESI.50

The Ce analog, mer-CeBr3(OPcy3)3 is not yet reported and the structure was

collected. The La analog was reported in the P21 space group with a lattice ethanol molecule,

mer-LaBr3(OPcy3)3•EtOH, however upon synthesis in iPrOH, the isomorphous Pca21 unit

cell was obtained and is reported here, see ESI. Crystals of CeBr3(OPcy3)3 are orange, while

crystals of the La, Pr and Nd analogs are all colorless. Bulk samples of PrBr3(OPcy3)3 and

NdBr3(OPcy3)3 are pale yellow and pale green, respectively. The bond metrics of the

lanthanides examined here all display the same axial/equatorial bonding patterns, that being

axial ligands display much shorter bond lengths than equatorial ligands, with distorted

octahedral geometries, see ESI.

With this data in hand, the calculations of ITI effect from Eq. 1 were carried out on

the MBr3(OPcy3)3 (M = Am, La, Ce, Pr, Nd) complexes examined here. The data show that a

subtle increase in ITI effect is seen with decreasing ionic radius, Table 2, all of the data are

within the error of one another. When the ITI calculations were repeated using the

crystallographic data for the previously published LnBr3(OPcy3)3 compounds (Ln = La, Pr,

Nd, Gd, Ho), as well as LnI3(Et2O)3,20

LnCl3(HMPA)3,60-62

and the series YbX3(THF)3 (X

= Cl, Br, I).11, 63, 64

The data shows no clear trends or patterns with respect to lanthanide or

halide identity, where the halide ligands usually show no ITI. The oxygen donors follow the

pattern in terms of ITI values where: Et2O > THF > HMPA, which appears counter intuitive

since HMPA is regarded as a strong donor, while Et2O is regarded as a weak donor, see ESI

for data tables. Without more sophisticated investigations and based on these small data sets,

it is not clear what ligands affect the values for ITI calculations in terms of donor strength,

steric bulk and crystallization effects. No analogous actinide compounds were located, likely

13

due to the prevalence of the +4 oxidation state in the early actinides and the scarcity of trans-

plutonium crystallographic data.

Table 2. Inverse trans influence calculated from Eq. 1 for the MBr3(OPcy3)3 (M = Am, Nd,

Pr, Ce, La) series.6

MBr3(OPcy3)3 Am Nd Pr Ce La

Radius (Å)a 0.975 0.983 0.99 1.01 1.032

ITIM–Br 98.8(2) 98.9(2) 98.8(2) 99.0(2) 99.1(1)

ITIM–O 98.2(2) 98.6(3) 98.4(2) 98.6(1) 99.0(3)

a6-Coordinate Shannon Ionic Radius

Electronic Absorption Spectroscopy. The electronic absorption spectroscopy for

AmBr3(OPcy3)3 shows an intense charge transfer band centered at λmax 340 nm (29,411

cm−1

) in addition to the Laporte forbidden 5f → 5f transitions characteristic of AmIII

.65, 66

With few exceptions, the energies of the absorptions are similar to those reported in the low

temperature spectrum of AmBr3 and the recently reported spectrum of (PPh4)3AmCl6.67

The

characteristic 5L6′ excitation reported at 510 nm (19,588 cm

–1) shifted to 508 nm (19,685 cm

–

1), Figure 3. The compound was not fluorescent at room temperature even with long

integration times (≤ 2000 ms) at an excitation wavelength of 365 or 420 nm. CeBr3(OPcy3)3

displays an intense charge transfer band with λmax of 339 nm (29,479 cm–1

). NdBr3(OPcy3)3

reveals, sharp hypersensitive transitions of low intensity between 500–607 nm consistent with

the 4G7/2 and

4G5/2 excitations, similar to the values reported for NdBr3(g) at 1195 °C, while

several of the typical 4f → 4f transitions reported for Nd(ClO4)3(aq) were not observed.68-70

LaBr3(OPcy3)3 and PrBr3(OPcy3)3 gave no UV/vis/NIR peaks between 320–1700 nm. The

former is typical of the 5d04f

0 La

3+ ion, while the latter is unusual for the 4f

2 Pr

3+ ion,

70 this

14

may be due to the pseudo inversion center present in MBr3(OPcy3)3. Though the Pr3+

ion

possesses hypersensitive 3P2 and

1D2 transitions at 444.4 nm (22,500cm

−1) and 588.2 nm

(17,000 cm–1

), respectively, but were not observed through repeated collections, see ESI for

spectra.69, 70

None of the lanthanide compounds were fluorescent.

Figure 3. Solid state UV/vis/NIR of AmBr3(OPcy3)3 at room temperature, with excitation

assignments and photograph of crystals.

Multi-nuclear NMR Spectroscopy. In order to gain more insight into the system, and due to

the convenient spectroscopic handle provided by the 31

P nucleus, 1H,

13C{

1H} and

31P{

1H}

multi nuclear NMR spectra were recorded. Due to radiological constraints and small sample

sizes obtaining NMR spectra on americium samples can be difficult. Exceptions have

included Evans' Method studies,71

a notable solid state MAS study of AmO272

and the recent

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

300 400 500 600 700 800 900 1000 1100 1200

Ab

sorb

an

ce

Wavelength (nm)

7F4′

7F6′

5L6′

5L6′

5D2′

5G2′

5H4′

5G2′

5G4′

15

report of Am(C5Me4H)3.73

Some 31

P{1H} data has been reported previously for other

LnBr3(OPcy3)3 complexes,50

here we seek to add to this data and compare it with its

americium analog. Because of the weak paramagnetism of the 5f 6

Am3+

ion, 1.64 µB,71

a

shorter relaxation time (d1 = 1 sec) was utilized along with several extra scans to obtain a

good signal for AmBr3(OPcy3)3 at a shift of δ 108.89 ppm, Figure 4. To the best of our

knowledge this is the first report of a 31

P NMR signal in an americium complex. The signal is

similar in chemical shift to the 4f 1

CeBr3(OPcy3)3 at δ 109.48 ppm. Both signals are shifted

down field from the diamagnetic LaBr3(OPcy3)3 (δ 60.314 ppm) and the free ligand OPcy3

(δ 50.574 ppm) which was recorded for comparison. The more paramagnetic 4f 2

and 4f 3

PrBr3(OPcy3)3 and NdBr3(OPcy3)3 are significantly shifted further down field (δ 212.4 and

190.2 ppm, respectively) and are significantly broadened (4290 and 1366 Hz, respectively),

Figure 4. Due to the high fluxionality of the cyclohexyl rings the 1H NMR spectra are

complicated and provide limited information. In particular the paramagnetism in

PrBr3(OPcy3)3 and NdBr3(OPcy3)3 give rise to several broad peaks over a range of about 20

ppm, some with widths over 1400 Hz, see ESI for spectra. The 13

C{1H} NMR spectra of

MBr3(OPcy3)3 show several signals and are consistent with a single chemical environment

for the carbons. Due to the small sample size of AmBr3(OPcy3)3 only three of the expected

four signals were observed, with the ipso-carbon likely being too broad and weak to be

observed in this experiment, though a doublet at δ 27.08 ppm with JCP coupling constant of

27 Hz is consistent with the carbon α to the ipso-carbon. For the diamagnetic free ligand and

LaBr3(OPcy3)3 both 1-bond and 2-bond C-P coupling was observed with constants of ca 35

and 27 Hz, respectively. While only the 1-bond C-P coupling was observed in

CeBr3(OPcy3)3 and no coupling was observed in the Pr and Nd compounds, see ESI for

spectra.

16

Figure 4. Stacked 31

P{1H} NMR spectra of MBr3(OPcy3)3 (M = Am, Nd, Pr, Ce, La)

including OPcy3 in CDCl3 at 298-294 K.

Theoretical Analysis

Bonding Analysis. To obtain a deeper understanding of the bonding in MBr3(OPcy3)3, a

Quantum Theory of Atoms In Molecules (QTAIM) analysis was performed to calculate the

concentration of electron density ρ(r), delocalization indices δ(r), and energy densities

[potential, V(r), kinetic, G(r), and total energy densities, H(r)]. All of these metrics are

utilized to determine the degree of covalency exhibited in the bonding interactions. Based on

previous studies where the nature of bonding interactions of f-block complexes has been

shown that bonds are not formally covalent, but rather partially covalent.39, 40, 74

A partial

covalent bond implies positive values for the Laplacian of the electron density, ∇ρ(r), and

negative values for total energy densities, H(r). Here, the term "covalency" refers to the

Am

Nd

Pr

Ce

La

OPcy3

17

metal–ligand interaction needed to experience orbital overlap, which is reflected by the

buildup of electron density [ρ(r)] in the interatomic region. Furthermore, covalency can be

enhanced by a better energy match between the atomic orbital involved, which is reflected by

the delocalization of the electrons in the interatomic region.

Figure 5. QTAIM metrics of the Bond Critical Points (BCPs) derived from the SR-CAS(n,7)

wave functions, (a, Left) Concentration of the electron density, (b, Right) delocalization

indices, and (c) total energy densities. See ESI for exact numbers.

From a general perspective the results herein show that the M–Br bonds displays a

low concentration of electron density in the interatomic region compared to the M–O bonds,

Figure 5a, though similar delocalization indices, Figure 5b, implying that the covalency in

the M–O bonds occur due to increased orbital overlap, whereas the better energy match

between parent metal–ligand orbitals for the M–Br bonds compensate for the lack of electron

density concentration. A more subtle difference is observed in the energy density of the M–O

bonds, particularly the M–O(3) bond where CeBr3(OPcy3)3 most resembles AmBr3(OPcy3)3.

Whereas the M–Br bonds of CeBr3(OPcy3)3 and NdBr3(OPcy3)3 are closer to each other,

18

Figure 6a. The origin of these subtleties resides in the balance between kinetic, G(r), and

potential energy, V(r), densities with respect to the Laplacian of the electron density, ∇ρ(r),

where a more careful treatment can be done when the total electron densities, H(r), is

normalized by the electron density at the Bond Critical Point (BCP). This allows the role of

the kinetic, G(r), and potential energies, V(r), to be isolated from the concentration of

electron density, ρ(r), Figure 6b. When the data are compared, the same trends are observed.

It appears that CeBr3(OPcy3)3 and NdBr3(OPcy3)3 differ from each other in that: the

bonding patterns are independent of the concentration of electron density, ρ(r), i.e. Ce

stabilizes the electrons in the interatomic region similarly to Nd when a more polarizable

ligand is present like Br, while Ce resembles Am when a harder-donor ligand is present, like

OPR3. Moreover, the dominance of potential energy, V(r), over kinetic energy, G(r) is

independent of the electron density, which shows that the covalent contribution in Nd–O(3)

bond is almost negligible, Figure 6b.

Figure 6. Total energy density over the electron density at the BCP derived from a SR-

CAS(7,7) wave function. See ESI for exact numbers.

19

Table 3. Ratio between potential [V(r)] and kinetic [G(r)] energy densities.

|V(r)|/G(r) (kJ mol

−1 Å

−3)

Ce Nd Am

M(1)-Br(1) 1.10 1.10 1.13

M(1)-Br(2) 1.11 1.10 1.14

M(1)-Br(3) 1.09 1.09 1.12

M(1)-O(1) 1.05 1.04 1.04

M(1)-O(2) 1.05 1.04 1.04

M(1)-O(3) 1.03 1.02 1.02

Further characterization of the bonds is provided by the ratio between potential, V(r),

and kinetic, G(r), energy densities, that shows the extent of the polarization of the bond, again

the M–Br bonds are less polarized than the M–O bonds, where Am shows the least polarized

bonds (down to 86% of polarization), Table 3. This agrees with the better energy match

provided by Br− with the lanthanides and actinides, but is most pronounced in the Am

complex.

20

Figure 7. Molecular orbital (MO) energy level diagram for MBr3(OPMe3)3 (M = Am, Ce,

Nd) from a scalar relativistic PBE/TZVP calculation. MO labels correspond to the

predominant shell in the MO, for the MO composition see Tables S2-S4. MO depictions

correspond to the involvement of the semi-core 5/6p orbitals in orbital mixing.

Qualitatively, the ITI correlates with the previous bonding analysis.21

However,

quantitatively, this does not appear to be the case due to the simple shortening of the bond,

which could imply different effects operating simultaneously in the complex. Another way to

corroborate the presence of the ITI is by the inclusion of the 5/6p orbitals in an all-electron

versus a frozen-core calculation .21

Our results show that CeBr3(OPcy3)3 exhibits the highest

amount of stabilization (84.5 kJ/mol) then AmBr3(OPcy3)3 (44.2 kJ/mol), and

NdBr3(OPcy3)3 (35.3 kJ/mol) shows the least amount of stabilization by the inclusion of the

21

5/6p shell, which confirms the presence of the ITI in these systems. However, the energies of

stabilization do not correlate with the trend observed for the ITI percentages coming directly

from the contraction of the bonds in the trans positions. This is not necessarily true for a

system presenting more than one ITI mechanism because they compete within the same

molecule, and therefore become more complicated to analyze. For clarity in the construction

of an MO energy level diagram, the cyclohexyl rings were truncated to methyl groups, e.g.

MBr3(OPMe3)3, Figure 7.75

This mixing is produced with the O 2p and P 3s orbitals,

providing a more delocalized character of the bond and the stronger mixing between 5p

orbitals in Ce is observed, Figure 7.

Another way to show the role of the Ln/An 5/6p orbitals in ITI is to assess the

reduction of the electron repulsion of these semi-core electrons in the complex with respect to

the free-ion. Within ligand field theory (LFT) the one-electron inter-electronic repulsion

integrals are described by the Slater-Condon parameters Fk(nl,nl) (n = shell, l = s,p,d,f) and

the spin-orbit coupling parameter ζnl.76, 77

Previous studies have successfully applied a non-

empirical method to obtain these parameters using a ligand-field DFT (LFDFT) capable of

predicting the electronic structure of lanthanide complexes.45, 78-81

Since the reductions of the

Slater-Condon parameters with respect to the free-ion are related to the central-field and

symmetry-restricted covalency, their evaluation will provide further insight into the nature of

ITI in these complexes.

The reduction of the LF parameters is considerably larger in CeBr3(OPcy3)3

compared to NdBr3(OPcy3)3 and AmBr3(OPcy3)3, whose reductions are similar, Table 4.

These results agree with the stabilization energies obtained between frozen-core to all-

electron calculations, confirming the presence of ITI. This also shows that the sizable

reductions indicate an important covalent component related to the 5/6p orbital involvement

in the interaction between the metal ions and the Br and phosphine oxide ligands.

22

Table 4. Reduction of the Slater-Condon parameters* of the 5/6p semi-core electrons derived

from LF-DFT. Δred refers to the difference between the aquo and MBr3(OPcy)3 (M = Ce, Nd,

Am) complexes.

F2(p,p) (eV) ζ5/6p (eV)

[M(H2O)9]3+

MBr3(OPcy)3 Δred [M(H2O)9]3+

MBr3(OPcy)3 Δred

CeIII

28% 70% 42% 18% 47% 29%

NdIII

21% 43% 22% 15% 28% 13%

AmIII

19% 45% 25% 14% 27% 12%

* See ESI for Slater-Condon parameters

The differences in bonding observed between lanthanides and actinides make the

comparison more complicated due to the involvement of the 5f electrons in the case of

americium, which significantly increases the covalent character of the bond. In this context,

only Ce and Nd could be compared with QTAIM metrics, where delocalization and total

energy densities predict the trend observed in the stabilization energies from the involvement

of the 5p electrons.

Conclusions

The synthesis and characterization of AmBr3(OPcy3)3 has been achieved and shows the same

meridinal coordination geometry as the larger lanthanides. Spectroscopic analysis by single

crystal X-ray diffraction shows that the homo-trans ligands display significantly short bonds

than the hetero-trans ligands. Single crystal UV/vis/NIR spectra show large charge transfer

bands for the Ce and Am complexes and hypersensitive transitions for the Nd and Am

23

analogs due to the pseudo-inversion center. Analysis by 31

P NMR spectroscopy illustrates the

weak paramagnetism of the 5f 6

Am3+

center. Bonding analyses show that the complex

displays a significant inverse trans influence (ITI) with the bonding ligands, though its

mechanism is not directly related to the involvement of the 5/6p electrons. This suggests that

there is an interplay between the involvement of valence electrons that significantly

separates the lanthanides from the actinides. It is surprising that Ce shows the highest amount

of 5p electron involvement in covalency. This is observed by the reduction of the electron–

electron repulsion of the 5p shell compared to the aquo-complex, [Ce(H2O)9]3+

. This study

provides further evidence of ITI in low–valent f-block complexes, and their potential

occurrence in heavier actinides, whose chemistry is dominated by the trivalent oxidation

state. Furthermore, it constitutes a new feature that can be exploited for rational ligand design

in order to achieve selective ligands for separations in nuclear waste treatment.

Conflicts of interest

The authors declare no competing financial interest

Acknowledgements

We thank the support of the U.S. Department of Energy, Office of Science, Office of Basic

Energy Sciences, Heavy Element Chemistry program under Award Number DE-FG02-

13ER16414. The isotopes used in this research were supplied by the U.S. Department of

Energy Isotope Program, managed by the Office of Science for Nuclear Physics. We thank

Benjamin W. Stein and Conrad A. P. Goodwin of Los Alamos National Laboratory for

helpful discussions. We are grateful to Dr. Banghao Chen for his assistance with the NMR

experiments. We thank Jason Johnson and Ashley Gray of Florida State University for

radiological assistance.

24

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28

78. H. Ramanantoanina, W. Urland, B. Herden, F. Cimpoesu and C. Daul, Phys. Chem.

Chem. Phys., 2015, 17, 9116-9125.

79. H. Ramanantoanina, M. Sahnoun, A. Barbiero, M. Ferbinteanu and F. Cimpoesu, Phys.

Chem. Chem. Phys., 2015, 17, 18547-18557.

80. H. Ramanantoanina, W. Urland, A. García-Fuente, F. Cimpoesu and C. Daul, Chem.

Phys. Lett., 2013, 588, 260-266.

81. H. Ramanantoanina, F. Cimpoesu, C. Göttel, M. Sahnoun, B. Herden, M. Suta, C.

Wickleder, W. Urland and C. Daul, Inorg. Chem., 2015, 54, 8319-8326.

29

TOC Image

La

Ce

Pr

Nd

Am

download fileview on ChemRxivAmBrOPcy_ChemRxiv.pdf (1.07 MiB)



S1

Electronic Supporting Information for

Probing the inverse trans influence in americium and lanthanide

tribromide tris(tricyclohexylphosphine oxide)

Cory J. Windorff, Cristian Celis-Barros, Joseph M. Sperling, Bonnie E. Klamm, Noah C.

McKinnon, Thomas E. Albrecht–Schmitt*

Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, RM.

118 DLC, Tallahassee, Florida 32306, USA. E-mail: [email protected];

Table of Contents

PHOTOGRAPHS OF AMERICIUM SYNTHESIS……………………………………………..S2

SOLID STATE UV/VIS/NIR SPECTRA WITH PICTURES OF COMPOUNDS…………………S3

MULTI NUCLEAR NMR SPECTRA……………………………………………………...S4-S14

THEORETICAL CALCULATIONS.………………………………………………………S15-S19

ADDITIONAL ITI CALCULATIONS………………………………………………………S20

CRYSTALLOGRAPHY…………………………………………………………………..S21-S33

REFERENCES…………………………………………………………………………….S34

mailto:[email protected]

S2

PHOTOGRAPHS OF AMERICIUM SYNTHESIS

Figure S1. Photograph of AmBr3(OPcy3)3 in iPrOH (left) and 9.0 mg of crystalline material

(Right).

Figure S2. Photograph of AmBr3(OPcy3)3 NMR sample in CDCl3 (left), and additional

photograph of isolated crystals (right).

S3

UV/VIS/NIR SPECTROSCOPY

Figure S3. Solid state UV/vis/NIR spectra of LnBr3(OPcy3)3 [Ln = La (gray), Ce (orange), Pr (blue), Nd (green)] at room temperature.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

325 350 375 400 425 450 475 500 525 550 575 600 625 650 675 700

Ab

sorb

an

ce

Wavelength (nm)

LnBr3(OPcy3)3

LaBr3(OPcy3)3

CeBr3(OPcy3)3

PrBr3(OPcy3)3

NdBr3(OPcy3)3

4G7/2

4G7/2,

4G5/2

S4

MULTI NUCLEAR NMR SPECTROSCOPY

Figure S4. 1H NMR spectrum of AmBr3(OPcy3)3 in CDCl3 at 295 K with expansion of 8 – 0 ppm region, Because the chemical identity of the

peaks is unclear the peaks are integrated relative to one another with the smallest integrated set to 1.

CHCl3

CHCl3

S5

Figure S5. 13

C{1H} NMR spectrum of AmBr3(OPcy3)3 in CDCl3 at 295 K with expansion of 80 – 15 ppm region.

S6

Figure S6. 31

P{1H} NMR spectrum of AmBr3(OPcy3)3 in CDCl3 at 295 K.

S7

Figure S7. Multinuclear NMR spectra of AmBr3(OPcy3)3 at 295 K in CDCl3, 1H (black),

13C{

1H} (red) and

31P{

1H} (green).

S8

Figure S8. Multinuclear NMR spectra of NdBr3(OPcy3)3 at 294 K in CDCl3, 1H (black),

13C{

1H} (red) and

31P{

1H} (green).

S9

Figure S9. Multinuclear NMR spectra of PrBr3(OPcy3)3 at 294 K in CDCl3, 1H (black),

13C{

1H} (red) and

31P{

1H} (green).

S10

Figure S10. Multinuclear NMR spectra of CeBr3(OPcy3)3 at 294 K in CDCl3, 1H (black),

13C{

1H} (red) and

31P{

1H} (green).

S11

Figure S11. Multinuclear NMR spectra of LaBr3(OPcy3)3 at 294 K in CDCl3, 1H (black),

13C{

1H} (red) and

31P{

1H} (green).

S12

Figure S12. Multinuclear NMR spectra of OPcy3 at 298 K in CDCl3, 1H (black),

13C{

1H} (red) and

31P{

1H} (green).

S13

Figure S13. Stacked 13

C{1H} NMR spectra of MBr3(OPcy3)3 (M = Am, Nd, Pr, Ce, La) including OPcy3 in CDCl3 at 298-294 K.

Am

Nd

Pr

Ce

La

OPcy3

S14

Figure S14. Stacked 31

P{1H} NMR spectra of MBr3(OPcy3)3 (M = Am, Nd, Pr, Ce, La) including OPcy3 in CDCl3 at 298-294 K.

Am

Nd

Pr

Ce

La

OPcy3

S15

THEORETICAL CALCULATIONS

Table S1. QTAIM metrics derived from SR-CAS wave functions for MBr3(OPcy)3 (M = Ce, Nd, Am) complexes. With the following

definitions: ρ(r) – electron density, (eÅ−3

), δ(r) – delocalization indices, V(r) – potential energy density (kJmol−1

Å−3

), G(r) – kinetic energy

density (kJmol−1

Å−3

), and H(r) – total energy density (kJmol−1

Å−3

). H(r)/ ρ(r) represents a "normalized" energy density per electron (kJmol−1

).

ρ(r) δ(r) V(r) G(r)

Ce Nd Am Ce Nd Am Ce Nd Am Ce Nd Am

M(1)-Br(1) 0.2571 0.2693 0.2834 0.3215 0.3172 0.3515 −556.2 −600.1 −666.8 505.3 547.4 589.6

M(1)-Br(2) 0.2618 0.2645 0.2895 0.3209 0.3173 0.3519 −570.3 −586.0 −686.1 515.9 535.2 603.6

M(1)-Br(3) 0.2463 0.2517 0.2686 0.3140 0.3087 0.3399 −522.9 −547.4 −619.4 479.0 503.6 551.0

M(1)-O(1) 0.4090 0.4252 0.4387 0.2950 0.2925 0.3094 −1366.9 −1484.4 −1595.0 1305.4 1426.5 1531.8

M(1)-O(2) 0.4076 0.4184 0.4468 0.2926 0.2862 0.3170 −1354.6 −1444.1 −1642.3 1291.4 1389.7 1573.9

M(1)-O(3) 0.3732 0.3779 0.3982 0.2682 0.2597 0.2834 −1207.2 −1259.8 −1391.4 1175.6 1240.5 1359.8

|V(r)|/G(r) H(r) H(r)/ρ(r)

Ce Nd Am Ce Nd Am Ce Nd Am

M(1)-Br(1) 1.10 1.10 1.13 −50.9 −52.6 −77.2 −197.9 −195.5 −272.4

M(1)-Br(2) 1.11 1.10 1.14 −54.4 −50.9 −82.5 −207.7 −192.3 −284.8

M(1)-Br(3) 1.09 1.09 1.12 −43.9 −43.9 −68.4 −178.1 −174.3 −254.8

M(1)-O(1) 1.05 1.04 1.04 −61.4 −57.9 −63.2 −150.2 −136.2 −144.0

M(1)-O(2) 1.05 1.04 1.04 −63.2 −54.4 −68.4 −155.0 −130.0 −153.2

M(1)-O(3) 1.03 1.02 1.02 −31.6 −19.3 −31.6 −84.6 −51.1 −79.3

S16

Table S2. Molecular orbital (MO) composition of AmBr3(OPMe3)3 for the following orbital

populations: Am – 6p, 5f, 6d; O – 2s, 2p; Br – 4s, 4p; P – 3s, 3p. Percentages in bold

represent the main contribution to the MO. Energies given are relative to the first O 2s MO.

E(eV) Molecular orbital composition

Am 6p Am 5f Am 6d O 2s O 2p Br 4s Br 4p P 3s P 3p

0.0 14%

66%

8% 4%

0.1 6%

69% 3%

11% 5%

0.4

73% 3%

11% 5%

2.6 96%

1%

2.7 89%

1% 3%

2%

2.8 78%

5% 7%

5%

8.1

100%

8.3

100%

8.4 2%

97%

14.7

31%

14.8

42%

10%

15.4

5% 40%

5%

17.4

3%

64%

17.5

2%

68%

17.7

3%

61%

17.7

68%

17.8

66%

17.9

66%

18.9

4%

84%

19.5

3% 3%

87%

19.7

2% 3%

91%

19.8

6% 3%

88%

19.9

3%

93%

20.0

2%

92%

20.0

4%

91%

20.0

2%

92%

20.3

2%

97%

22.2

100%

22.3

95%

1%

22.3

100%

22.3

95%

1%

22.5

89%

4%

22.5

89%

6%

22.5

91%

S17

Table S3. Molecular orbital (MO) composition of CeBr3(OPMe3)3 for the following orbital

populations: Ce – 5p, 4f, 5d; O – 2s, 2p; Br – 4s, 4p; P – 3s, 3p. Percentages in bold represent

the main contribution to the MO. Energies given are relative to the first O 2s MO.

E(eV) Molecular orbital composition

Ce 5p Ce 4f Ce 5d O 2s O 2p Br 4s Br 4p P 3s P 3p

0.0 2%

71% 4%

11% 6%

0.1 4%

72% 2%

10% 6%

0.3

72% 1%

12% 6%

4.6 68%

7%

9%

4.7 70%

4% 1%

7%

4.8 93%

5%

8.2

100%

8.4 2%

96%

8.5 5%

94%

14.7

37%

14.8

4% 44%

4%

15.5

23%

17.3

3%

64%

1%

17.4

2%

68%

1%

17.5

3%

67%

17.6

69%

17.7

69%

17.7

70%

19.1

2%

85%

19.6

1% 4%

89%

19.8

6%

90%

19.9

2%

93%

19.9 2%

94%

20.0

3%

1%

93%

20.0

100%

20.1

1%

95%

20.4

100%

23.5

100%

23.6

100%

23.6

100%

23.6

100%

23.7

89%

2%

23.7

94%

3%

23.7

94%

S18

Table S4. Molecular orbital (MO) composition of NdBr3(OPMe3)3 for the following orbital

populations: Nd – 5p, 4f, 5d; O – 2s, 2p; Br – 4s, 4p; P – 3s, 3p. Percentages in bold

represent the main contribution to the MO. Energies given are relative to the first O 2s MO.

E (eV) Molecular orbital composition

Nd 5p Nd 4f Nd 5d O 2s O 2p Br 4s Br 4p P 3s P 3p

0.0 4%

71% 3%

10% 5%

0.0 6%

70% 1%

10% 4%

0.3

72% 4%

12% 8%

3.6 82%

6%

5%

3.6 89%

3% 1%

3%

3.7 95%

3%

8.2

1%

99%

8.4

97%

8.4 3%

97%

14.8

4%

36%

14.8

4% 42%

4%

15.5 3%

6% 46%

6%

17.3

3%

64%

1%

17.5

2%

69%

1%

17.6

3%

65%

17.7

69%

17.7

68%

17.8

70%

19.1

6%

85%

19.6

2% 4%

88%

19.8

5%

92%

19.9

4% 2%

92%

19.9 2%

94%

20.0

4%

2%

93%

20.0

2%

94%

20.0

95%

20.4

98%

22.3

100%

22.3

100%

22.4

100%

22.4

100%

22.5

93%

2%

22.5

93%

22.5

93%

4%

S19

Table S5. Slater-Condon parameters of the 5/6p semi-core electrons derived from LF-DFT

for the free-ions, [M(H2O)9]3+

, and MBr3(OPcy)3 complexes (M = Ce, Nd, Am).

F2(p,p) (eV) ζ5/6p (eV)

Free-ion [M(H2O)9]3+

MBr3(OPcy)3 Free-ion [M(H2O)9]3+

MBr3(OPcy)3

CeIII

7.715 5.557 2.320 1.774 1.454 0.938

NdIII

7.970 6.259 4.520 2.063 1.754 1.492

AmIII

7.583 6.112 4.207 5.818 4.985 4.259

Further Electronic Structure Discussion.

The ground and low-lying excited states in AmBr3(OPcy3)3 were calculated to gain a

better understanding what role the ligands play in bonding to americium. For comparison, the

same calculations were performed on the cerium and neodymium complexes to determine the

ground state multiplet splitting. The ground multiplet splitting in CeBr3(OPcy3)3 corresponds

to an unusual J = 5/2 for a Ce(III) complex, and is reflected in the spitting of the low-lying

Kramer's doublets (KDs) at 831.5 cm−1

. The closest reported value is 1036.6 cm−1

for

{(C8H6(SiMe3)2]2Ce}−.1 A simple calculation of the free-Ce(III) ion shows a splitting of 2

cm−1

, which highlights the role of the phosphine oxide ligand.. When the same analysis is

performed on NdBr3(OPcy3)3 a ground state J = 9/2 multiplet that spans an energy window of

413.8 cm−1

is calculated and is comparable to the ~495 cm−1

experimentally determined value

for Nd2O3 crystals.2 Unfortunately, this analysis cannot be performed for AmBr3(OPcy3)3

because there is no splitting due to the J = 0 ground state. However, it is clear that the quasi-

octahedral environment provides a strong ligand field environment capable of modifying the

electronic properties of these complexes.

S20

ITI COMPARISONS AND CALCULATIONS OF LITERATURE COMPOUNDS

Table S6. ITI Calculations of Newly Reported and Previously Reported LnBr3(OPcy3)3

Compounds.a

Lab La

3 Ce

b Pr

b Pr

3 Nd

b Nd

3 Gd

3 Ho

3

Radiusc 1.032 1.032 1.01 0.99 0.99 0.983 0.983 0.938 0.901

ITIM–Br 99.1(1) 99.7(1) 99.0(2) 98.9(2) 98.7(5) 98.9(2) 98.7(3) 98.7(3) 98.7(3)

ITIM–O 99.0(3) 99.0(3) 98.56(8) 98.4(2) 98.3(2) 98.6(3) 98.7(2) 99.0(1) 98.5(3)

aGiven with calculated standard error in parentheses

bThis work

c6-Coordinate Shannon Ionic

Radius

Table S7. ITI Calculations of LnI3(Et2O)3 Compounds.4,a,b

Ce Pr Nd Sm Gd Tb

Radius 1.01 0.99 0.983 0.958 0.938 0.923

ITIM–I 101.21(2) 101.22(2) 99.87[7] 101.16(2) 100.96(2) 101.00(2)

ITIM–O 95.8(1) 95.4(2) 97.6[7] 95.1(2) 96.1(1) 95.9(2)

aGiven with calculated standard errors in parentheses and propagated error in square brackets

b6-Coordinate Shannon Ionic Radius

5

Table S8. ITI Calculations of LnCl3(HMPA)3 Compounds.a,b

Pr6 Dy

7 Yb

8

Radius 0.99 0.912 0.868

ITIM–Cl 100.8(1) 100.4(1) 100.3(1)

ITIM–O 100.1(1) 98.92(2) 100.3(1)

aGiven with calculated standard errors in parentheses


5

Table S9. ITI Calculations of YbX3(THF)3 Compounds.a,b

Cl9 Br

10 I

11

ITIM–X 100.7(1) 101.6[1] 101.34[2]

ITIM–O 96.9(5) 96.8[5] 97.3[3]

aGiven with calculated standard errors in parentheses and propagated error in square brackets


5

S21

CRYSTALLOGRAPHY

Table S10. Summary of Crystallographic Collections for MBr3(OPcy3)3.

Compound Am La Ce Pr Nd

Empirical

Formula

C54H99O3P3

Br3Am

C54H99O3P3

Br3La

C54H99O3P3

Br3Ce

C54H99O3.5P3

Br3Pr

C54H99O3P3

Br3Nd

Temperature

(K) 120(2) 130(2) 120(2) 120(2) 120(2)

Crystal

System Orthorhombic Orthorhombic Orthorhombic Orthorhombic Orthorhombic

Space Group Pca21 Pca21 Pca21 Pca21 Pca21

a (Å) 28.768(9) 28.879(2) 28.920(5) 28.716(1) 28.706(1)

b (Å) 11.456(4) 11.4223(7) 11.434(2) 11.4126(4) 11.4228(4)

c (Å) 18.185(6) 18.208(1) 18.209(3) 18.1299(8) 18.1359(7)

(°) 90 90 90 90 90

(°) 90 90 90 90 90

(°) 90 90 90 90 90

Volume (Å3) 5993(3) 6006.3(6) 6021(2) 5941.5(4) 5946.8(4)

Z 4 4 4 4 4

calcd

(Mg/m3)

1.521 1.402 1.400 1.420 1.422

(mm−1

) 3.398 2.824 2.864 2.956 3.007

R1a

(I > 2.0 0.0399 0.0348 0.0353 0.0317 0.0405

wR2

(all data) 0.0858 0.0620 0.0726 0.0617 0.0777

BASF 0.02978 0.01767 0.03608 0.00891 -0.00554

aDefinitions: wR2 = {[w(Fo

2−Fc

2)2] / [w(Fo

2)2]}

1/2 R1 = ||Fo|−|Fc|| / |Fo|

Goof = S = {[w(Fo2−Fc

2)2] / (n−p)}

1/2 where n is the number of reflections and p is the total

number of parameters refined.

S22

Table S11. Bond lengths [Å] and angles [°] for AmBr3(OPcy3)3.

_____________________________________________________

Am(1)-Br(1) 2.882(1)

Am(1)-Br(2) 2.870(1)

Am(1)-Br(3) 2.912(1)

Am(1)-O(1) 2.312(7)

Am(1)-O(2) 2.302(7)

Am(1)-O(3) 2.349(6)

Br(1)-Am(1)-Br(3) 95.60(5)

Br(2)-Am(1)-Br(1) 172.74(3)

Br(2)-Am(1)-Br(3) 91.54(5)

O(1)-Am(1)-Br(1) 89.05(18)

O(1)-Am(1)-Br(2) 89.73(19)

O(1)-Am(1)-Br(3) 89.44(18)

O(1)-Am(1)-O(3) 90.2(3)

O(2)-Am(1)-Br(1) 90.44(18)

O(2)-Am(1)-Br(2) 91.00(18)

O(2)-Am(1)-Br(3) 88.81(18)

O(2)-Am(1)-O(1) 178.1(2)

O(2)-Am(1)-O(3) 91.6(3)

O(3)-Am(1)-Br(1) 87.6(2)

O(3)-Am(1)-Br(2) 85.2(2)

O(3)-Am(1)-Br(3) 176.7(2)

_____________________________________________________________

Table S12. Bond lengths [Å] and angles [°] for LaBr3(OPcy3)3.

_____________________________________________________

La(1)-Br(1) 2.9365(7)

La(1)-Br(2) 2.9425(7)

La(1)-Br(3) 2.9649(5)

La(1)-O(1) 2.351(4)

La(1)-O(2) 2.363(4)

La(1)-O(3) 2.382(3)

Br(1)-La(1)-Br(2) 172.59(2)

Br(1)-La(1)-Br(3) 91.39(3)

Br(2)-La(1)-Br(3) 95.84(3)

O(1)-La(1)-Br(1) 91.08(10)

O(1)-La(1)-Br(2) 90.73(10)

O(1)-La(1)-Br(3) 88.27(9)

O(1)-La(1)-O(2) 178.16(13)

O(1)-La(1)-O(3) 91.97(14)

O(2)-La(1)-Br(1) 89.62(10)

O(2)-La(1)-Br(2) 88.79(10)

O(2)-La(1)-Br(3) 90.01(10)

O(2)-La(1)-O(3) 89.78(15)

O(3)-La(1)-Br(1) 85.23(12)

O(3)-La(1)-Br(2) 87.53(12)

O(3)-La(1)-Br(3) 176.61(12)

_____________________________________________________________

Table S13. Bond lengths [Å] and angles [°] for CeBr3(OPcy3)3.

_____________________________________________________

Ce(1)-Br(1) 2.9268(8)

Ce(1)-Br(2) 2.9166(8)

Ce(1)-Br(3) 2.9504(8)

Ce(1)-O(1) 2.332(4)

Ce(1)-O(2) 2.336(4)

Ce(1)-O(3) 2.368(4)

Br(1)-Ce(1)-Br(3) 95.47(3)

Br(2)-Ce(1)-Br(1) 172.78(2)

Br(2)-Ce(1)-Br(3) 91.61(3)

O(1)-Ce(1)-Br(1) 90.50(10)

O(1)-Ce(1)-Br(2) 91.16(10)

S23

O(1)-Ce(1)-Br(3) 88.33(11)

O(1)-Ce(1)-O(2) 177.66(14)

O(1)-Ce(1)-O(3) 92.37(16)

O(2)-Ce(1)-Br(1) 89.08(11)

O(2)-Ce(1)-Br(2) 89.55(11)

O(2)-Ce(1)-Br(3) 89.42(11)

O(2)-Ce(1)-O(3) 89.91(16)

O(3)-Ce(1)-Br(1) 87.42(13)

O(3)-Ce(1)-Br(2) 85.48(13)

O(3)-Ce(1)-Br(3) 177.02(12)

_____________________________________________________________

Table S14. Bond lengths [Å] and angles [°] for PrBr3(OPcy3)3.

_____________________________________________________

Pr(1)-Br(1) 2.8781(7)

Pr(1)-Br(2) 2.8894(7)

Pr(1)-Br(3) 2.9145(5)

Pr(1)-O(1) 2.294(4)

Pr(1)-O(2) 2.302(4)

Pr(1)-O(3) 2.336(3)

Br(1)-Pr(1)-Br(2) 173.18(2)

Br(1)-Pr(1)-Br(3) 91.37(3)

Br(2)-Pr(1)-Br(3) 95.32(2)

O(1)-Pr(1)-Br(1) 90.95(10)

O(1)-Pr(1)-Br(2) 90.53(10)

O(1)-Pr(1)-Br(3) 88.55(10)

O(1)-Pr(1)-O(2) 177.63(13)

O(1)-Pr(1)-O(3) 92.17(15)

O(2)-Pr(1)-Br(1) 89.61(10)

O(2)-Pr(1)-Br(2) 89.18(10)

O(2)-Pr(1)-Br(3) 89.13(10)

O(2)-Pr(1)-O(3) 90.17(15)

O(3)-Pr(1)-Br(1) 85.72(12)

O(3)-Pr(1)-Br(2) 87.57(12)

O(3)-Pr(1)-Br(3) 177.02(11)

_____________________________________________________________

Table S15. Bond lengths [Å] and angles [°] for NdBr3(OPcy3)3.

_____________________________________________________

Nd(1)-Br(1) 2.8796(8)

Nd(1)-Br(2) 2.8908(9)

Nd(1)-Br(3) 2.9168(6)

Nd(1)-O(1) 2.297(5)

Nd(1)-O(2) 2.309(5)

Nd(1)-O(3) 2.336(4)

Br(1)-Nd(1)-Br(2) 173.15(3)

Br(1)-Nd(1)-Br(3) 91.38(3)

Br(2)-Nd(1)-Br(3) 95.34(3)

O(1)-Nd(1)-Br(1) 91.04(13)

O(1)-Nd(1)-Br(2) 90.45(13)

O(1)-Nd(1)-Br(3) 88.59(12)

O(1)-Nd(1)-O(2) 177.70(16)

O(1)-Nd(1)-O(3) 92.20(19)

O(2)-Nd(1)-Br(1) 89.81(14)

O(2)-Nd(1)-Br(2) 88.95(13)

O(2)-Nd(1)-Br(3) 89.26(13)

O(2)-Nd(1)-O(3) 89.99(19)

O(3)-Nd(1)-Br(1) 85.78(15)

O(3)-Nd(1)-Br(2) 87.49(15)

O(3)-Nd(1)-Br(3) 177.06(14)

_____________________________________________________________

S24

X-ray Data Collection, Structure Solution and Refinement for AmBr3(OPcy3)3.

An amber crystal of approximate dimensions 0.06 x 0.12 x 0.196 mm was mounted

on a nylon loop and transferred to a Bruker D8 Quest diffractometer. The APEX312

program

package was used to determine the unit-cell parameters and for data collection (17 sec/frame

scan time for a calculated scan of diffraction data and a detector distance of 41 mm). The raw


and SADABS14


Subsequent calculations were carried out using the SHELXTL15

or OLEX216

program. The

diffraction symmetry was mmm and the systematic absences were consistent with the

orthorhombic space groups Pbcm and Pca21. It was later determined that space group Pca21

was correct.

The initial structure was solved by direct methods using Pu in place of Am, since Am

is not recognized by APEX3. The structure was refined on F2 by full-matrix least-squares

techniques using Am, the scattering factors for which were taken from the International

Tables for Crystallography Volume C.17

The analytical scattering factors for neutral atoms

were used throughout the analysis.17

Hydrogen atoms were included using a riding model.

The absolute structure was assigned by refinement of the Flack parameter.18

Based on

the Flack parameter, the data was refined as a 2-component twin with BASF = 0.02978. The

compound was found to isomorphous with its lanthanide analogs: Pr (BUGRIG),3 Nd

(BUGROM),3 Gd (BUGRUS),

3 Ho

(ROVNUN),3 which are all

reported as a hemi-hydrate, which

was not located in the Fourier map

for Am.

Figure S15. Thermal ellipsoid plot of AmBr3(OPcy3)3 drawn at the 50% probability level

with hydrogen atoms omitted for clarity.

Am1 O1 O2

O3

P1 P2

P3

Br1

Br2

Br3

S25

Table S16. Crystal data and structure refinement for AmBr3(OPcy3)3.

Identification code cjw84 (Cory Windorff)

Empirical formula C54H99O3P3Br3Am

Formula weight 1371.97

Temperature 120(2) K

Wavelength 0.71073 Å

Crystal system Orthorhombic

Space group Pca21

Unit cell dimensions a = 28.768(9) Å = 90°.

b = 11.456(4) Å = 90°.

c = 18.185(6) Å = 90°.

Volume 5993(3) Å3

Z 4

Density (calculated) 1.521 Mg/m3

Absorption coefficient 3.398 mm−1

F(000) 2768

Crystal color clear yellow

Crystal size 0.196 x 0.12 x 0.06 mm3

Theta range for data collection 2.217 to 27.521°

Index ranges −35 ≤ h ≤ 37, −14 ≤ k ≤ 14, −23 ≤ l ≤ 20

Reflections collected 70455

Independent reflections 12088 [R(int) = 0.0751]

Completeness to theta = 25.242° 99.9 %

Absorption correction Semi–empirical from equivalents

Max. and min. transmission 0.0949 and 0.0640

Refinement method Full–matrix least–squares on F2

Data / restraints / parameters 12088 / 1 / 578

Goodness-of-fit on F2 1.081

Final R indices [I>2sigma(I) = 9606 data] R1 = 0.0399, wR2 = 0.0787

R indices (all data, 0.77 Å) R1 = 0.0606, wR2 = 0.0858

Absolute structure parameter 0.004(7)

Largest diff. peak and hole 2.033 and −2.008 e.Å−3

BASF 0.02978

S26

X-ray Data Collection, Structure Solution and Refinement for LaBr3(OPcy3)3.

A colorless crystal of approximate dimensions 0.153 x 0.157 x 0.267mm was

mounted on a nylon loop and transferred to a Bruker D8 Quest diffractometer. The APEX312

program package was used to determine the unit-cell parameters and for data collection (15

sec/frame scan time for a calculated scan of diffraction data and a detector distance of 33

mm). The raw frame data was processed using SAINT13

and SADABS14

to yield the

reflection data file. Subsequent calculations were carried out using the SHELXTL15

or

OLEX216

program. The diffraction symmetry was mmm and the systematic absences were

consistent with the orthorhombic space groups Pbcm and Pca21. It was later determined that

space group Pca21 was correct.

The structure was solved by direct methods and refined on F2 by full-matrix least-

squares techniques. The analytical scattering factors for neutral atoms were used throughout

the analysis.17



Based on


compound was not isomorphous with its previous report (BUGREC),3 and was found to

isomorphous with its other lanthanide analogs: Pr (BUGRIG),3 Nd (BUGROM),

3 Gd

(BUGRUS),3 and Ho (ROVNUN),

3 which are all reported as a hemi-hydrate, which was not

located in the Fourier map for La.

Figure S16. Thermal ellipsoid plot of LaBr3(OPcy3)3 drawn at the 50% probability level


La1 O1 O2

O3

P1 P2

P3

Br1

Br2

Br3

S27

Table S17. Crystal data and structure refinement for LaBr3(OPcy3)3.


Empirical formula C54H99O3P3Br3La





Space group Pca21


b = 11.4223(7) Å = 90°.

c = 18.2083(10) Å = 90°.

Volume 6006.3(6) Å3

Z 4



F(000) 2616

Crystal color clear colorless



Index ranges −37 ≤ h ≤ 37, −14 ≤ k ≤ 14, −22 ≤ l ≤ 23













BASF 0.01767

S28

X-ray Data Collection, Structure Solution and Refinement for CeBr3(OPcy3)3.

An orange crystal of approximate dimensions 0.123 x 0.156 x 0.268 mm was mounted

on a nylon loop and transferred to a Bruker D8 Quest diffractometer. The APEX312

program

package was used to determine the unit-cell parameters and for data collection (60 sec/frame

scan time for a calculated scan of diffraction data and a detector distance of 42 mm). The raw


and SADABS14


Subsequent calculations were carried out using the SHELXTL15

or OLEX216

program. The

diffraction symmetry was mmm and the systematic absences were consistent with the


was correct.



the analysis.17



Based on


compound is isomorphous with its other lanthanide analogs: Pr (BUGRIG),3 Nd


3 and Ho (ROVNUN),

3 which are all reported as a hemi-

hydrate, which was not located in the Fourier map for Ce.

Figure S17. Thermal ellipsoid plot of CeBr3(OPcy3)3 drawn at the 50% probability level


Ce1 O1 O2

O3

P1 P2

P3

Br1

Br2

Br3

S29

Table S18. Crystal data and structure refinement for CeBr3(OPcy3)3.


Empirical formula C54H99O3P3Br3Ce





Space group Pca21


b = 11.434(2) Å = 90°.

c = 18.209(3) Å = 90°.

Volume 6021.2(18) Å3

Z 4



F(000) 2620

Crystal color clear orange



Index ranges −37 ≤ h ≤ 37, −14 ≤ k ≤ 14, −23 ≤ l ≤ 23











Absolute structure parameter −0.001(4)


BASF 0.03608

S30

X-ray Data Collection, Structure Solution and Refinement for PrBr3(OPcy3)3.

A colorless crystal of approximate dimensions 0.315 x 0.205 x 0.188 mm was



sec/frame scan time for a calculated scan of diffraction data at a detector distance of 35 mm).

The raw frame data was processed using SAINT13

and SADABS14

to yield the reflection data

file. Subsequent calculations were carried out using the SHELXTL15

or OLEX216

program.

The diffraction symmetry was mmm and the systematic absences were consistent with the


was correct.



the analysis.17



Based on


compound is a redetermination of the previously data (BUGRIG),3 and is isomorphous with

its other lanthanide analogs: Nd


3

and Ho (ROVNUN).3

Figure S18. Thermal ellipsoid plot of PrBr3(OPcy3)3 drawn at the 50% probability level

with hydrogen atoms (and lattice solvent) omitted for clarity.

Pr1 O1 O2

O3

P1 P2

P3

Br1

Br2

Br3

S31

Table S19. Crystal data and structure refinement for PrBr3(OPcy3)3.


Empirical formula C54H99O3P3Br3Pr





Space group Pca21

Unit cell dimensions a = 28.716(1) Å α = 90°.

b = 11.4126(4) Å β = 90°.

c = 18.1299(8) Å γ = 90°.

Volume 5941.5(4) Å3

Z 4



F(000) 2624




Index ranges −37 ≤ h ≤ 37, −14 ≤ k ≤ 14, −23 ≤ l ≤ 23




Absorption correction Semi-empirical from equivalents


Refinement method Full-matrix least-squares on F2







BASF 0.00891

S32

X-ray Data Collection, Structure Solution and Refinement for NdBr3(OPcy3)3.

A colorless crystal of approximate dimensions 0.224 x 0.202 x 0.170 mm was



sec/frame scan time for a hemisphere of diffraction data with a scan width of 0.5° and a

detector distance of 35 mm). The raw frame data was processed using SAINT13

and

SADABS14

to yield the reflection data file. Subsequent calculations were carried out using

the SHELXTL15

or OLEX216

program. The diffraction symmetry was mmm and the

systematic absences were consistent with the orthorhombic space groups Pbcm and Pca21. It

was later determined that space group Pca21 was correct.



the analysis.17



Based on

the Flack parameter, the data was refined as a 2-component twin with BASF = -0.00554. The

structure is known (BUGROM)3 and was re-determined. The compound is isomorphous with

its other lanthanide analogs: Pr (BUGRIG),3 Gd (BUGRUS),

3 and Ho (ROVNUN),

3 which

are all reported as a hemi-

hydrate, which was not

located in the Fourier map

for Nd.

Figure S19. Thermal ellipsoid plot of NdBr3(OPcy3)3 drawn at the 50% probability level


Nd1 O1 O2

O3

P1 P2

P3

Br1

Br2

Br3

S33

Table S20. Crystal data and structure refinement for NdBr3(OPcy3)3.


Empirical formula C54H99O3P3Br3Nd





Space group Pca21


b = 11.4137(6) Å = 90°.

c = 18.1291(10) Å = 90°.

Volume 5946.8(4) Å3

Z 4



F(000) 2628




Index ranges −37 ≤ h ≤ 37, −14 ≤ k ≤ 14, −22 ≤ l ≤ 23




Absorption correction Semi-empirical from equivalents


Refinement method Full-matrix least-squares on F2





Absolute structure parameter -0.006(12)


BASF -0.00554

S34

REFERENCES

1. Singh, S. K.; Gupta, T.; Ungur, L.; Rajaraman, G., Chem. Eur. J. 2015, 21, 13812-

13819.

2. Mann, M. M.; DeShazer, L. G., J. Appl. Phys. 1970, 41, 2951-2957.

3. Bowden, A.; Lees, A. M. J.; Platt, A. W. G., Polyhedron 2015, 91, 110-119.

4. Gompa, T. P.; Rice, N. T.; Russo, D. R.; Aguirre Quintana, L. M.; Yik, B. J.; Bacsa, J.;

La Pierre, H. S., Dalton Trans. 2019, 48, 8030-8033.

5. Shannon, R., Acta Cryst. 1976, A32, 751-767.

6. Radonovich, L. J.; Glick, M. D., J. Inorg. Nucl. Chem. 1973, 35, 2745-2752.

7. Zhang, X.-W.; Li, X.-F.; Benetollo, F.; Bombieri, G., Inorg. Chim. Acta 1987, 139,

103-104.

8. Hou, Z.; Kobayashi, K.; Yamazaki, H., Chem. Lett. 1991, 20, 265-268.

9. Deacon, G. B.; Feng, T.; Junk, P. C.; Skelton, B. W.; Sobolev, A. N.; White, A. H.,

Aust. J. Chem. 1998, 51, 75-89.

10. Deacon, G. B.; Feng, T.; Junk, P. C.; Meyer, G.; Scott, N. M.; Skelton, B. W.; White,

A. H., Aust. J. Chem. 2000, 53, 853 - 865.

11. Emge, T. J.; Kornienko, A.; Brennan, J. G., Acta Cryst. 2009, C65, m422-m425.

12. APEX3, 2017.3-0; Bruker AXS, Inc.: Madison, WI, 2017.

13. SAINT, 8.34a; Bruker AXS, Inc: Madison, WI, 2013.

14. Sheldrick, G. M. SADABS, 2012/1; Bruker AXS, Inc: Madison, WI, 2012.

15. Sheldrick, G. M. SHELXTL, Bruker AXS, Inc: Madison, WI, 2012.

16. Olex2, 1.2.10; OlexSys Ltd: 2004-2018.

17. Prince, E., 1st online ed.; International Union of Crystallography: 2006; Vol. C:

Mathematical, Physical and Chemical Tables.

18. Flack, H., Acta Cryst. 1983, A39, 876-881.

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