SUPPLEMENTARY INFORMATION€¦ · Synthesis of 3a ..... 12 Conversion of 3a into 2a by treatment with R3

NATURE CHEMISTRY | www.nature.com/naturechemistry 1

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NCHEM.1270

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Supplementary Information Strongly-coupled, binuclear uranium oxo complexes from uranyl oxo-rearrangement and reductive silylationPolly L. Arnold,1* Guy M. Jones,1 Samuel O. Odoh,2 Georg Schreckenbach,2 Nicola Magnani,3,4

and Jason B. Love1*

Contents General Experimental Details ............................................................................................................................................. 1

1H NMR spectrum of [UO2(py)(H2L)], 1, synthesised using literature methods .......................................................... 3 Synthesis of [UO2{N(SiMe3)2}2(py)2] ............................................................................................................................ 3 Synthesis of [UO2{N(SiMe2Ph)2}2(py)2] ........................................................................................................................ 4 Compound 2 ............................................................................................................................................................... 6 Synthesis of [(Me3SiOUO)2(L)] 2a ................................................................................................................................ 6 Synthesis of [(PhMe2SiOUO)2(L)] 2b ........................................................................................................................... 9 Control reactions in the synthesis of 2 ..................................................................................................................... 10 Synthesis of [(PhMe2SiOUO)2(L)] 2b in the presence of N(SiMe3)3 ........................................................................... 10 Synthesis of [(PhMe2SiOUO)2(L)] 2b in the dark ....................................................................................................... 10 Lack of reactivity of [(Me3SiOUO)2(L)] 2a towards silyl group exchange .................................................................. 11 Lack of reactivity of [(Me3SiOUO)2(L)] 2a towards silyl/uranyl group exchange with [UO2{N(SiMe3)2}2(py)2] ......... 11 Optimised synthesis of [(Me3SiOUO)2(L)] 2a ............................................................................................................ 11 Compound 3 ............................................................................................................................................................. 12 Synthesis of 3a .......................................................................................................................................................... 12 Conversion of 3a into 2a by treatment with R3SiCl ................................................................................................... 16 Reactions of [(Me3SiOUO)2(L)] 2a and 3a with oxidants ........................................................................................... 19 Suggested mechanism for the formation of 2 .......................................................................................................... 20

SQUID magnetometry ...................................................................................................................................................... 21 Crystallographic details .................................................................................................................................................... 24

Solid state structure of [UO2{N(SiMe2Ph)2}2(py)2] .................................................................................................... 25 Solid state structure of [(PhMe2SiOUO)2(L)] 2b ........................................................................................................ 25 Solid state structure of [{(Me3SiOUO)(UO2)(L)}UO2(thf)2(μ‐OH)2]2 4 ........................................................................ 26

Computational details ....................................................................................................................................................... 27 References ........................................................................................................................................................................ 35

General Experimental Details All manipulations were carried out under a dry, oxygen-free dinitrogen atmosphere using standard Schlenk techniques

or in an MBraun Labstar glovebox unless otherwise stated. Pyridine was distilled from potassium under dinitrogen and

stored over molecular sieves prior to use. Other solvents were degassed and dried using a Vacuum Atmospheres solvent

system prior to use. Deuterated solvents were boiled over potassium, vacuum transferred, and freeze-pump-thaw

degassed three times prior to use unless otherwise stated. H4L1, [UO2(THF)2{N(SiMe3)2}2]2, [UO2Cl2(THF)2]3,

[KN(SiMe3)2]4, [KN(SiMe2Ph)2]4, and [UO2(py)2(H2L)] (1)5 were synthesised according to literature procedures. I2 was

sublimed at 80ºC / 10-4 mbar; TMSCl and chlorodiphenylsilane was distilled from magnesium turnings, and TMSOTf

was dried over activated sieves before use. [FeCp2]OTf was prepared via addition of ferrocene to a solution of silver

trifluoromethanesulfonate in CH2Cl2 followed by recrystallisation from a CH2Cl2/THF mixture at -35ºC. All other

reagents were used as purchased. Elemental analyses were carried out by Analytische Laboratorien, Lindlar, Germany. 1H and 29Si NMR spectra were recorded on a Bruker AVA400 spectrometer operating at 399.90 and 79.4 MHz

respectively. 13C{1H} NMR spectra were recorded on a Bruker AVA500 operating at 125.76 MHz. Chemical shifts are

reported in parts per million and referenced to residual proton resonances calibrated against external TMS. All spectra

Strongly coupled binuclear uranium–oxo complexes from uranyl oxo rearrangement and reductive silylation Strongly coupled binuclear uranium–oxo complexes from uranyl oxo rearrangement and reductive silylation

© 2012 Macmillan Publishers Limited. All rights reserved.



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were recorded at 298 K. Infrared spectra were recorded on a Jasco 410 spectrophotometer, w = weak, m = medium, s =

strong intensity. Cyclic voltammetry experiments were performed using an Autolab 302 potentiostat and the data

processed using GPES Manager version 4.9. Experiments were performed in a glovebox using a 15 mL glass vial as the

cell. The working electrode consisted of a platinum wire embedded in glass, the counter electrode a platinum wire and

the reference electrode silver wire. The solution employed was 1.0 mM [(Me3SiOUO)2(L)] 2a and 0.2 M [Bu4N][BF4]

with scan rates 100-1000 mVs-1. All potentials are reported versus [Cp2Fe]0/+. Variable temperature magnetic

susceptibilities were measured using a Quantum Design MPMS-XL SQUID susceptometer operating at 10000 or 50000

Oe in the temperature range 2 to 300 K. The sample was loaded in a gelatine capsule in a dinitrogen-filled glovebox and

suspended in a plastic straw. Diamagnetic contributions from the ligands were calculated using Pascal’s constants.

Abbreviations and compound numbering and lettering scheme

py = pyridine THF = tetrahydrofuran DCM = dichloromethane TMS = trimethylsilyl OTf = trifluoromethanesulfonate, triflate




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Synthesis and Characterisation

1H NMR spectrum of [UO2(py)(H2L)], 1, synthesised using literature methods

Fig SI.1: 1H NMR spectrum of [UO2(py)(H2L)] 1 in d5-pyridine (*)

Synthesis of [UO2{N(SiMe3)2}2(py)2] Method A

[UO2{N(SiMe3)2}2(THF)2] (1.79 g, 2.44 mmol) was dissolved in pyridine (5 mL) and stored at -35 ºC. Orange crystals

of [UO2{N(SiMe3)2}2(py)2] appeared after 24 h and were isolated by filtration, washed with hexane (3 x 2 mL) and

dried under reduced pressure for one hour. The product was isolated as an orange solid. (1.32 g from successive

crystallisations, 1.76 mmol, 73 %). 1H NMR (pyridine-d5): δH 0.30 (br.s, 36H, methyl) 1H NMR (C6D6): 9.31 (m, 8H, pyridine), 6.91 (m, 4H, pyridine),

6.78 (m, 8H, pyridine), 0.62 (br.s, 18H, methyl), 0.46 (br.s, 54H, methyl). 13C{1H} NMR (C6D6): δC 151.48 (pyridine), 139.25 (pyridine), 125.05 (pyridine), 7.46 (methyl), 7.21 (methyl).

FTIR (nujol, cm-1): 1637 (m), 1600 (m), 1255 (m), 1238 (m), 1224 (m), 1155 (w), 1070 (w), 1037 (w), 1010 (m), 935

(m), 887 (m), 775 (w), 755 (w).

Method B

To a suspension of [UO2Cl2(THF)2] (7.00 g, 14.5 mmol) in pyridine (10 mL) was added a solution of [KN(SiMe3)2]

(5.78 g 29.0 mmol) (10 ml) and the mixture stirred for 3 h during which the colour changed from yellow to red. The

volatiles were then removed in vacuo and the resultant red residue dried under vacuum for 12 h. Benzene (20 mL) was

then added, forming an orange solution and an off-white solid. The mixture was then filtered through a Celite pad

before being concentrated under reduced pressure. Orange crystals of [UO2{N(SiMe3)2}2(py)2] appeared at room

temperature after 24 h and were isolated by filtration, washed with hexane (3 x 5 mL) and dried under reduced pressure

for one hour. The product was collected as an orange, crystalline solid (6.62 g from successive crystallisations, 8.85

mmol, 61 %).

*

*

*




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Fig SI.3: FTIR spectrum of [UO2{N(SiMe3)2}2(py)2] (Nujol mull)

Synthesis of [UO2{N(SiMe2Ph)2}2(py)2] To a suspension of [UO2Cl2(THF)2] (2.00 g, 4.14 mmol) in pyridine (5 mL) was added a solution of [KN(SiMe2Ph)2]

(2.68 g, 8.28 mmol) (2 mL) and the resulting orange solution stirred for 3 h after which the volatiles were removed

under reduced pressure and the resulting yellow oil dried under vacuum for 12 h. The product was then extracted into

boiling hexanes (10 x 10 mL), filtered through a Celite pad and the resulting orange solution allowed to cool to room

temperature resulting in the precipitation of yellow crystals after 12 h. [UO2{N(SiMe2Ph)2}2(py)2] was isolated by

filtration as a yellow solid (2.89 g, 2.90 mmol, 70 %). 1H NMR (C6D6): δH 8.52 (m, 4H, pyridine), 7.50 (d, 8H, aryl), 7.12 (m, 12H, aryl) 6.95 (t, 2H, pyridine), 6.72 (m, 4H,

pyridine), 0.54 (s, 24H, methyl). 13C{1H} NMR (C6D6) δC 151.76 (pyridine), 147.18 (quaternary, aryl) 138.65 (pyridine)

*

Fig. SI.2: 1H NMR spectrum of [UO2{N(SiMe3)2}2(py)2] in C6D6 (* = residual C6D5H)




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134.62 (aryl), 128.35 (aryl), 127.43 (aryl), 124.88 (pyridine), 6.89 (methyl). Uranium Analysis, Found: 25.1 %.

C42H54N4O2Si4U requires 23.9 %.

FTIR (nujol, cm-1): 1600 (w), 1247 (m), 1238 (w), 1222 (m) 1182 (m), 1155 (m), 1106 (m), 1066 (w), 1039 (w),

1004(w), 950 (s), 923 (w), 833 (m) , 800 (w).

Fig. SI.4: 1H NMR Spectrum of [UO2{N(SiMe2Ph)2}2(py)2] in C6D6 (* = residual C6D5H, a = hexane, b = residual HN(SiMe2Ph)2)

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Fig SI.5: FTIR spectrum of [UO2{N(SiMe2Ph)2}2(py)2] (Nujol mull)

b

*

a

a

b

b




SI 6

Compound 2

Synthesis of [(Me3SiOUO)2(L)] 2a Method A, from H4L

To a solution of H4L (441 mg, 0.668 mmol) in pyridine (2 mL) was added a solution of [UO2{N(SiMe3)2}2(py)2] (1.249

g, 1.67 mmol, 2.5 equiv) in pyridine (2 mL) and the resulting brown solution heated at 120 ºC in a Teflon-tapped

ampoule for 12 h. The volatiles were removed under reduced pressure and the resulting brown solids dried under

vacuum for 12 h. Extraction into hot hexanes (5 x 5 mL) afforded a brown mixture which was filtered and the filtrate

concentrated to 5 mL and cooled to -35 °C. The brown, hexane-insoluble material remaining after extraction was dried

for 3 h under vacuum and stored in the glovebox (3a and a small amount of intractable material, yield 490 mg). After

storage of the filtrate for 24 h, brown crystalline [(Me3SiOUO)2L] 2a formed and was isolated by filtration and dried

under vacuum for 30 min. Yield 332 mg, 0.247 mmol, 37 %. Crystals of 2a suitable for single crystal X-ray diffraction

were grown at -35°C from a saturated toluene solution.

Method B, from [UO2(py)(H2L)] 1

To a solution of [UO2(py)(H2L)] 1 (285 mg, 0.283 mmol) in pyridine (2 mL) was added a solution of

[UO2{N(SiMe3)2}2(py)2] (318 mg 0.424 mmol, 1.5 equiv) in pyridine (2 mL) and the resulting brown solution heated at

120 ºC in a sealed ampoule for 12 h. The volatiles were removed under reduced pressure and the resulting brown solids

dried under vacuum for 12 h. The product was then extracted into hot hexanes (5 x 2 mL) leaving the brown solid which

comprises 3a and a small amount of intractable material (190 mg), and the brown filtrate which was reduced in volume

to 2 mL before being placed at -35 °C. Brown crystals of the product formed from the filtrate after 24 h and the product

was isolated by filtration and dried under vacuum for 30 min. [(Me3SiOUO)2(L)] 2a was isolated as a brown solid (95

mg, 0.071 mmol, 25 %).

Air/moisture stability test: 2a (10 mg, 0.007 mmol) and 1,3,5-tri-tert-butylbenzene (2 mg, 0.007 mmol) was dissolved

in wet C6D6 (0.5 mL, used as purchased) in air. Neither precipitation nor decomposition was observed after 48 h,

visually, and by 1H NMR spectroscopy. 20 % decomposition to H4L was seen after 5 days by 1H NMR spectroscopy.

Characterisation data for 2a: 1H NMR (C6D6): δH 14.81 (s, 18H, SiMe3), 13.21 (d, 4H, pyrrole), 8.90 (d, 4H, pyrrole),

7.73 (s, 4H, imine), 4.38 (s, 6H, meso-methyl), -3.15 (s, 12H, aryl-methyl), -3.78 (s, 4H, aryl), -11.08 (s, 6H, meso-

methyl). 29Si NMR (C6D6): δSi 160.1.

Analysis. Found: C, 42.83; H, 4.23; N, 8.39. C42H54N4O2Si4U requires: C, 42.92; H, 4.35; N, 8.34 %.

IR (Nujol mull, cm-1): (L = stretches assigned to ligand) ν 1594 (s, L), 1575 (s, L), 1284 (s, L), 1269 (m, Si-CH3), 1100

(m, Si-O), 1049 (s, L), 1018 (m, L), 906 (w, L), 862 (m, U-O), 802 (m, U-O) cm-1.

eff (Evans' method): 2.42 μB per molecule.

Cyclic Voltammetry (THF): No oxidation was observed within the limits of the solvent window (-3 to + 1 V vs Fc+/Fc).




SI 7

Fig. SI.6: 1H NMR spectrum of [(Me3SiOUO)2L] 2a in C6D6 (* = residual C6D5H a = toluene, b = grease)

-20

-10

0

10

20

30

40

-3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5E / V vs. Fc+ / Fc

I / μ

A

1mM solution of complex 2, 1000 mV s-1

1mM solution of complex 2 and 1mM ferrocene 1000 mV s-1

Fig SI.7: Cyclic voltammogram of 2a in THF (blue) at 25 oC (vs. ferrocenium/ferrocene (Fc+/Fc), 0.2M NBu4BF4 as supporting electrolyte). The orange line shows the Fc+/Fc at the same molar concentration as 2a.

a b

*




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2a

2b

Fig. SI.8: FTIR spectrum of [(Me3SiOUO)2(L)] 2a and [(PhMe2SiOUO)2(L)] 2b for comparison (Nujol Mull)




SI 9

Synthesis of [(PhMe2SiOUO)2(L)] 2b To a solution of [UO2(py)(H2L)], 1 (93 mg, 0.092 mmol) in pyridine (1.5 mL) was added a solution of

[UO2{N(SiMe2Ph)2}2(py)2] (138 mg 0.139 mmol, 1.5 equivs) in pyridine (1.5 mL) and the resulting brown solution

heated at 120 ºC in a Teflon-tapped ampoule for 12 h. The volatiles were removed under reduced pressure and the

resulting brown solids dried under vacuum for 12 h. The product [(PhMe2SiOUO)2(L)] was then extracted into hot

toluene (5 x 2 mL) leaving the intractable dark solid 3b. The brown filtrate was reduced in volume to 1 mL before being

placed at -35 °C. Microcrystalline solids appeared from the filtrate after 24 h and the product was isolated by filtration

and dried under vacuum for 30 min. [(PhMe2SiOUO)2(L)] 2b was collected as a brown solid (31 mg, 0.021 mmol,

22 %). Crystals of 2b suitable for X-ray diffraction were grown by slow diffusion of hexane into a saturated benzene

solution at room temperature.

Characterisation for 2b: 1H NMR (C6D6): δH 17.35 (s, 12H, SiMe2), 14.67 (d, 4H, J = 7 Hz SiPh), 13.09 (d, 4H, J = 3 Hz,

pyrrole), 8.74 (d, 4H, J = 3 Hz, pyrrole), 8.48 (t, 4H, J = 7 Hz, SiPh), 7.81 (t, 2H, J = 7 Hz, SiPh), 7.58 (s, 4H, imine)

4.30 (s, 6H, meso-methyl), -2.89 (s, 12H, aryl-methyl), -4.00 (s, 4H, aryl), -11.20 (s, 6H, meso-methyl). 29Si NMR

(C6D6): δSi 151.9.

Analysis. Found: C, 49.09; H, 4.58; N, 6.87 %. C58H62N8O4Si2U2.(C6H5CH3)0.6 requires: C, 49.09; H, 4.42; N, 7.35 %. IR (Nujol mull, cm-1): ν 1598 (s, L), 1575 (s, L), 1265 (m, Si-Me), 1114 (m, Si-O), 906 (m, L), 890-850 (s, U-O

stretches).

eff (Evans' method, C6D6): 2.46 B per molecule.

Characterisation for compound 3b isolated from this reaction: 1H NMR (pyridine- d5): virtually silent, FTIR (Nujol mull,

cm-1) ν 1592 (m, L), 1573 (m, L), 1287 (m, L), 1051 (w, L), 1020 (w, L), 914 (w, asymmetric stretch for [UO2]2+.

Fig SI.9: 1H NMR Spectrum of [(PhMe2SiOUO)2(L)] 2b in C6D6 (* = residual C6D5H a = toluene (0.6 eq), b = hexane, c = grease)

-12-11-10-9-8-7-6-5-4-3-2-10123456789101112131415161718ppm

cb

ab

*




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Control reactions in the synthesis of 2

Synthesis of [(PhMe2SiOUO)2(L)] 2b in the presence of N(SiMe3)3 To a solution of [UO2(py)(H2L)] 1 (10 mg, 0.0088 mmol) and N(SiMe3)3 (11 mg, 0.044 mmol) in d5-pyridine was added

a solution of [UO2{N(SiMe2Ph)2}2(py)2] (13 mg 0.013 mmol) in d5-pyridine and the resulting brown solution heated at

120 ºC in an NMR tube. After 12 h, both 1 and [UO2{N(SiMe2Ph)2}2(py)2] were consumed to give a solution of

[(PhMe2SiOUO)2(L)] 2b (0.0026 mmol, 0.3 eq) and HN(SiMe2Ph) (0.018 mmol, 0.7 eq) as observed by 1H NMR

spectroscopy. No consumption of N(SiMe3)3 was observed, which was verified by the subsequent addition of 1eq of tBu3C6H3(2 mg, 0.0088 mmol) as an internal standard.

1H NMR (d5-pyridine): δH 17.23 (s, 12H, SiMe2), 15.57 (d, 4H, J = 7 Hz SiPh), 13.11 (d, 4H, J = 3 Hz, pyrrole), 9.01 (d,

4H, J = 3 Hz, pyrrole), 8.88 (t, 4H, J = 7 Hz, SiPh), 8.39 (s, 4H, imine), 8.15 (t, 2H, J = 7 Hz, SiPh), 7.77 (m,

HN(SiMe2Ph)2), 7.44 (m, HN(SiMe2Ph)2), 4.38 (s, 6H, meso-methyl), -2.72 (s, 12H, aryl-methyl), 0.41 (s,

HN(SiMe2Ph)2), 0.27 (s, N(SiMe3)3) -3.74 (s, 4H, aryl), -10.94 (s, 6H, meso-methyl).

Conclusion: uranyl amide rather than free silylamine is the source of silyl group.

Fig SI:10: 1H NMR Spectrum for synthesis of [(PhMe2SiOUO)2(L)] 2b in the presence of N(SiMe3)3 in d5-pyridine.

Synthesis of [(PhMe2SiOUO)2(L)] 2b in the dark To a solution of H4L (10 mg, 0.015 mmol) in d5-pyridine (0.5 mL) was added a solution of [UO2{N(SiMe2Ph)2}2(py)2]

(38 mg 0.038 mmol) in d5-pyridine (0.5 mL) and the resulting brown solution heated at 120 ºC in an amber NMR tube

for 12 h. [(PhMe2SiOUO)2(L)] 2b and HN(SiMe2Ph) were the only products visible by 1H NMR spectroscopy after the

reaction period.

Conclusion: the reaction does not involve a photochemically-activated uranyl dication.




SI 11

Lack of reactivity of [(Me3SiOUO)2(L)] 2a towards silyl group exchange To a solution of [(Me3SiOUO)2(L)] 2a (10 mg, 0.007 mmol) in C6D6 (1 mL) was added an excess of

chlorodiphenylsilane (drops). No reaction was observed by 1H NMR spectroscopy after 24 h.

Lack of reactivity of [(Me3SiOUO)2(L)] 2a towards silyl/uranyl group exchange with [UO2{N(SiMe3)2}2(py)2] To a solution of [(Me3SiOUO)2(L)] 2a (10 mg, 0.007 mmol) and tBu3C6H3 (2 mg, 0.007 mmol) in d5-pyridine (0.7 mL)

was added an excess of [UO2{N(SiMe3)2}2(py)2] (10mg, 0.013 mmol) and the solution boiled at 120 °C for 12 h. No

reaction or consumption of 2a was observed by 1H NMR spectroscopy.

Optimised synthesis of [(Me3SiOUO)2(L)] 2a To a solution of H4L (740 mg, 1.12 mmol) in pyridine (5 mL) was added a solution of [UO2{N(SiMe3)2}2(py)2] (2.10 g,

2.80 mmol, 2.5 equiv) in pyridine (5 mL) and the resulting brown solution heated at 120 ºC in a Teflon-tapped ampoule

for 12 h during which precipitation of a brown solid of 3a and a small amount of intractable solid, was observed.

Trimethylsilyl chloride (0.7 mL, 5.60 mmol) was then added to the suspension and the solution stirred for 5 min

resulting in the dissolution of all residual solids. The volatiles were then removed under reduced pressure and the

residue dried under vacuum at 70 °C for 2 h. Extraction with hot hexanes (5 x 10 mL) afforded a brown solution with a

small amount of intractable material. The filtrate was decanted off via cannula, concentrated to 10 mL, and cooled to -

35 °C. After storage for 24 h, brown crystalline [(Me3SiOUO)2(L)] 2a, was isolated by filtration and dried under

vacuum for 1 h. Yield .1.10 g, 0.819 mmol, 73 %.




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Compound 3

Synthesis of 3a Method A: From H4L and [UO2{N(SiMe3)2}2(py)2] at 25 ºC

To a solution of H4L (100 mg, 0.151 mmol) in pyridine (1.5 mL) was added a solution of [UO2{N(SiMe3)2}2(py)2] (284

mg, 0.379 mmol, 2.5 equivs) in pyridine (2.5 mL) and the resulting brown solution stirred at room temperature for 14

days after which a brown precipitate formed. The solid was isolated by filtration and dried under vacuum for 2 h at 70

ºC while the filtrate was concentrated under reduced pressure and placed at -35 ºC for 24 h, resulting in the precipitation

of more solids. Compound 3a was isolated as brown solid in a combined yield of 155 mg from multiple batches.

Method B: From H4L and [UO2{N(SiMe3)2}2(py)2] at 70 ºC

The same product can be made more quickly by heating at 70 ºC for four days. The attempted synthesis of 3a at

temperatures above 70 ºC produces quantities of 2a in addition to 3a.

1H NMR in d5-pyridine: Virtually silent at 20 °C and 70 °C. Analysis. Found: C, 39.52; H, 3.37; N, 8.46.

[(HOUO)2(L)(UO2){N(SiMe3)H}(py)] requires C, 39.00; H, 3.45; N, 8.90.

FTIR (Nujol mull, cm-1): 1596 (s, L), 1573 (s, L), 1286 (m, L), 1270 (s), 1043 (s, L), 1018 (m, L), 912 (m, asymmetric

stretch for [UO2]2+), 900 (w), 765 (w), 752 (w), 727 (m), 694 (m), 665 (m)

Solubility: insoluble in pyridine, THF, toluene, benzene, diethyl ether, tert-butanol, and hexane.

Thermal stability: No change in 1H NMR spectrum or solubility upon heating at 90 ºC for several days in d5-pyridine.

Partial decomposition to afford intractable materials occurs upon heating at 120 ºC in d5-pyridine for 24 h although a

very small quantity of 2a is observed to form.

Compound 3b was made similarly from H4L and [UO2{N(SiMe2Ph)2}2(py)2]

Conclusion: Reduction of the uranyl group does not require elevated temperatures.

Synthesis of 3b from H4L and [UO2{N(SiMe2Ph)2}2(py)2]

NMR scale. To a solution of H4L (10 mg, 0.015 mmol) in d5-pyridine (0.3 mL) was added a solution of

[UO2{N(SiMe2Ph)2}2(py)2] (38 mg, 0.038 mmol, 2.5 equivs) and tBu3C6H3 (4mg, 0.015 mmol) in d5-pyridine (0.3 mL)

and the resulting brown solution heated at 70 ºC. After four days a brown precipitate of 3b had formed and only tBu3C6H3 and HN(SiMe2Ph)2 were observed in the 1H NMR spectrum. Addition of trimethylsilyl chloride (drops) to the

reaction resulted in the formation of [(Me3SiOUO)2(L)], 2a as the major product, with a small quantity of mixed

silylated material seen, supporting the prior formation of 3b.

Conclusions: 3 contains only a very small proportion of silylated oxo groups. NMR silent material 3a is not an

intermediate to the thermal formation of 2a or 2b.




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Fig SI.11: 1H NMR spectrum of 3 synthesised from H4L and [UO2{N(SiMe2Ph)2}2(py)2] in d5-pyridine (* = residual C5D4HN, a = tBu3C6H3 and b = HN(SiMe2Ph)2 c = residual [UO2{N(SiMe2Ph)2}2(py)2])

Fig. SI.12: 1H NMR spectrum of the reaction of H4L and 3 equiv. of [UO2{N(SiMe3)2}2(py)2] to form 3a in pyridine, showing the formation of 4 HN(SiMe3)2 and leaving 0.5 equiv. [UO2{N(SiMe3)2}2(py)2] unreacted. C6H3

tBu3 is internal standard.

a

b

a b

c

* ** c c

b




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Fig. SI.13: 1H NMR spectrum of the reaction of H4L with 3 equiv. of [UO2{N(SiMe2Ph)2} 2(py)2] to form 3b in pyridine, showing the formation of 4 HN(SiMe2Ph)2 and leaving 0.5 equiv. [UO2{N(SiMe2Ph)2}2(py)2] unreacted. C6H3

tBu3 is internal standard.

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3 formed as a by product of the high temperature synthesis of 2a

3 formed as a by product of the high temperature synthesis of 2b

Fig. SI.14: FTIR spectra of 3a and 3b made at 120°C during the synthesis of 2a [(Me3SiOUO)2L] or 2b [(PhMe2SiOUO)2L] respectively (Nujol mull)




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LDI Mass spectrometric analysis of 3a Each peak in the spectrum is associated with an envelope of peaks which are related to each other in mass by the loss of an O atom or loss of Me, a common observation in LDI mass spectrometry.

Fig. SI.15: LDI mass spectra of 3a with assignments of primary peaks




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Conversion of 3a into 2a by treatment with R3SiCl Method A: In-situ NMR synthesis of 2a using trimethylsilyl chloride, Me3SiCl.

To a solution of H4L (20 mg, 0.030 mmol) in d5-pyridine (0.3 mL) was added a solution of [UO2{N(SiMe3)2}2(py)2] (57

mg, 0.076 mmol, 2.5 equiv) and tBu3C6H3 (8 mg, 0.030 mmol) in d5-pyridine (0.3 mL) and the resulting brown solution

allowed to stand at room temperature. After 10 days a brown precipitate had formed and only tBu3C6H3 and

HN(SiMe3)2 were observed in the 1H NMR spectrum. The volatiles were removed under reduced pressure and the

brown residue of 3a dried for 2 h at 70 °C before being re-dissolved d5-pyridine. Trimethylsilyl chloride (drops) was

then added resulting in the formation of [(Me3SiOUO)2(L)], 2a in 76 % total yield versus H4L by 1H NMR spectroscopy,

calibrated against tBu3C6H3.

Method B: Bulk scale synthesis of 2a using Me3SiCl

To a slurry of 3a (100 mg, 0.06 mmol based on best estimate of empirical formula) in pyridine (2 mL) was added

trimethylsilyl chloride (0.1 mL) resulting in the complete dissolution of all solids to form a brown solution. The

volatiles were removed under reduced pressure and the resulting residue dried for 2 h at 70 °C. Extraction into hot

hexanes (3 x 2 mL) afforded a small quantity of yellow solid (10 mg)* and a brown filtrate which was concentrated to 2

mL and cooled to -35 °C. After storage for 24 h, brown crystalline [(Me3SiOUO)2(L)] 2a was isolated by filtration and

dried under vacuum for 30 min yielding 2a as a brown solid. Yield 80 mg, 80 % yield based on estimated empirical

formula of 3a.

Note: Samples of 3a formed at temperatures above 70 ºC contain an amount (around 20 % by mass) of intractable

material that is not reactive towards trimethylsilyl chloride or soluble in any common solvent.

*Characterisation data of yellow solid: 1H NMR (5 mg, d5 pyridine): Trace quantities of 2a only. IR bands are attributed

to residual 2a and other undefined material.




SI 17

Fig. SI.16: Upper: 1H NMR spectrum in d5-pyridine of 3a from bulk-scale synthesis B. The three large resonances are pyridine solvent.

Lower: 1H NMR spectrum in d5-pyridine of 2a formed by addition of TMSCl to the tube containing 3a from which the spectrum above was obtained (scale unchanged). The integrations show that HN(SiMe3)2 and 2a are formed in equal amounts. Conversion of 3b (made at 120 oC) to a mixture of [(Me3SiOUO)2(L)] 2a and [(PhMe2SiO)(U2O2)(OSiMe3)(L)]

To an NMR tube containing a suspension of 3b (10 mg) in d5-pyridine was added excess trimethylsilyl chloride (drops)

resulting in the dissolution of some of the solids and the formation of [(Me3SiOUO)2(L)] 2a and the asymmetrically-

silylated compound [(PhMe2SiO)(U2O2)(OSiMe3)(L)] in a 3:1 ratio as evidenced by NMR spectroscopy.

Conclusion: the NMR-silent material formed at 120 ºC reaction comprises mostly 3 but contains a small quantity of

oxo-silylated material with non-labile O-Si bonds.




SI 18

Fig. SI.17: 1H NMR spectrum of reaction B in d5-pyridine with selected areas magnified: a = symmetric bis-silyl compound [(Me3SiOUO)2(L)] 2a; b = resonances attributed to the formation of the asymmetric bis-silyl compound [(PhMe2SiO)(U2O2)(OSiMe3)(L)]

In-situ partial hydrolysis of 3 synthesised at 120 °C to form [(Me3SiO)(U2O3)(L)UO2(-OH)]2 4

A solution of [UO2(py)(H2L)] 1 (211 mg, 0.210 mmol) and [UO2{N(SiMe3)2}2(py)2] (235 mg, 0.315 mmol) in pyridine

(5 mL) was heated at 120 ºC for 12 h resulting in the formation of a brown solution containing 2a and 3a as evidenced

by NMR spectroscopy. The volatiles were removed under reduced pressure and a sample of the crude material exposed

to air resulting in the formation of a new paramagnetic complex, as evidenced by the appearance of broad resonances,

additional to that of 2a, in the 1H NMR spectrum. Single crystals of the dimeric product [(Me3SiO)(U2O3)(L)UO2(-

OH)]2 4 suitable for X-ray diffraction were isolated from a saturated solution of this material in THF.

b

a a

a

a

b b

bb

b

meso-Me

aryl-Me

aryl-H

SiMe3

b b

SiMe2Ph




SI 19

Fig. SI.18: 1H NMR spectrum in d5-pyridine of reaction C: upper = before exposure to air (showing 2a and HN(SiMe3)2), and lower = after exposure to air; a = HN(SiMe3)2, b = resonances attributed to hydrolysis of 3 synthesised at 120 ºC, and possibly attributable to 4.

Reactions of [(Me3SiOUO)2(L)] 2a and 3a with oxidants [Cp2Fe][OTf]: To a solution of [(Me3SiOUO)2(L)] 2a (12.3 mg, 0.009 mmol) in C6D6 (1 mL) was added ferrocenium

trifluoromethanesulfonate (6.1 mg, 0.018 mmol, 2 equiv). No reaction was observed by 1H NMR spectroscopy after one

week.

Ce(OTf)4: To a solution of [(Me3SiOUO)2(L)] 2a (10 mg, 0.007 mmol) in C6D6 (1 mL) was added cerium

tetrakis(trifluoromethanesulfonate) (6.0 mg, 0.018 mmol, 2 equiv). No reaction was observed by 1H NMR spectroscopy

after one week.

Air: A solution of [(Me3SiOUO)2(L)] 2a (10 mg, 0.007 mmol) in C6D6 (1 mL) was exposed to air for 48 h after which

no reaction was observed by 1H NMR spectroscopy.

Iodine: To a solution of [(Me3SiOUO)2(L)] 2a (10 mg, 0.007 mmol) in C6D6 (1 mL) was added iodine (2.0 mg, 0.007

mmol, 1 equiv). No reaction was observed by 1H NMR spectroscopy after 24 h, with partial decomposition to afford

intractable materials occurring after one week.

Conclusion: 2a is remarkably inert to oxidation

Complex 3a also shows no reactivity with [Cp2Fe][OTf] or Ce(OTf)4 under analogous conditions.

Suspensions of 3 in pyridine-d5 showed no evidence of reaction or dissolution in the presence of a variety of Lewis-

bases including DMSO, Ph3P=O, and TMEDA (Me2NCH2CH2NMe2).

b

a

b b b b b

b b b




SI 20

Suggested mechanism for the formation of 2

Fig. SI.19: Suggested mechanism for the formation of 2 showing two competing homolytic bond cleavage processes




SI 21

SQUID magnetometry Solid state magnetic studies were carried out on [(Me3SiOUO)2(L)] 2a (χdia= 4.81 x 10-4 emu mol-1, m = 21.1 mg, Mw =

1343 g mol-1). The temperature dependence between 2 and 300 K of the effective magnetic moment, μeff, and the

inverse susceptibility, 1/χ are shown here; a plot of the magnetic susceptibility, χ, is included in the manuscript.

Magnetic behaviour is independent of the strength of the applied magnetic field (10000 or 50000 Oe) and whether the

sample was field or zero-field cooled.

Fig. SI.20: Temperature-dependent inverse magnetic susceptibility, 1/χ (top), and temperature-dependent effective magnetic moment, μeff (bottom) vs T for 2a in the range 2–300 K measured at 50000 Oe with zero-field cooling. The black line in the top plot is a fit of the high-temperature data to a Curie-Weiss function 1/χ = (T-Θ)/(8μeff

2)




SI 22

The magnetic susceptibility of this uranium dimer was simulated using a spin Hamiltonian of the form

ex21 HHHH containing the Zeeman terms (one for each magnetic site)

)()()(//

yi

xi

ziBi SSgSgBH

and the exchange interaction

)(

2)(

1)(

2)(

1

2

//

)(2

)(1exex

yyxxzz SSSSggSSJH

The influence of the ligand field is taken into account by the anisotropic g factor which acts on the S = ½ pseudo-spin of

the Kramers’ 5f1 electronic configuration. The same anisotropy is reflected on the exchange Hamiltonian: assuming that

the interaction between the real spin moments is isotropic, the spin Hamiltonian for the pseudo-spin states contains both

a Heisenberg-Dirac term and an Ising term. The best fit was obtained with g// = 2.8, g = 0.7, and Jex = -33 cm-1.

While the magnetic coupling due to superexchange is particularly large with respect to other f-electron complexes7, the

antiferromagnetic interaction is not likely to cause the significant reduction of the high-temperature effective magnetic

moment with respect to the value expected for a f 1 ion in LS coupling (2.54 μB/U ion); in fact, this interaction cannot

significantly affect the slope of the linear part of the 1/χ curve, and the effective moment extracted with this method

(1.57 μB/U ion, top panel of Fig. SI.19) is quite close to that obtained from χT at room temperature (1.53 μB/U ion, Fig.

SI.19, bottom). On the other hand, both the effective moment reduction and the obtained g factors are consistent with

the ligand-field model recently proposed for pentavalent monomeric uranyl-type complexes6. Figure SI.20 shows the

calculated g values (top panel) and the calculated effective magnetic moment (bottom panel) as a function of εδ–εφ,

which is the difference in energy between the ml = 2 and the ml = 3 ligand-field orbitals (all other parameters were fixed

to the values given in Ref. 6). The experimental data presented in this work point towards εδ–εφ = –1200 cm-1, close to

the value of –1435 cm-1 obtained in Ref. 6.




SI 23

Figure SI.21: g factors (top) and effective magnetic moment (bottom) for U(V) in uranyl-type complexes, calculated using the model outlined in Ref. 6.




SI 24

Crystallographic details For all structures absorption was corrected for by multi-scan methods, empirical absorption correction used special

harmonics and was implemented in SCALE3 ABSPACK scaling algorithm. H-parameters were constrained to parent

atoms and refined using a riding model. X-ray crystallographic coordinates for [UO2{N(SiMe2Ph)2}2(py)2], 2a, 2b, and

4 have been deposited at the Cambridge Crystallographic Database, numbers CCDC 837886 - 837889.

Table SI.1: Experimental details of crystal data collection for [UO2{N(SiMe2Ph)2}2(py)2], 2a, 2b, and 4

[UO2{N(SiMe2Ph)2}2(py)2] 2a 2b 4

Crystal data

Chemical formula C42H54N4O2Si4U C69H82N8O4Si2U2 C79H83N8O4Si2U2 C65H90N8O12SiU3 Mr 997.28 1619.67 1740.77 1917.63 Crystal system, space group Tetragonal, P4N2 Monoclinic, P21/c Monoclinic, P21/n Triclinic, P-1

Temperature (K) 171 173 171 100 a, b, c (Å) 15.3164 (2), 15.3164 (2),

11.0910 (3) 16.2362 (15), 18.1288 (15), 26.4879 (19)

15.4650 (3), 24.4171 (6), 20.7529 (5)

14.1406 (6), 14.7186 (8), 18.3470 (11)

α, β, γ (°) 90, 90, 90 90, 101.144 (9), 90 90, 101.073 (2), 90 86.724 (5), 77.931 (4), 77.425 (4)

V (Å3) 2601.86 (9) 7649.5 (11) 7690.6 (3) 3644.3 (3)

Z 2 4 4 2 Radiation type Mo Kα Mo Kα Mo Kα Cu Kα µ (mm−1) 3.24 4.31 4.29 19.2

Crystal size (mm) 0.53 × 0.38 × 0.32 0.43 × 0.18 × 0.16 0.38 × 0.25 × 0.21 0.06 × 0.05 × 0.04 Data collection Diffractometer Xcalibur, Eos Xcalibur, Eos Xcalibur, Eos SuperNova, Dual,

Cu at zero, Atlas

Absorption correction Multi-scan Multi-scan Multi-scan Multi-scan Tmin, Tmax 0.281, 0.393 0.988, 0.995 0.767, 0.823 0.671, 1.000

No. of measured, independent and observed [I > 2σ(I)] reflections

15237, 2984, 2418 90284, 17528, 12653

73513, 17617, 12559

?, 7956, 6277

Rint 0.027 0.071 0.061 0.047

θmax (°) 27.5 27.5 27.5 51.8

Refinement R[F2 > 2σ(F2)], wR(F2), S 0.023, 0.066, 1.19 0.054, 0.173, 1.06 0.049, 0.128, 1.12 0.044, 0.105, 1.00

No. of reflections 2984 17528 17617 7956 No. of parameters 126 764 824 796 No. of restraints 0 4 6 6 Δρmax, Δρmin (e Å−3) 0.88, −0.32 3.62, −2.64 3.79, −1.95 1.91, −2.05

Computer programs: CrysalisPro, (Agilent Technologies Ltd., Version 1.171.34.49) SHELXS97 (Sheldrick, 1990),

SIR92 (Giacovazzo, 1994), SHELXL97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 2008), ORTEP (Farrugia, 1997).




SI 25

Solid state structure of [UO2{N(SiMe2Ph)2}2(py)2]

Fig. SI.22: Solid state structure of [UO2{N(SiMe2Ph)2}2(py)2]. For clarity, all hydrogen atoms are omitted. Selected distances (Å) and angles (°): U1-O1 1.782(3), U1-N1 2.346(4), U1-N2 2.531(4), N1-Si1 1.731(2), O1i-U1-O1 180.0, N1-U1-N1ii 180.0, O1-U1-N1 90.0.

Solid state structure of [(PhMe2SiOUO)2(L)] 2b

Fig. SI.23: Solid state structure of [(PhMe2SiOUO)2(L)] 2b. For clarity, all hydrogen atoms and benzene solvent of coordination are omitted. Selected distances (Å) and angles (°): U1-O1 2.030(5), U1-O2 2.081(5), U1-O3 2.081(5), O1-Si1 1.665(5), U1···U2 3.3562(4), Si1-O1-U1 156.1(3), O1-U1-O2 174.4(2), O1-U1-O3 101.6(2), U1-O3-U2 106.54(13), O2-U1-O3 72.82(18).




SI 26

Solid state structure of [{(Me3SiOUO)(UO2)(L)}UO2(thf)2(μ-OH)2]2 4

Fig. SI.24: Molecular structure of [{(Me3SiOUO)(UO2)(L)}UO2(thf)2(μ-OH)2]2 4, a compound isolated from the partial hydrolysis of 3a arising from the reaction between H4L and 2.5 [UO2{N(SiMe3)2}2(py)2] to make 2a at 120 ºC. For clarity, hydrogen atoms except on the hydroxyl oxygen atoms as well as solvent of crystallisation and selected carbon atoms from the macrocyclic framework are omitted (displacement ellipsoids are drawn at 50 % probability). Selected distances (Å) and angles (): U1-O1 1.909(7), U1-O2 2.052(7), U1-O3 2.170(8), U2-O2 2.099(8), U2-O3 2.034(7), U2-O4 2.045(8), Si1-O4 1.666(8), O1-U3 2.312(7), U3-O5 1.757(9), O1-U3 2.312(7), Si1-O4-U2 153.5(5), U1-O2-U2 108.3(3), O1-U1-O2 174.7(3),U1-O1-U3 168.8(4), U3- O7-U3 112.6(4).

The solid state structure of 4 is a symmetrical dimer which can be viewed as a core of hexavalent uranyl hydroxides, capped by two half-silylated U2O4(L) units, in all containing two UVI and four UV dioxo centres. The outer two uranyl units are already in the butterfly conformation and both have metrics consistent with the pentavalent oxidation state. The silylated oxo bond U2-O4 is long at 2.045(8) Å, but still contains multiple bond character, and the exo-oxo O1, which would allow formation of 2a if silylated, has a U1-O1 bond distance of 1.909(7) Å and is also indicative of UV. The butterfly angles are very similar to those in 2a. Atom U1 shows further pentavalent character through its formation of a CCI with U3, whose U-Ooxo distances (1.757(9) and 1.760(8) Å), and lack of oxo basicity are typical for the normal UVI uranyl oxo unit. The CCI is a T-shape through O1, with a near linear U1-O1-U3 angle (174.7(3)º) and a short bond of the O1 oxo donor to hexavalent U3, of O1-U3 2.312(7) Å. This triple-uranium oxo unit forms a dimer through a crystallographic inversion centre between U3 and U3', the two uranyls being chemically joined through a bridging hydroxide group in the equatorial plane. We suggest that these groups arise from the hydrolysis of a uranyl-silylamido group present in 3.




SI 27

Computational details The geometries of 2a in the antiferromagnetic-broken symmetry singlet, restricted singlet, and ferromagnetic triplet states were optimized in the gas phase using DFT calculations. Single point calculations in the pyridine solvent were carried out on the optimized structures by employing the polarisable continuum solvation model in the Kohn-Sham DFT calculations. The uranium atom was described with the Stuttgart relativistic pseudopotential8,9 while all other atoms were described with the 6-31G** basis set. These calculations were performed with the Gaussian 03 suite of programs10. Wiberg bond indices and natural bond orbital analysis were also performed. There is good agreement between the calculations employing pseudopotentials and all-electron basis sets. Scalar relativistic calculations with all-electron basis sets using a four-component approach were also carried out with the Priroda program 11,12. The PBE functional was employed in these calculations while using a triple-ζ (cc-pVTZ) basis set. The small-component portion was described using appropriate kinetically balanced basis sets. The Mayer bond orders were calculated after the geometry optimisation. The U-OSiMe3 stretching vibrations were calculated to be at 826 and 838 cm-1. For the [UO(OSiMe3)H2L] complex in which one oxo atom was silylated, The U-O and U-OSiMe3 stretching modes were calculated to be at 744 and 819 cm-1. Table SI.2: Structural parameters of 2a in the ferromagnetic triplet electronic state and antiferromagnetic broken-symmetry state (in parentheses). Distances are given in Å. B3LYP/RECP Wiberg

Bond Index Mayer- Mulliken Bond Order

PBE/All-electron /4-Component)

Pop. Mayer Bond Orders /All-electron

Expt.

Configuration fαfα (fαfβ) (fαfβ) (fαfβ) fαfα (fαfβ) fαfα (fαfβ) 5-5

Parameters

U-U 3.379 (3.366) 0.140 0.219 3.372 (3.372) 0.34 (0.34) 3.3556(5)

U-Oexo 2.056 (2.053) 0.786 0.991 2.055 (2.050) 1.26 (1.27) 2.041(6)

U-Oendo 2.048, (2.092) 2.048, (2.099) 2.142, (2.093) 2.165 (2.096)

0.794-0.797 0.925-0.950 2.093, (2.076) 2.099, ( 2.099) 2.101, (2.095) 2.105, (2.102)

1.18-1.22 (1.19-1.20)

2.086(5), 2.098(5), 2.094(5), 2.096(5)

U-Oendo-U 107.5 (107.1) 107.1 (107.5) 106.6

U-Ocis-U 106.6 (106.6) 106.6 (106.8) 106.4

U-Nimine 2.539-2.563 (2.538-2.540)

0.267 0.370 2.537-2.562 (2.543-2.572)

0.38-0.41 (0.37-0.40)

2.490-2.515

U-Npyrrole 2.432-2.480 (2.468-2.471)

0.294 0.435 2.457-2.474 (2.443-2.484)

0.52-0.55 (0.51-0.57)

2.420-2.442

O-Si 1.688 (1.688) 0.574 0.829 1.703 (1.700) 1.04 (1.04) 1.663




SI 28

Fig SI.25: Additional molecular orbitals in the antiferromagnetic singlet state of 2a: (TOP) α-(HOMO-26) with energy of −0.331 a.u. and contributions of 21% endo oxo 2p, 12 % cis oxo 2p and 5% U-5f; (BOTTOM) β-(HOMO-26), with energy of −0.331 a.u. and contributions of 21% endo oxo 2p, 12 % cis oxo 2p and 5% U-5f. Both orbitals are shown with contours of 0.04 (left) and 0.02 (right).

Table SI.3: Truncated NBO analysis of the interaction (Orbital 91) between the uranium atoms of 2a. NBO BETA SPIN (Occupancy) Bond orbital/ Coefficients/ Hybrids --------------------------------------------------------------------------------- 91. (0.99615) BD ( 1) U 47 - U 48 ( 49.96%) 0.7068* U 47 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 0.0000 0.0000 0.0008 0.0003 0.0001 Truncated ( 50.04%) 0.7074* U 48 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 0.0000 0.0000 0.0001 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0005 0.0001 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 Truncated Natural Bond Orbitals (Summary): Principal Delocalizations NBO Occupancy Energy (geminal,vicinal,remote) ==================================================================================== 91. BD ( 1) U 47 - U 48 0.99615 -0.16236 596(r),605(r),632(r),641(r) 1236(r),1255(r),1281(r) 1210(r),586(r),649(r),622(r) 613(r),681(r),614(r),650(r)




SI 29

NATURAL LOCALIZED MOLECULAR ORBITAL (NLMO) ANALYSIS: Maximum off-diagonal element of DM in NLMO basis: 0.26384E-09 Hybridization/Polarization Analysis of NLMOs in NAO Basis, Beta Spin: NLMO/Occupancy/Percent from Parent NBO/ Atomic Hybrid Contributions 91. (1.00000) 99.6142% BD ( 1) U 47 U 48 Truncated 49.767% U47 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 49.847% U48 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) Individual LMO bond orders greater than 0.002 in magnitude, with the overlap between the hybrids in the NLMO given: Atom I / Atom J / NLMO / Bond Order / Hybrid Overlap / U47 U48 91 0.4976682 0.1456220 47 48 189 0.0030057 0.0480590 47 48 202 0.0029710 0.0366442 Truncated NATURAL LOCALIZED MOLECULAR ORBITAL (NLMO) ANALYSIS: Maximum off‐diagonal element of DM in NLMO basis: 0.16237E‐09 Hybridization/Polarization Analysis of NLMOs in NAO Basis, Alpha Spin: NLMO/Occupancy/Percent from Parent NBO/ Atomic Hybrid Contributions ALPHA 91. (1.00000) 99.6132% BD ( 1) U 47 U 48 0.015% C 2 s( 10.67%)p 8.33( 88.89%)d 0.04( 0.44%) 0.011% C 5 s( 0.63%)p99.99( 99.25%)d 0.19( 0.12%) 0.016% C10 s( 9.41%)p 9.58( 90.15%)d 0.05( 0.44%) 0.010% C11 s( 10.28%)p 8.69( 89.38%)d 0.03( 0.34%) 0.012% C18 s( 8.86%)p10.26( 90.86%)d 0.03( 0.28%) 0.016% C19 s( 11.96%)p 7.32( 87.58%)d 0.04( 0.46%) 0.011% C24 s( 0.48%)p99.99( 99.40%)d 0.25( 0.12%) 0.015% C27 s( 9.91%)p 9.05( 89.65%)d 0.05( 0.45%) 0.016% N35 s( 2.78%)p34.14( 94.94%)d 0.82( 2.28%) 0.026% N36 s( 1.56%)p60.83( 95.08%)d 2.15( 3.36%) 0.025% N37 s( 1.48%)p63.91( 94.91%)d 2.43( 3.61%) 0.020% N38 s( 1.85%)p51.73( 95.78%)d 1.28( 2.37%) 0.016% N39 s( 3.01%)p31.48( 94.80%)d 0.73( 2.19%) 0.026% N40 s( 1.48%)p64.28( 95.19%)d 2.24( 3.32%) 0.024% N41 s( 1.37%)p69.36( 94.82%)d 2.79( 3.82%) 0.021% N42 s( 1.37%)p70.13( 96.19%)d 1.78( 2.44%) 49.922% U47 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 49.692% U48 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) BETA 91. (1.00000) 99.6142% BD ( 1) U 47 U 48 0.015% C 2 s( 9.48%)p 9.50( 90.10%)d 0.04( 0.42%) 0.011% C 5 s( 0.53%)p99.99( 99.35%)d 0.23( 0.12%) 0.016% C10 s( 10.66%)p 8.34( 88.91%)d 0.04( 0.44%) 0.010% C18 s( 10.98%)p 8.07( 88.68%)d 0.03( 0.34%) 0.016% C19 s( 11.37%)p 7.76( 88.18%)d 0.04( 0.46%) 0.011% C24 s( 0.56%)p99.99( 99.31%)d 0.24( 0.13%) 0.016% C27 s( 10.55%)p 8.43( 88.99%)d 0.04( 0.45%) 0.017% N35 s( 2.89%)p32.89( 94.96%)d 0.74( 2.15%) 0.027% N36 s( 1.48%)p64.30( 95.18%)d 2.26( 3.34%) 0.025% N37 s( 1.34%)p70.88( 95.02%)d 2.72( 3.64%) 0.019% N38 s( 1.65%)p58.29( 95.90%)d 1.49( 2.46%) 0.017% N39 s( 2.54%)p37.53( 95.16%)d 0.91( 2.31%)




SI 30

0.026% N40 s( 1.55%)p61.43( 94.96%)d 2.26( 3.50%) 0.025% N41 s( 1.40%)p67.82( 94.99%)d 2.58( 3.61%) 0.019% N42 s( 1.78%)p53.98( 95.85%)d 1.34( 2.37%) 49.767% U47 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 49.847% U48 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) Natural Bond Orbitals (Summary): Principal Delocalizations NBO Occupancy Energy (geminal,vicinal,remote) ==================================================================================== ALPHA 91. BD ( 1) U 47 ‐ U 48 0.99613 ‐0.16232 632(r),596(r),605(r),1255(r) 641(r),1236(r),1210(r) 1281(r),613(r),649(r),622(r) BETA 91. BD ( 1) U 47 ‐ U 48 0.99615 ‐0.16236 596(r),605(r),632(r),641(r) 1236(r),1255(r),1281(r) 1210(r),586(r),649(r),622(r) 613(r),681(r),614(r),650(r) (Occupancy) Bond orbital/ Coefficients/ Hybrids ALPHA 91. (0.99613) BD ( 1) U 47 ‐ U 48 ( 50.12%) 0.7079* U 47 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 0.0000 0.0000 0.0004 0.0004 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0002 0.0012 ‐0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0001 ‐0.0021 ‐0.0026 ‐0.0010 0.0000 ‐0.0001 0.0000 0.0000 0.0000 0.0000 ‐0.0012 ‐0.0004 ‐0.0004 0.0000 0.0000 0.0000 0.0000 0.0000 0.0021 0.0063 0.0026 0.0000 0.0000 ‐0.0028 ‐0.0003 0.0002 0.0000 0.0000 0.0063 0.0044 0.0009 0.0000 0.0000 0.0009 ‐0.0005 ‐0.0004 0.0000 0.0000 0.0018 0.0017 0.0003 0.0000 ‐0.0919 ‐0.0193 0.0022 ‐0.0003 0.1826 0.0425 ‐0.0032 0.0007 ‐0.2989 ‐0.0667 0.0068 ‐0.0010 ‐0.1541 ‐0.0354 0.0033 ‐0.0006 0.8654 0.2072 ‐0.0150 0.0036 0.0720 0.0195 ‐0.0015 0.0002 0.1926 0.0468 ‐0.0016 0.0011 ( 49.88%) 0.7063* U 48 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 0.0000 0.0000 0.0009 0.0003 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0008 0.0000 0.0004 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 ‐0.0023 ‐0.0022 ‐0.0009 0.0000 ‐0.0001 0.0000 0.0000 0.0000 0.0001 ‐0.0007 ‐0.0012 ‐0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 ‐0.0058 ‐0.0072




SI 31

‐0.0019 ‐0.0001 0.0000 ‐0.0034 ‐0.0019 ‐0.0003 0.0000 0.0000 0.0011 ‐0.0039 ‐0.0020 0.0000 0.0000 0.0014 0.0005 ‐0.0001 0.0000 0.0000 0.0024 ‐0.0006 ‐0.0005 0.0000 ‐0.1152 ‐0.0291 0.0024 ‐0.0004 0.1880 0.0426 ‐0.0033 0.0008 ‐0.3909 ‐0.0932 0.0081 ‐0.0014 ‐0.1105 ‐0.0263 0.0025 ‐0.0003 0.8143 0.1932 ‐0.0144 0.0034 0.0855 0.0207 ‐0.0018 0.0003 0.2482 0.0638 ‐0.0023 0.0014 BETA 91. (0.99615) BD ( 1) U 47 ‐ U 48 ( 49.96%) 0.7068* U 47 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 0.0000 0.0000 0.0008 0.0003 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0002 0.0006 ‐0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0001 ‐0.0022 ‐0.0026 ‐0.0011 0.0000 ‐0.0001 0.0000 0.0000 0.0000 0.0000 ‐0.0010 ‐0.0008 ‐0.0003 0.0000 0.0000 0.0000 0.0000 0.0000 0.0021 0.0064 0.0027 0.0000 0.0000 ‐0.0013 ‐0.0001 0.0002 0.0000 0.0000 0.0058 0.0044 0.0009 0.0000 0.0000 0.0015 ‐0.0004 ‐0.0003 0.0000 0.0000 0.0031 0.0018 0.0003 0.0000 ‐0.0813 ‐0.0190 0.0018 ‐0.0002 0.1941 0.0448 ‐0.0035 0.0008 ‐0.2996 ‐0.0664 0.0068 ‐0.0010 ‐0.1378 ‐0.0335 0.0028 ‐0.0004 0.8636 0.2066 ‐0.0150 0.0036 0.0922 0.0229 ‐0.0020 0.0003 0.1972 0.0479 ‐0.0017 0.0011 ( 50.04%) 0.7074* U 48 s( 0.00%)p 0.00( 0.00%)d 1.00( 0.01%) f99.99( 99.99%) 0.0000 0.0000 0.0001 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0005 0.0001 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 ‐0.0024 ‐0.0023 ‐0.0009 0.0000 ‐0.0001 0.0000 0.0000 0.0000 0.0000 ‐0.0006 ‐0.0008 ‐0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 ‐0.0064 ‐0.0073 ‐0.0019 ‐0.0001 0.0000 ‐0.0013 ‐0.0013 ‐0.0002 0.0000 0.0000 0.0017 ‐0.0038 ‐0.0020 0.0000 0.0000 0.0012 0.0007 0.0000 0.0000 0.0000 0.0010 ‐0.0009 ‐0.0005 0.0000 ‐0.1263 ‐0.0310 0.0026 ‐0.0004 0.1979 0.0461 ‐0.0035 0.0008 ‐0.3784 ‐0.0905 0.0078 ‐0.0014 ‐0.1384 ‐0.0325 0.0031 ‐0.0005 0.8094 0.1920 ‐0.0142 0.0034 0.0923 0.0207 ‐0.0021 0.0003 0.2540 0.0651 ‐0.0025 0.0014




SI 32

Fig SI.26: The bonding (upper left) and antibonding (upper right) orbitals between the uranium centres. The two actinide atoms have similar chemical environments. This is in line with the general expectation of covalent interactions in homo-bimetallic systems. A cut-off value of 0.04 was used to generate the two upper orbital pictures shown. The series of lower figures are drawn with 0.02, 0.04, 0.08, and 0.12 cut-off values (left to right).

Fig SI.27: The calculated spin density in the antiferromagnetic unrestricted singlet electronic state obtained with the B3LYP functional and actinide pseudopotentials. This electronic state can be described as an fαfβ configuration with electrons of different spins localized on each uranium atom. The ferromagnetic triplet state has an fαfα configuration.




SI 33

Fig SI.28: Colour version of Figure 3 in the paper. Molecular orbitals of primary σ- and π- character in the unrestricted singlet state of 2a: (a) α-(HOMO-27) with energy of –0.333 a.u. and contributions of 27% endo-oxo 2p, 13 % exo-oxo 2p, 3 % cis-oxo 2p and 13 % U-5f; (b) β-(HOMO-27), with energy of –0.333 a.u. and contributions of 25 % endo-oxo 2p, 11 % exo-oxo 2p, 3 % cis-oxo 2p and 13% U-5f. These σ-type orbitals extend across the U2O2 core; (c) α-HOMO-28 with energy of –0.334 a.u. and contributions of 34 % cis-oxo 2p and 9 % endo-oxo 2p, 5% U-5f and 6 % U-6d; (d) β-HOMO-28, with energy of –0.334 a.u. and contributions of 37 % cis-oxo 2p, 9 % endo-oxo 2p, 5 % U-5f and 5 % U-6d. These orbitals depict the weaker π-type interaction across the U2O2 core. (e) HOMO-145 (bonding with respect to the two U atoms) with an energy of –1.094 a.u. and (f) its antibonding counterpart, both predominantly U-5f, with very minor components from the O 2s orbitals. All the drawings have an isocontour value of 0.02.




SI 34

Table SI.4: The optimized structure of the antiferromagnetic singlet electronic state obtained with the B3LYP functional and actinide pseudopotentials for 2a.

C 7.383458000 4.635724000 5.867562000 C 7.571950000 3.984936000 7.099584000 C 7.972666000 4.501193000 8.346126000 C 7.922857000 3.434047000 9.242329000 C 7.490707000 2.299059000 8.514737000 C 7.138535000 0.927851000 9.067800000 C 7.643107000 -0.196769000 8.178257000 C 8.205703000 -1.429304000 8.589873000 C 8.374688000 -2.205619000 7.444521000 C 7.912996000 -1.423318000 6.369461000 C 7.798098000 -1.738281000 5.004537000 C 7.277690000 -1.251703000 2.768247000 C 8.462227000 -1.665850000 2.143410000 C 8.517847000 -2.051319000 0.801752000 C 7.332374000 -2.018711000 0.040699000 C 6.149772000 -1.606403000 0.659848000 C 6.089607000 -1.225244000 2.007553000 C 3.825504000 -1.655805000 2.453173000 C 2.549331000 -1.319220000 2.939621000 C 1.351430000 -2.057864000 2.934047000 C 0.410433000 -1.277199000 3.605491000 C 1.065140000 -0.086605000 4.003223000 C 0.511526000 1.026285000 4.878824000 C 0.891067000 2.402516000 4.355752000 C 0.072826000 3.556072000 4.291518000 C 0.884582000 4.612028000 3.877235000 C 2.171330000 4.070695000 3.698693000 C 3.378623000 4.698437000 3.342661000 C 5.668746000 4.717380000 2.825352000 C 5.644011000 5.447712000 1.629107000 C 6.745569000 6.164989000 1.155898000 C 7.935079000 6.152251000 1.911192000 C 7.964690000 5.420636000 3.100917000 C 6.860949000 4.701237000 3.579975000 N 6.943084000 3.993745000 4.805948000 N 7.288062000 2.626445000 7.216915000 N 7.474321000 -0.186147000 6.835279000 N 7.278901000 -0.891773000 4.139734000 N 4.510707000 4.030477000 3.270577000 N 2.157420000 2.708478000 3.989093000 N 2.355007000 -0.105008000 3.593668000 N 4.854502000 -0.846776000 2.592624000 O 9.052122000 1.660004000 4.712042000 O 4.955376000 1.302681000 5.193268000 O 6.275039000 1.677565000 3.107216000 O 3.593779000 1.742152000 1.305076000 U 7.037150000 1.467044000 5.050900000 U 4.188258000 1.512496000 3.258635000 H 8.770320000 -3.211344000 7.380957000 H 8.445123000 -1.716474000 9.603380000 H 9.374338000 -1.672235000 2.734366000 H 5.235117000 -1.559768000 0.075398000 H 1.206227000 -3.039322000 2.500754000 H -0.619931000 -1.536563000 3.800809000 H 0.598410000 5.645577000 3.729014000 H -0.978749000 3.608725000 4.533331000 H 4.729480000 5.434827000 1.042775000 H 8.882767000 5.390488000 3.681485000 H 8.154982000 3.467710000 10.296841000 H 8.249553000 5.526686000 8.555293000 H 7.590051000 5.707277000 5.806884000

H 8.130575000 -2.723161000 4.666483000 H 3.959784000 -2.626358000 1.968590000 H 3.369016000 5.773212000 3.143683000 C 7.330717000 -2.405623000 -1.418916000 H 8.002232000 -1.768264000 -2.007153000 H 7.669880000 -3.438560000 -1.565448000 H 6.329717000 -2.319509000 -1.849540000 C 9.829558000 -2.476652000 0.186581000 H 10.639044000 -2.446455000 0.920656000 H 9.778643000 -3.497130000 -0.212626000 H 10.114320000 -1.826027000 -0.649319000 C 6.655844000 6.922493000 -0.147287000 H 7.392259000 6.562491000 -0.876163000 H 5.665205000 6.818482000 -0.597456000 H 6.849143000 7.993409000 -0.008427000 C 9.163473000 6.897106000 1.446161000 H 9.988094000 6.781231000 2.154387000 H 9.510072000 6.536600000 0.469874000 H 8.968603000 7.970718000 1.333369000 C 1.126119000 0.867309000 6.303765000 H 0.740359000 1.646976000 6.969007000 H 0.862952000 -0.110844000 6.719928000 H 2.214739000 0.947891000 6.270939000 C -1.019701000 0.902709000 4.995116000 H -1.509771000 1.006076000 4.022459000 H -1.292960000 -0.067455000 5.418419000 H -1.414681000 1.671479000 5.664470000 Si 2.637653000 1.864516000 -0.081013000 C 0.827320000 1.695755000 0.401761000 H 0.177033000 1.771314000 -0.477889000 H 0.636847000 0.730211000 0.881809000 H 0.534184000 2.479654000 1.107910000 C 3.149521000 0.481923000 -1.257220000 H 4.220127000 0.532218000 -1.481848000 H 2.939684000 -0.499097000 -0.817447000 H 2.602227000 0.544890000 -2.204916000 C 2.967891000 3.549036000 -0.862500000 H 4.034696000 3.685696000 -1.068418000 H 2.424383000 3.660057000 -1.807986000 H 2.643721000 4.356551000 -0.197143000 Si 10.735688000 1.748749000 4.786373000 C 11.338863000 0.512111000 6.071126000 H 10.942860000 0.757174000 7.062003000 H 11.007306000 -0.503229000 5.831086000 H 12.433205000 0.506081000 6.135555000 C 11.213778000 3.505214000 5.276760000 H 10.711012000 3.803740000 6.202558000 H 12.295090000 3.589013000 5.436527000 H 10.937616000 4.221603000 4.495509000 C 11.408953000 1.336925000 3.074431000 H 12.504348000 1.378117000 3.056978000 H 11.105281000 0.333177000 2.759528000 H 11.032999000 2.043998000 2.327348000 C 5.582809000 0.823932000 9.132537000 H 5.143026000 0.930930000 8.138597000 H 5.287365000 -0.148612000 9.540069000 H 5.179525000 1.611897000 9.777300000 C 7.693428000 0.769225000 10.496474000 H 7.291028000 1.547070000 11.150666000 H 7.394244000 -0.194167000 10.917458000 H 8.785576000 0.831116000 10.516693000




SI 35

References 1 Givaja, G. et al. Design and synthesis of binucleating macrocyclic clefts derived from Schiff‐

base calixpyrroles. Chem. Eur. J. 13, 3707‐3723, (2007). 2 Barnhart, D. M., Burns, C. J., Sauer, N. N. & Watkin, J. G. Synthesis of neutral and anionic

uranyl aryloxide complexes from uranyl amide precursors: X‐ray crystal structures of UO2(O‐2,6‐iPr2C6H3)2(py)3 and [Na(THF)3]2[UO2(O‐2,6‐Me2C6H3)4]. Inorg. Chem. 34, 4079‐4084, (1995).

3 Wilkerson, M. P., Burns, C. J., Paine, R. T. & Scott, B. L. Synthesis and Crystal Structure of UO2Cl2(THF)3: A Simple Preparation of an Anhydrous Uranyl Reagent. Inorg. Chem. 38, 4156‐4158, (1999).

4 Mansell, S. M., Perandones, B. F. & Arnold, P. L. New U(III) and U(IV) silylamides and an improved synthesis of NaN(SiMe2R)2 (R = Me, Ph). J. Organomet. Chem. 695, 2814‐2821, (2010).

5 Arnold, P. L. et al. Single‐electron uranyl reduction by a rare‐earth cation. Angew. Chem., Int. Ed. 50, 887‐890, (2011).

6 Nocton, G. et al. Synthesis, Structure, and Bonding of Stable Complexes of Pentavalent Uranyl. J. Am. Chem. Soc. 132, 495‐508, (2010).

7 Rinehart, J. D., Harris, T. D., Kozimor, S. A., Bartlett, B. M. & Long, J. R. Magnetic Exchange Coupling in Actinide‐Containing Molecules. Inorg. Chem. 48, 3382‐3395, (2009).

8 Kuchle, W., Dolg, M., Stoll, H. & Preuss, H. Ab initio pseudopotentials for Hg through Rn .1. Parameter sets and atomic calculations. Mol. Phys. 74, 1245‐1263, (1991).

9 Kuchle, W., Dolg, M., Stoll, H. & Preuss, H. Energy‐adjusted pseudopotentials for the actinides ‐ parameter sets and test calculations for thorium and thorium monoxide. J. Chem. Phys. 100, 7535‐7542, (1994).

10 Gaussian 09, Revision A.2 (Gaussian, Inc., Wallingford CT, 2009). 11 Priroda Code 6 (2006). 12 Laikov, D. N. A new class of atomic basis functions for accurate electronic structure

calculations of molecules. Chem. Phys. Lett. 416, 116‐120, (2005).


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