In te format proided b te autors and unedited. Elucidating ... · such time, the solution was treated with a single equivalent of LiCH 2TMS (10 mg, 0.102 mmol) slowly, and the solution

In the format provided by the authors and unedited.

Elucidating bonding preferences intetrakis(imido)uranate(VI) dianions

S1

Supplementary Material for:

Elucidating Bonding Preferences in Tetrakis(imido)uranate(VI) Dianions

Nickolas H. Anderson,1 Jing Xie,2 Debmalya Ray,2 Matthias Zeller,1,3 Laura Gagliardi,2 Suzanne C. Bart*1

1 H.C. Brown Laboratory, Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States

2 Department of Chemistry, Supercomputing Institute, and Chemical Theory Center, University of Minnesota, Minneapolis, Minnesota 55455, United States

3 Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, United States

*Correspondence to: [email protected]

Table of Contents

I. General Procedures and Materials and Methods p. S2

II. Synthesis and Characterization of Complexes p. S3

III. Spectroscopy p. S10

IV. Computational Methods p. S20

V. Discussion of Computational Results p. S22

VI. X-ray Structural Determination p. S34

VII. References p. S46

© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NCHEM.2767

NATURE CHEMISTRY | www.nature.com/naturechemistry 1

http://dx.doi.org/10.1038/nchem.2767

S2

I. General Procedure and Materials and Methods

General Procedures and Materials

All air- and moisture-sensitive manipulations were performed by using standard Schlenk

techniques or in an MBraun inert atmosphere drybox with an atmosphere of purified nitrogen. The

MBraun drybox was equipped with a coldwell designed for freezing samples in liquid nitrogen as

well as two -35 °C freezers for cooling samples and crystallizations. Solvents for sensitive

manipulations were dried and deoxygenated by using literature procedures.1 Benzene-d6,

Toluene-d8, and THF-d8 were purchased from Cambridge Isotope Laboratories, dried with

molecular sieves and sodium, and degassed by 3 freeze–pump–thaw cycles. 2,6-

diisopropylphenyl azide,2 U(NDIPP)3(THF)3,3 and UI3(THF)4,4 were prepared according to

literature procedures. Rubidium graphite and cesium graphite were synthesized via a similar

method for that described for potassium graphite.5

1H and 13C NMR spectra were recorded on a Varian Inova 300 spectrometer operating at 299.992

MHz. All chemical shifts are reported relative to the peak for SiMe4, using 1H and 13C (residual)

chemical shifts of the solvent as a secondary standard. The spectra for paramagnetic molecules

were obtained by using an acquisition time of 0.5, thus the peak widths reported have an error of

±2 Hz. For paramagnetic molecules, the 1H NMR data are reported with the chemical shift,

followed by the peak width at half height in Hertz, the integration value, and where possible, the

peak assignment. Infrared spectra were recorded on a Thermo Nicolet 6700 FTIR

spectrophotometer with a DTGS TEC detector as a solution deposition on a KBr window.

Samples were transferred under an inert atmosphere until transferred to the spectrometer.

Electronic absorption measurements were recorded at 294 K in THF in sealed 1 cm quartz

cuvettes with data collection being performed on a Jasco V-6700 spectrophotometer under inert

conditions. Elemental analyses were performed by Complete Analysis Laboratories Incorporated

on dried powder samples shipped in sealed vessels bearing an inert atmosphere.

S3

II. Synthesis and Characterization of Complexes

Preparation of 2-Li. In a 20 mL scintillation vial, an Et2O solution of 1 (100 mg, 0.102 mmol) was

treated with a single equivalent of LiNHDIPP (18 mg, 0.102 mmol) and let stir for 5 minutes. After

such time, the solution was treated with a single equivalent of LiCH2TMS (10 mg, 0.102 mmol)

slowly, and the solution was allowed to stir for an additional 30 min at room temperature. Excess

solvent was removed in vacuo resulting in isolation of 2-Li in good yield (100 mg, 0.098 mmol,

97%).

1H NMR (300 MHz, C6D6, 25 ºC, TMS) δ = 1.46 (d, 3J(H,H) = 6.8 Hz, 48H, iPrCH3), 4.53 (sept,

3J(H,H) = 6.8 Hz, 8H, iPrCH), 5.56 (t, 3J(H,H) = 7.6 Hz, 4H, p-ArH), 7.76 (d, 3J(H,H) = 7.6 Hz, 8H,

m-ArH).

13C NMR (300 MHz, C6D6, 25 ºC, TMS) δ = 25.9 (iPrCH3), 27.0 (iPrCH), 117.68 (m-CH), 124.0 (p-

CH), 154.2 (i-C), 156.8 (o-C).

IR (KBr plate): = 3046 (w), 2957 (vs), 2866 (s), 1581(w), 1460 (s), 1423 (s), 1408 (w), 1315 (s),

1237 (vs), 1202 (s), 1110 (w), 895 (w), 747 (s).

analysis (calcd., found for C64H100N4Li2O4U): C (62.75, 62.58), H (8.67, 8.51), N (4.30, 4.36).

S4

Alternative preparation of 2-Li. In a 20 mL scintillation vial, an Et2O solution of 1 (100 mg, 0.102

mmol) was treated with a single equivalent of NH2DIPP (18 mg, 0.102 mmol) and let stir for 5

minutes. After such time, the solution was treated with two equivalents of LiCH2TMS (20 mg,

0.204 mmol) slowly, and the solution was allowed to stir for an additional 30 min at room

temperature. Excess solvent was removed in vacuo and analysis by 1H NMR spectroscopy

revealed formation of 2-Li in good yield (88 mg, 0.094 mmol, 92%).

S5

Preparation of 2-Na. In a 20 mL scintillation vial, an Et2O solution of 1 (100 mg, 0.102 mmol)

was treated with a single equivalent of NaNHDIPP (20 mg, 0.102 mmol) and let stir for 5 minutes.

After which time, the solution was treated with a single equivalent of NaCH2TMS (10 mg, 0.102

mmol), slowly, and the solution was left to stir for an additional 30 min. Excess solvent was

removed in vacuo and a brown solid identified as 2-Na was collected in good yield. (Yield; 103

mg, 0.098 mmol, 97%) Crystals of 2-Na were grown by slow evaporation of a concentrated Et2O

solution of 2-Na at -34 °C.



m-ArH).

13C NMR (300 MHz, C6D6, 25 ºC, TMS) δ = 26.0 (iPrCH), 26.0 (iPrCH3), 117.2 (m-CH), 122.9 (p-

CH), 153.8 (i-C), 160.3 (o-C).


1238 (vs), 1206 (s), 1107 (w), 886 (w), 745 (s).

analysis (calcd., found for C64H100N4Na2O4U): C (59.78, 59.73), H (8.03, 7.94), N (4.65, 4.88).

S6

Preparation of 2-Na. In a 20 mL scintillation vial, an Et2O solution of 1 (100 mg, 0.102 mmol)

was treated with a single equivalent of NH2DIPP (18 mg, 0.102 mmol) and let stir for 5 minutes.

After which time, the solution was treated with a two equivalents of NaCH2TMS (20 mg, 0.102

mmol), slowly, and the solution was left to stir for an additional 30 min. Excess solvent was

removed in vacuo and analysis of the crude material by 1H NMR spectroscopy revealed formation

of 2-Na in good yield.

S7

Reductive synthesis of 2-K. In a 20 mL scintillation vial, an Et2O solution (~10 mL) solution of 1

(100 mg, 0.102 mmol) was added a single equivalent of KC8 (14 mg, 0.102 mmol) resulting in a

slight darkening of the solution. After 5 minutes of vigorous stirring, a single equivalent of N3DIPP

(20 mg, 0.102 mmol) was added to the solution in a dropwise fashion, with each addition resulting

in a vigorous release of N2. Following another 5 minute reaction period, a second equivalent of

KC8 (14 mg, 0.102 mmol) was added slowly over several minutes (5-10 mg aliquots), resulting

again in effervescence of N2, and the solution was stirred for an additional 30 minutes. Following

filtration and removal of excess solvent in vacuo, a dark brown solid identified as [U(NDIPP)4][K2]

(2-K) could be isolated in good yield. (Yield; 105 mg, 0.097 mmol, 96%) Crystals of 2-K were

grown from a concentrated THF/pentane solution containing 2-K at -34 °C. Crystals of [(2.2.2-

Crypt-K)]2[U(NDIPP)]4 (2-K(crypt)) were grown from a concentrated THF solution of 2-K and two

equivalents of 2.2.2-Cryptand at -34 °C.


3J(H,H) = 6.9 Hz, 8H, iPrCH), 5.07 (t, 3J(H,H) = 7.6 Hz, 4H, p-ArH), , 7.79 (d, 3J(H,H) = 7.6 Hz,

8H, m-ArH).

13C NMR (75 MHz, C6D6, 25 ºC, TMS) δ = 25.7 (iPrCH), 26.0 (iPrCH3), 117.4 (m-CH), 121.3 (p-

CH), 149.3 (i-C), 161.2 (o-C).


1243 (vs), 1134 (w), 895 (w), 747 (s).

analysis (calcd., found for C64H100N4K2O4U): C (56.71, 56.71), H (6.74, 6.67), N (5.51, 5.24).

S8

Synthesis of 2-Rb. In a 20 mL scintillation vial, a stirring Et2O solution of 1 (100 mg, 0.102 mmol)

was added a single equivalent of RbC8 (18 mg, 0.102 mmol), resulting in a darkening of the

solution. After 5 minutes of vigorous stirring, a single equivalent of N3DIPP (20 mg, 0.102 mmol)

was added to the solution in a dropwise fashion. Following another 5-minute reaction period, a

second equivalent of RbC8 (18 mg, 0.102 mmol) was added slowly over several minutes (5-10

mg aliquots) and the solution was stirred for an additional 30 minutes. Following filtration and

removal of excess solvent in vacuo, a dark brown solid identified as [U(NDIPP)4][Rb2] (2-Rb)

could be isolated. (Yield; 100 mg, 0.085 mmol, 84%) Crystals of 2-Rb were grown from a

concentrated THF solution containing 2-Rb at -34 °C.



m-ArH); 1H NMR (300 MHz, THFd8, 25 ºC, TMS) δ = 1.30 (d, 3J(H,H) = 6.8 Hz, 48H, iPrCH3),

4.59 (t, 3J(H,H) = 7.4 Hz, 4H, p-ArH), 4.73 (sept, 3J(H,H) = 6.8 Hz, 8H, iPrCH3), 7.53 (d, 3J(H,H)

= 7.4 Hz, 8H, m-ArH).

13C NMR (300 MHz, THFd8, 25 ºC, TMS) δ = 26.1 (iPrCH), 26.6 (iPrCH3), 117.2 (m-CH), 120.3

(p-CH), 148.9 (i-C), 163.4 (o-C).


1245 (vs), 1110 (w), 892 (w), 752 (s), 745 (s).

analysis (calcd., found for C64H100N4Rb2O4U): C (51.94, 51.78), H (6.17, 6.16), N (5.05, 5.09).

S9

Preparation of 2-Cs. In a 20 mL scintillation vial, a stirring Et2O solution of 1 (100 mg, 0.102

mmol) was added a single equivalent of CsC8 (23 mg, 0.102 mmol), resulting in a darkening of

the solution. After 5 minutes of vigorous stirring, a single equivalent of N3DIPP (20 mg, 0.102

mmol) was added to the solution in a dropwise fashion. Following another 5-minute reaction

period, a second equivalent of CsC8 (23 mg, 0.102 mmol) was added slowly over several minutes

(5-10 mg aliquots). The solution was stirred for an additional 30 minutes, during which time a dark

brown solid precipitated from the solution. Filtration allowed for isolation of this dark solid which

was filtered once more with THF to separate the graphite, isolating pure [U(NDIPP)4][Cs2] (2-Cs)

as a dark brown solid, after removal of the volatiles in vacuo. (Yield; 115 mg, 0.089 mmol, 89%).

Crystals of 2-Cs were grown from a concentrated THF/toluene solution containing 2-Cs at -34 °C.



m-ArH); 1H NMR (300 MHz, THFd8, 25 ºC, TMS) δ = 1.32 (d, 3J(H,H) = 6.8 Hz, 48H, iPrCH3),

4.59 (t, 3J(H,H) = 7.5 Hz, 4H, p-ArH), 4.77 (sept, 3J(H,H) = 6.8 Hz, 8H, iPrCH3), 7.54 (d, 3J(H,H)

= 7.5 Hz, 8H, m-ArH).

13C NMR (300 MHz, THFd8, 25 ºC, TMS) δ = 26.1 (iPrCH), 26.6 (iPrCH3), 117.4 (m-CH), 120.0

(p-CH), 148.9 (i-C), 163.7 (o-C).


1247 (vs), 1110 (w), 893 (w), 752 (s), 745 (s).

Analysis (calcd., found for C64H100N4Cs2O4U): C (47.85, 47.99), H (5.69, 5.78), N (4.65, 4.38).

S10

III. Spectroscopy

Supplementary Fig. 1; 1H NMR spectrum of 2-Li in benzene-d6. Resonance located at ca. 2.8

ppm and 0.8 are attributed to partially bound Et2O in solution.

Supplementary Fig. 2; 1H NMR spectrum of 2-Na in benzene-d6. Resonance located at ca. 3.8

ppm to partially bound Et2O in solution resonances at 0.85 and 1.2 ppm are residual pentane in

solution.

S11

Supplementary Fig. 3; 1H NMR spectrum of a powdered sample of 2-K in benzene-d6. Resonance located at ca. 3.6 ppm is attributed to free THF and resonances at 0.85 and 1.2 are residual pentane in solution.

Supplementary Fig. 4; 1H NMR spectrum of 2-Rb in benzene-d6. Excess tetrahydrofuran was added to assist with solubility. Resonance located at ca. 3.2 ppm and 1.4 attributed to free Et2O in solution.

S12

Supplementary Fig. 5; 1H NMR spectrum of 2-Rb in tetrahydrofuran-d8.

Supplementary Fig. 6; 1H NMR spectrum of 2-Cs in benzene-d6. Excess tetrahydrofuran was added to assist with solubility.

S13

Supplementary Fig. 7; 1H NMR spectrum of 2-Cs in tetrahydrofuran-d8.

Supplementary Fig. 8; Variable temperature 1H NMR spectra of 2-Na in toluene-d8 from 50 - -30 ºC in 10 ºC intervals

S14

Supplementary Fig. 9; 1H NMR of 2-K(crypt) in thf-d8 at 25 ºC. Spectrum shows three distinct sets of resonances throughout the diamagnetic region assigned to K2U(NDIPP)4, with both K ions associated, KU(NDIPP)4-(KCrypt), with one K ion associated and one dissociated, and U(NDIPP)4-(KCrypt)2, with both K ions dissociated. Despite the inclusion of excess Cryptand, the three species appear to be in equilibrium with one another. Only broadened resonances of free Cryptand are noted.

1234567

S15

Supplementary Fig. 10; Infrared spectrum of 2-Li as a deposition onto a KBr salt plate.

Supplementary Fig. 11; Infrared spectrum of 2-Na as a deposition onto a KBr salt plate.

S16

Supplementary Fig. 12; Infrared spectrum of 2-K as a deposition onto a KBr salt plate.

Supplementary Fig. 13; Infrared spectrum of 2-Rb as a deposition onto a KBr salt plate.

S17

Supplementary Fig. 14; Infrared spectrum of 2-Cs as a deposition onto a KBr salt plate.

S18

Supplementary Fig. 15; Stacked infrared plot highlighting the fingerprint region of the spectra (1800 – 500 cm-1) to display the U=N-C stretching vibration (1240 cm-1)

S19

Supplementary Table 1; Data corresponding to the shifts (ppm) of the DIPP resonances of 2 by 1H NMR spectroscopy and the energy of the U=N-C coupled vibrations seen by IR spectroscopy.

Supplementary Fig. 16; Electronic absorption spectra of 2-Li – 2-Cs in THF from 300 – 2100 nm. The spectra have been segmented and staggered to highlight the near-infrared region (800 – 1200 nm) of the spectrum.

2-Li 2-Na 2-K 2-Rb 2-Cs Signal Shift (ppm) iPr-CH3 1.46 1.45 1.48 1.52 1.53 iPr-CH 4.55 4.60 4.66 4.73 4.81 p-Ar-H 5.56 5.22 5.07 5.02 4.97 m-Ar-H 7.76 7.79 7.78 7.81 7.80

Vibration Energy (cm-1) U=N-C 1237 1238 1243 1245 1247

S20

IV. Computational Methods

Density functional theory (DFT) calculations were carried out with the ADF 2013 package6

while employing the scalar-relativistic Zeroth order regular approximation (ZORA)7 with all-

electron Slater type basis sets of triple-ζ quality with two polarization functions (TZ2P). This

combination of basis set and the scalar-relativistic approximation has been shown8 to provide

accurate descriptions of the structural, bonding, electronic and magnetic properties of

actinide species when employed with appropriate functionals within the Kohn-Sham DFT

formalism. The Perdew-Burke-Ernzerhof (PBE)9,10 density functional was used in these

calculations. This level of theory is denoted as PBE/ZORA/TZ2P in this manuscript. An

integration parameter of 6.0 was employed for all the calculations. Geometry optimizations

were followed by vibrational frequency analyses using the harmonic approximation. The

vibrational frequency calculations were used to determine the nature of the optimized

structures on the corresponding potential energy surfaces. In all cases, the structures were

optimized until the convergence criteria energy of 1×10-3 Hartree and gradient of 1×10-3

Hartree/Å were attained. To examine the generality of the findings obtained from PBE

functional, calculations were performed with the dispersion corrected functional PBE-D3(43)

and meta-GGA functional M06-L12 with ZORA/TZ2P.

Single point natural bond orbital (NBO) analysis was performed at the PBE/ZORA/TZ2P

optimized geometry of see-saw 2-Li – 2-Cs compounds. The Gaussian 09 package13 was

employed and the NBO analysis was based on the orbitals obtained from PBE/6-

311G(2d,2p)&SDD calculations. The 6-311G(2d,2p)&SDD notation means that 6-

311G(2d,2p) basis set was used on C, N, H, and Li, while SDD pseudo potentials and

corresponding basis set were used on Na, K, Rb, Cs, and U.

Ab initio calculations by means of the complete active space SCF method (CASSCF)14

were performed to characterize compounds 2-Li – 2-Cs. To reduce the computational cost, a

truncated model (denoted 2b) from compound 2 was designed, where the isopropyl groups

attached to the benzene rings were replaced with hydrogen atoms. CASSCF calculations

were performed using the MOLCAS-8.1 package.15 Relativistic basis sets of atomic natural

S21

orbital type of double-ζ quality (ANO-RCC-VDZ)16 were used for the uranium, nitrogen,

carbon, and hydrogen atoms. Scalar relativistic effects were included using the Douglas-

Kroll-Hess Hamiltonian.17-19 The computational cost arising from the two-electron integrals

was drastically reduced by employing the Cholesky decomposition technique. The

decomposition threshold was chosen to be 10-4, as this should correspond to an accuracy in

total energies of the order of mHartree or higher. Compound 2b belongs to the C1 point

group. The CASSCF calculations were performed at the PBE-optimized geometry, which is in

agreement with the experimental geometry.

S22

V. Discussion of computational results

DFT calculations of 2-Li – 2-Cs, using the molecular formula [M]2[U(NDIPP)4], were

performed with PBE and PBE-D3 functional using ZORA/TZ2P. Optimized structures of 2-Na, 2-

Rb, and 2-Cs are consistent with the experimentally determined structures, with maximum bond

length differences of 0.02, 0.18, 0.06 Å (PBE) and of 0.04, 0.20, 0.06 Å (PBE-D3), for 2-Na, 2-Rb,

and 2-Cs, respectively (tables S4-8,10). Crystal structures were not available for 2-Li or 2-K at

the time of analysis. Our optimized structures for these two systems are consistent with those for

2-Na, 2-Rb, and 2-Cs. Overall, PBE and PBE-D3 give quite similar structures. In addition to

[M]2[U(NDIPP)4], structures with formula (Et2O-Na)2U(NDIPP)4(THF), (Ph-Rb)2U(NDIPP)4, and

(Ph-Cs)2U(NDIPP)4, which resemble the crystal structures of 2-Na, 2-Rb, and 2-Cs in fig. 3,

respectively, were optimized with PBE/ZORA/TZ2P method. Inspection of Tables S5,7-8 shows

that the addition of extra ligands (Et2O and THF for Na species, and Ph for Rb species and Cs

species) to the [M]2[U(NDIPP)4] model elongates the U-N, U-M, and M-N bond distances by 0.01-

0.08 Å. The three optimized structures with extra ligands are consistent with experimental

structures, with respective maximum bond length differences of 0.05, 0.15, 0.05 Å.

To rationalize the experimental geometry (pseudo-seesaw) of this uranium tetrakis(imido)

family, compounds 2-Li – 2-Cs were optimized by imposing the square planar and tetrahedral

constraints, respectively, of the UN4 cores. Alternately, optimizations without imposing tetrahedral

or square planar constraints ended to a pseudo-seesaw structure. Both the PBE and PBE-D3

functional with ZORA/TZ2P method were used. The relative energy differences are tabulated in

table S2-S3. Both PBE and PBE-D3 calculations indicate that the pseudo-seesaw structure is the

most stable compared to the corresponding tetrahedron and square-plane isomers. It is notable

that the energy difference between the tetrahedral and distorted seesaw structure drastically

decreased, (PBE, 32.64 to 7.55 kcal/mol; PBE-D3 24.73-9.39 kcal/mol) as the alkali metal goes

from Li to Cs. On the other hand, the energy difference between the square-planar and distorted

seesaw structures increases moderately, (PBD 10.91 – 16.09 kcal/mol; PBE-D3, 11.49 to 18.94

kcal/mol), as the alkali metal is changed from Li to Cs.

S23

Given the cation effect and the deviation of these structures from ideal tetrahedral or square-

planar structures, a family of tetrakis(oxo) and tetrakis(imido) dianion complexes (UO42-, U(NH)4

2-,

U(NMe)42-, U(NPh)4

2-, and U(NDIPP)42-) and their corresponding neutral complexes (Na2UO4,

Na2U(NPh)4) were analyzed with the PBE, PBE-D3, and M06-L functionals and the ZORA/TZ2P

method. As was observed with PBE, optimizations of dianionic complexes with both PBE-D3 and

M06-L functional agree with the original report of UO42- and display tetrahedral coordination

geometry.20 The only exception is that U(NDIPP)42- displays pseudo-C2v geometry with two large

(experimental, 114° and 122°; PBE, 123°; PBE-D3, 117°; M06-L, 119° and 114° ) and two small

(experimental, 105°; PBE, 101° and 104°; PBE-D3, 100° and 104°; M06-L, 106°) N-U-N angles,

due to the steric effect of the DIPP substituents (Table 1, table S10-12). The calculated structures

are overall in good agreement with the crystal structures of U(NDIPP)42-, where M06-L gives the

best agreement. The addition of the Na+ counter cations to the dianionic complexes leads to

structural changes. The Na2UO4 species has a C2v square-planar structure with two identical O-

U-O bonding angles of 167° (PBE and PBE-D3), and 173° (M06-L. All the four functionals predict

the optimized Na2U(NPh)4 to adopt a seesaw structure nearly identical to 2. In brief, the above

calculations show that the structural changes of 2 arise from the cation coordination and/ or the

sterics of the iPr substituents.

To elucidate the U-N bond characters of compound 2, we carried out CASSCF calculations

on a truncated compound (denoted as 2b) from compound 2. We selected an active space of

eight electrons in eight orbitals, CAS(8,8), including 2 electrons from each U-N π-bond, making a

total of 8 electrons. The active and inactive orbitals for compounds 2b-Li – 2b-Cs are similar in

shape and occupation to those of 2b-Na, so only the 2b-Na orbitals are showed in

Supplementary Figure 18 as a representative case. In 2b-Na CAS(8,8) active space, the four

doubly occupied orbitals (π1 – π4) are N-U-N three-center π-type orbitals along the axial

direction, together with four anti-π-bonding orbitals (π5 – π8). In its inactive space, we found four

N-U-N π-type orbitals along the equatorial direction, one axial σ-type orbital, and one equatorial

σ-type orbital, where the σ-type orbitals mainly involve N-C bond. The main electronic

S24

configuration π12 π22 π32 π42 π50 π60 π70 π80 has a weight of 0.88, and similar weights have

been found for 2-Li – 2-Cs.

S25

Supplementary Fig. 17. Molecular orbital depictions of 2-Rb including HOMO – HOMO-7, HOMO-12 and HOMO-14 using the PBE/ZORA/TZ2P level of theory. Computed structure of 2-Rb has been included in an identical orientation for clarity.

Supplementary Fig. 18. The active orbitals (π1 – π8) in the CAS(8,8) calculation and the representative inactive orbitals (πi1 – πi4, σ1 – σ2) for 2b-Na. The occupation number for each orbital is given in parentheses.

S26

Supplementary Table 2. Relative energies (kcal/mol) for three isomers of M2U(NDIPP)4, M = Li, Na, K, Rb, Cs, using the PBE/ZORA/TZ2P level of theory.

relative energy (kcal/mol)

M pseudo-seesaw tetrahedron square-plane 2-Li 0 32.6 10.9 2-Na 0 17.8 13.8 2-K 0 13.1 15.4

2-Rb 0 8.1 15.7 2-Cs 0 7.6 16.1

Supplementary Table 3. Relative energies (kcal/mol) for three isomers of M2U(NDIPP)4, M = Li, Na, K, Rb, Cs, using the PBE-D3/ZORA/TZ2P level of theory.

relative energy (kcal/mol) M pseudo-seesaw tetrahedron square-plane

2-Li 0 24.7 11.5 2-Na 0 19.2 12.9 2-K 0 13.3 14.2

2-Rb 0 9.9 14.9 2-Cs 0 9.4 18.5

Supplementary Table 4. Calculated bond metrics of 2-Li at PBE/ZORA/TZ2P level of theory for three isomers.

Li2U(NDIPP)4

Calculated stereo-isomers square-plane tetrahedron pseudo-seesaw

U-N1 (Å) 2.06a 2.06a 2.06 U-N2 (Å) 2.06a 2.06a 2.06 U-Li (Å) 2.83 2.85 2.85

Li1-N1i (Å) 1.99 2.36 1.99 Li1-N2 (Å) 2.02 2.38 1.99

N1-U-N1i (º) 90a 109.5a 114.5 N2-U-N2i (º) 90a 109.5a 160.8 N1-U-N2 (º) 90a 109.5a 102.2 N1-U-N2i (º) 90a 109.5a 88.2

a these values were not optimized

S27

Supplementary Table 5. Calculated bond metrics of 2-Na at different geometry and (Et2O-Na)2U(NDIPP)4(THF) at PBE/ZORA/TZ2P level of theory, and comparison with experiment.

Na2U(NDIPP)4 (Et2O-Na)2 U(NDIPP)4(THF)

Experimental Calculated stereo-isomers square-

plane tetrahedron pseudo-seesaw pseudo-seesaw

U-Neq (Å) 2.084(2), 2.063(2) 2.06a 2.06a 2.05 2.08

U-Nax (Å) 2.059(2), 2.068(2) 2.06a 2.06a 2.06 2.09

U-Na (Å) 2.3501(14) 3.3198(12) 3.39 3.21 3.30 3.37

Na-Neqi (Å) 2.402(3), 2.394(3) 2.49 2.63 2.41 2.42

Na-Nax (Å) 2.438(3), 2.452(3) 2.35 2.63 2.42 2.45

Neq-U-Neqi (º) 112.40(10) 90a 109.5a 112.4 121.1

Nax-U-Naxi (º) 163.01(10) 90a 109.5a 156.5 165.0

Neq-U-Nax (º) 91.93(10), 92.61(10) 90a 109.5a 99.7 91.5

Neq-U-Naxi (º) 96.23(10), 98.03(10) 90a 109.5a 93.4 96.0


Supplementary Table 6. Calculated bond metrics of 2-K at different geometry at PBE/ZORA/TZ2P level of theory, and comparison with experiment

K2U(NDIPP)4

Experimental Calculated

stereo-isomers square-plane tetrahedron pseudo-seesaw

U-Neq (Å) 2.074(10), 2.024(11)

2.06a 2.06a 2.06

U-Nax (Å) 2.066(9), 2.046(9)

2.06a 2.06a 2.06

U-K1(Å) 3.765(3), 3.768(3)

3.78 3.72 3.71

K1-Neqi (Å) 2.870(10), 2.867(9)

2.74 3.05 2.77

K1-Nax (Å) 2.888(10), 2.886(9)

2.75 3.02 2.76

Neq-U-Neqi (º) 122.9(4) 90a 109.5a 117.5 Nax-U-Naxi (º) 141.8(4) 90a 109.5a 155.2 Neq-U-Nax (º) 99.6(4), 98.4(4) 90a 109.5a 98.4 Neq-U-Naxi (º) 100.1(4), 97.9(4) 90a 109.5a 94.3


S28

Supplementary Table 7. Calculated bond metrics of 2-Rb at different geometry and (Ph-Rb)2U(NDIPP)4 at PBE/ZORA/TZ2P level of theory, and comparison with experiment.

Rb2U(NDIPP)4 (Ph-Rb)2U(NDIPP)4


stereo-isomers square-


U-Neq (Å) 2.037(3), 2.052(3) 2.06a 2.06a 2.06 2.07

U-Nax (Å) 2.034(3), 2.039(3) 2.06a 2.06a 2.06 2.07

U-Rb(Å) 4.0503(4), 3.9907(4) 3.98 4.41 3.93 4.00

Rb-Neqi (Å) 3.005(3), 3.105(3) 2.93 3.66 2.96 3.03

Rb-Nax (Å) 3.220(3), 3.062(3) 2.92 3.62 2.96 2.99

Neq-U-Neqi (º) 117.65(10) 90a 109.5a 120.4 120.7 Nax-U-Naxi (º) 146.18(11) 90a 109.5a 153.4 151.4

Neq-U-Nax (º) 98.85(11), 100.04(10) 90a 109.5a 98.3 99.4

Neq-U-Naxi (º) 98.97(11), 96.77(11) 90a 109.5a 94.9 94.9


Supplementary Table 8. Calculated bond metrics of 2-Cs at different geometry and (Ph-Cs)2U(NDIPP)4 at PBE/ZORA/TZ2P level of theory, and comparison with experiment.

Cs2U(NDIPP)4 (Ph-Cs)2U(NDIPP)4


stereo-isomers square-


U-Neq (Å) 2.050(4) 2.06a 2.06a 2.06 2.07 U-Nax (Å) 2.075(4) 2.06a 2.06a 2.06 2.07 U-Cs1(Å) 4.1476(3) 4.21 4.42 4.11 4.14

Cs1-Neqi (Å) 3.108(4) 3.11 3.63 3.12 3.14 Cs1-Nax (Å) 3.247(5) 3.12 3.64 3.12 3.20

Neq-U-Neqi (º) 119.1(2) 90a 109.5a 121.2 121.6 Nax-U-Naxi (º) 152.4(2) 90a 109.5a 152.5 149.6 Neq-U-Nax (º) 98.56(18) 90a 109.5a 98.0 99.0 Neq-U-Naxi (º) 95.35(18) 90a 109.5a 95.4 95.8 a these values were not optimized

S29

Supplementary Table 9. Comparison of the calculated bond lengths and bond orders of 2-Li to 2-Cs at PBE/ZORA/TZ2P level of theory. U-N Bond Order U-N Bond Length

(Å) Nalewajski-Mrozek Index

21 Gophinatan-Jug Bond Order

22 2-Li 2.06 2.00 1.83 2-Na 2.06 2.00 1.83 2-K 2.06 1.99 1.82 2-Rb 2.06 1.98 1.81 2-Cs 2.06 1.98 1.81 Supplementary Table 10. Calculated bond metrics for UO4

2-, U(NMe)42-, U(NPh)4

2-, U(NDIPP)42-,

Na2UO4, Na2U(NPh)4, and 2-Li – 2-Cs at PBE-D3/ZORA/TZ2P level of theory.

Molecule Symmetry Distance (Å) Angle (º) U=E Eax-U-Eax Eeq-U-Eeq Eax-U-Eeq

UO42- Td 1.99 109.5 109.5 109.5

U(NH)42- Td 2.07 109.5 109.5 109.5

U(NMe)42- Td 2.08 109.5 109.4 109.5,109.4

U(NPh)42- Pseudo- Td 2.07 111.6 109.9 108.3, 108.4

U(NDIPP)42- Pseudo-C2v 2.07, 2.06 117.3 117.2 103.7, 100.4

Na2UO4 C2v 1.95 166.8 166.8 95.1, 86.4 Na2U(NPh)4 Pseudo- C2v 2.07, 2.08 158.4 100.0 97.4, 96.5

2-Li Pseudo- C2v 2.05 166.9 111.1 99.7,87.7 2-Na Pseudo- C2v 2.05 160.5 113.2 97.3,93.4 2-K Pseudo- C2v 2.04, 2.05 159.6 115.7 96.8, 93.5

2-Rb Pseudo-C2v 2.05 157.4 117.9 97.3,94.3 2-Cs Pseudo-C2v 2.05 156.6 118.4 96.9.95.0

Supplementary Table 11. Calculated bond metrics for UO4

2-, U(NMe)42-, U(NPh)4

2-, U(NDIPP)42-,

Na2UO4, Na2U(NPh)4, and 2-Na at M06-L/ZORA/TZ2P level of theory.

Molecule Symmetry Distance (Å) Angle (º) U=E Eax-U-Eax Eeq-U-Eeq Eax-U-Eeq

UO42- Td 1.99 109.5 109.5 109.5

U(NH)42- Td 2.08 109.5 109.5 109.5

U(NMe)42- Td 2.08 109.5 109.4 109.5,109.2

U(NPh)42- Pseudo- Td 2.08 110.3 109.0 109.6, 109.2

U(NDIPP)42- Pseudo-C2v 2.06, 2.07 119.2 114.2 106.1, 105.6

Na2UO4 C2v 1.94 172.7 173.5 94.5, 85.9 Na2U(NPh)4 Pseudo- C2v 2.06, 2.08 143.4 98.7 109.8, 94.0

2-Na Pseudo- C2v 2.05, 2.06 156.8 112.2 101.3, 91.7

S30

Supplementary Table 12. Calculated bond metrics of U(NDIPP)42- anion complex with DFT

functionals PBE, PBE-D3, and M06-L with ZORA/TZ2P method, and comparison with experiment.

U(NDIPP)42-

Experimental Calculated DFT functional PBE PBE-D3 M06-L

U-Neq (Å) 2.060(3) 2.07 2.06 2.06 U-Nax (Å) 2.064(3) 2.07 2.07 2.07

Neq-U-Neqi (º) 113.95(17) 123.7 117.2 114.2 Nax-U-Naxi (º) 122.37(17) 123.8 117.3 119.2 Neq-U-Nax (º) 105.17(12) 104.1 103.7 106.1 Neq-U-Naxi (º) 105.29(12) 101.4 100.4 105.6 Supplementary Table 13. Topological properties obtained from Atoms in Molecules (AIM) analysis to support the bond order analysis. Note that a higher density, ρ, at bond critical point corresponds to greater covalency, and a non-zero ellipticity value suggests double bond.

Bond Critical Point Bond RU-N (Å) ρ Ellipticity

2-Li Equatorial 2.06 0.147 0.18

Axial 2.06 0.146 0.10 2-Na

Equatorial 2.05 0.148 0.16 Axial 2.06 0.147 0.09

2-K Equatorial 2.06 0.148 0.18

Axial 2.06 0.147 0.10 2-Rb

Equatorial 2.06 0.146 0.19 Axial 2.06 0.146 0.10

2-Cs Equatorial 2.06 0.146 0.20

Axial 2.06 0.146 0.10

S31

Supplementary Table 14. Percentage Atomic Orbital Contributions to natural bond orbitals (NBOs). The first line lists occupancy number; NBO label (type BD for 2-center bond); serial number (1 for single bond and 2 for double bond between the pair of atoms); and the atoms to which the NBO is affixed. The next lines summarize the natural atomic hybrids hA of which the NBO is composed, giving the percentage of the NBO on each hybrid, the polarization coefficient cA, the atom label, hybrid label of each hA and the percentage. a. Li2U(NDIPP)4

1. (1.93351) BD ( 1) U 1 - N 3 ( 24.65%) 0.4965* U 1 s( 0.29%)p 6.83( 1.95%)d99.99( 46.33%) f99.99( 51.42%)g 0.06( 0.02%) ( 75.35%) 0.8680* N 3 s( 0.40%)p99.99( 99.59%)d 0.03( 0.01%) 2. (1.79187) BD ( 2) U 1 - N 3 ( 20.17%) 0.4491* U 1 s( 0.19%)p 5.80( 1.08%)d99.99( 29.26%) f99.99( 69.45%)g 0.10( 0.02%) ( 79.83%) 0.8935* N 3 s( 0.59%)p99.99( 99.40%)d 0.02( 0.01%) 3. (1.94228) BD ( 1) U 1 - N 4 ( 24.06%) 0.4905* U 1 s( 0.04%)p49.87( 1.78%)d99.99( 38.22%) f99.99( 59.95%)g 0.44( 0.02%) ( 75.94%) 0.8715* N 4 s( 0.21%)p99.99( 99.78%)d 0.06( 0.01%) 4. (1.79789) BD ( 2) U 1 - N 4 ( 20.72%) 0.4552* U 1 s( 0.14%)p 2.69( 0.39%)d99.99( 29.60%) f99.99( 69.85%)g 0.14( 0.02%) ( 79.28%) 0.8904* N 4 s( 0.02%)p99.99( 99.97%)d 0.60( 0.01%) 5. (1.93351) BD ( 1) U 1 - N 64 ( 24.65%) 0.4965* U 1 s( 0.29%)p 6.83( 1.95%)d99.99( 46.33%) f99.99( 51.42%)g 0.06( 0.02%) ( 75.35%) 0.8680* N 64 s( 0.40%)p99.99( 99.59%)d 0.03( 0.01%) 6. (1.79187) BD ( 2) U 1 - N 64 ( 20.17%) 0.4491* U 1 s( 0.19%)p 5.80( 1.08%)d99.99( 29.26%) f99.99( 69.45%)g 0.10( 0.02%) ( 79.83%) 0.8935* N 64 s( 0.59%)p99.99( 99.40%)d 0.02( 0.01%) 7. (1.94228) BD ( 1) U 1 - N 65 ( 24.06%) 0.4905* U 1 s( 0.04%)p49.87( 1.78%)d99.99( 38.22%) f99.99( 59.95%)g 0.44( 0.02%) ( 75.94%) 0.8715* N 65 s( 0.21%)p99.99( 99.78%)d 0.06( 0.01%) 8. (1.79789) BD ( 2) U 1 - N 65 ( 20.72%) 0.4552* U 1 s( 0.14%)p 2.69( 0.39%)d99.99( 29.60%) f99.99( 69.85%)g 0.14( 0.02%) ( 79.28%) 0.8904* N 65 s( 0.02%)p99.99( 99.97%)d 0.60( 0.01%)

b. Na2U(NDIPP)4 1. (1.93412) BD ( 1) U 1 - N 3 ( 24.68%) 0.4968* U 1 s( 0.24%)p10.16( 2.44%)d99.99( 43.22%) f99.99( 54.08%)g 0.06( 0.01%) ( 75.32%) 0.8679* N 3 s( 0.45%)p99.99( 99.54%)d 0.02( 0.01%) 2. (1.77490) BD ( 2) U 1 - N 3 ( 21.23%) 0.4608* U 1 s( 0.03%)p99.99( 2.82%)d99.99( 30.95%) f99.99( 66.19%)g 0.55( 0.01%) ( 78.77%) 0.8875* N 3 s( 0.04%)p99.99( 99.95%)d 0.18( 0.01%) 3. (1.94458) BD ( 1) U 1 - N 4 ( 24.46%) 0.4945* U 1 s( 0.13%)p20.07( 2.54%)d99.99( 33.69%) f99.99( 63.64%)g 0.11( 0.01%) ( 75.54%) 0.8692* N 4 s( 0.46%)p99.99( 99.53%)d 0.01( 0.01%) 4. (1.79163) BD ( 2) U 1 - N 4 ( 21.80%) 0.4669* U 1 s( 0.19%)p 7.92( 1.48%)d99.99( 31.02%) f99.99( 67.30%)g 0.08( 0.02%) ( 78.20%) 0.8843* N 4 s( 0.01%)p99.99( 99.99%)d 0.31( 0.00%) 5. (1.93412) BD ( 1) U 1 - N 64 ( 24.68%) 0.4968* U 1 s( 0.24%)p10.16( 2.44%)d99.99( 43.22%) f99.99( 54.08%)g 0.06( 0.01%) ( 75.32%) 0.8679* N 64 s( 0.45%)p99.99( 99.54%)d 0.02( 0.01%) 6. (1.77490) BD ( 2) U 1 - N 64 ( 21.23%) 0.4608* U 1 s( 0.03%)p99.99( 2.82%)d99.99( 30.95%) f99.99( 66.19%)g 0.55( 0.01%) ( 78.77%) 0.8875* N 64 s( 0.04%)p99.99( 99.95%)d 0.18( 0.01%) 7. (1.94458) BD ( 1) U 1 - N 65 ( 24.46%) 0.4945* U 1 s( 0.13%)p20.07( 2.54%)d99.99( 33.69%) f99.99( 63.64%)g 0.11( 0.01%) ( 75.54%) 0.8692* N 65 s( 0.46%)p99.99( 99.53%)d 0.01( 0.01%) 8. (1.79163) BD ( 2) U 1 - N 65 ( 21.80%) 0.4669* U 1 s( 0.19%)p 7.92( 1.48%)d99.99( 31.02%) f99.99( 67.30%)g 0.08( 0.02%) ( 78.20%) 0.8843* N 65 s( 0.01%)p99.99( 99.99%)d 0.31( 0.00%)

S32

c. K2U(NDIPP)4 1. (1.92729) BD ( 1) U 1 - N 3 ( 24.35%) 0.4935* U 1 s( 0.23%)p 8.99( 2.10%)d99.99( 47.20%) f99.99( 50.45%)g 0.07( 0.02%) ( 75.65%) 0.8698* N 3 s( 0.70%)p99.99( 99.30%)d 0.01( 0.01%) 2. (1.75264) BD ( 2) U 1 - N 3 ( 20.74%) 0.4554* U 1 s( 0.01%)p99.99( 1.70%)d99.99( 30.02%) f99.99( 68.25%)g 0.94( 0.01%) ( 79.26%) 0.8903* N 3 s( 0.10%)p99.99( 99.90%)d 0.06( 0.01%) 3. (1.94133) BD ( 1) U 1 - N 4 ( 24.43%) 0.4943* U 1 s( 0.06%)p35.63( 1.98%)d99.99( 33.70%) f99.99( 64.25%)g 0.27( 0.02%) ( 75.57%) 0.8693* N 4 s( 0.54%)p99.99( 99.46%)d 0.01( 0.00%) 4. (1.77711) BD ( 2) U 1 - N 4 ( 21.35%) 0.4620* U 1 s( 0.08%)p12.32( 1.03%)d99.99( 30.28%) f99.99( 68.59%)g 0.19( 0.02%) ( 78.65%) 0.8869* N 4 s( 0.01%)p99.99( 99.99%)d 0.14( 0.00%) 5. (1.92729) BD ( 1) U 1 - N 64 ( 24.35%) 0.4935* U 1 s( 0.23%)p 8.99( 2.10%)d99.99( 47.20%) f99.99( 50.45%)g 0.07( 0.02%) ( 75.65%) 0.8698* N 64 s( 0.70%)p99.99( 99.30%)d 0.01( 0.01%) 6. (1.75264) BD ( 2) U 1 - N 64 ( 20.74%) 0.4554* U 1 s( 0.01%)p99.99( 1.70%)d99.99( 30.02%) f99.99( 68.25%)g 0.94( 0.01%) ( 79.26%) 0.8903* N 64 s( 0.10%)p99.99( 99.90%)d 0.06( 0.01%) 7. (1.94133) BD ( 1) U 1 - N 65 ( 24.43%) 0.4943* U 1 s( 0.06%)p35.63( 1.98%)d99.99( 33.70%) f99.99( 64.25%)g 0.27( 0.02%) ( 75.57%) 0.8693* N 65 s( 0.54%)p99.99( 99.46%)d 0.01( 0.00%) 8. (1.77711) BD ( 2) U 1 - N 65 ( 21.35%) 0.4620* U 1 s( 0.08%)p12.32( 1.03%)d99.99( 30.28%) f99.99( 68.59%)g 0.19( 0.02%) ( 78.65%) 0.8869* N 65 s( 0.01%)p99.99( 99.99%)d 0.14( 0.00%)

d. Rb2U(NDIPP)4

1. (1.92341) BD ( 1) U 1 - N 2 ( 24.06%) 0.4905* U 1 s( 0.20%)p10.49( 2.06%)d99.99( 48.88%) f99.99( 48.84%)g 0.10( 0.02%) ( 75.94%) 0.8714* N 2 s( 0.84%)p99.99( 99.16%)d 0.01( 0.01%) 2. (1.74785) BD ( 2) U 1 - N 2 ( 20.74%) 0.4554* U 1 s( 0.01%)p99.99( 1.65%)d99.99( 30.08%) f99.99( 68.24%)g 1.03( 0.01%) ( 79.26%) 0.8903* N 2 s( 0.11%)p99.99( 99.89%)d 0.04( 0.00%) 3. (1.93868) BD ( 1) U 1 - N 3 ( 24.30%) 0.4929* U 1 s( 0.04%)p42.12( 1.88%)d99.99( 33.56%) f99.99( 64.51%)g 0.35( 0.02%) ( 75.70%) 0.8701* N 3 s( 0.50%)p99.99( 99.50%)d 0.01( 0.00%) 4. (1.77040) BD ( 2) U 1 - N 3 ( 21.28%) 0.4613* U 1 s( 0.07%)p15.07( 1.05%)d99.99( 29.45%) f99.99( 69.42%)g 0.22( 0.02%) ( 78.72%) 0.8872* N 3 s( 0.00%)p 1.00(100.00%)d 0.00( 0.00%) 5. (1.92341) BD ( 1) U 1 - N 62 ( 24.06%) 0.4905* U 1 s( 0.20%)p10.49( 2.06%)d99.99( 48.88%) f99.99( 48.84%)g 0.10( 0.02%) ( 75.94%) 0.8714* N 62 s( 0.84%)p99.99( 99.16%)d 0.01( 0.01%) 6. (1.74785) BD ( 2) U 1 - N 62 ( 20.74%) 0.4554* U 1 s( 0.01%)p99.99( 1.65%)d99.99( 30.08%) f99.99( 68.24%)g 1.03( 0.01%) ( 79.26%) 0.8903* N 62 s( 0.11%)p99.99( 99.89%)d 0.04( 0.00%) 7. (1.93868) BD ( 1) U 1 - N 63 ( 24.30%) 0.4929* U 1 s( 0.04%)p42.12( 1.88%)d99.99( 33.56%) f99.99( 64.51%)g 0.35( 0.02%) ( 75.70%) 0.8701* N 63 s( 0.50%)p99.99( 99.50%)d 0.01( 0.00%) 8. (1.77040) BD ( 2) U 1 - N 63 ( 21.28%) 0.4613* U 1 s( 0.07%)p15.07( 1.05%)d99.99( 29.45%) f99.99( 69.42%)g 0.22( 0.02%) ( 78.72%) 0.8872* N 63 s( 0.00%)p 1.00(100.00%)d 0.00( 0.00%)

S33

e. Cs2U(NDIPP)4 1. (1.92213) BD ( 1) U 1 - N 3 ( 24.02%) 0.4901* U 1 s( 0.22%)p 9.28( 2.04%)d99.99( 49.30%) f99.99( 48.42%)g 0.09( 0.02%) ( 75.98%) 0.8716* N 3 s( 0.86%)p99.99( 99.14%)d 0.01( 0.01%) 2. (1.74326) BD ( 2) U 1 - N 3 ( 20.65%) 0.4544* U 1 s( 0.02%)p71.50( 1.33%)d99.99( 30.18%) f99.99( 68.45%)g 0.73( 0.01%) ( 79.35%) 0.8908* N 3 s( 0.09%)p99.99( 99.90%)d 0.04( 0.00%) 3. (1.93761) BD ( 1) U 1 - N 4 ( 24.29%) 0.4928* U 1 s( 0.04%)p43.56( 1.79%)d99.99( 33.43%) f99.99( 64.73%)g 0.39( 0.02%) ( 75.71%) 0.8701* N 4 s( 0.51%)p99.99( 99.49%)d 0.01( 0.00%) 4. (1.76656) BD ( 2) U 1 - N 4 ( 21.20%) 0.4605* U 1 s( 0.05%)p16.64( 0.88%)d99.99( 29.49%) f99.99( 69.56%)g 0.29( 0.02%) ( 78.80%) 0.8877* N 4 s( 0.00%)p 1.00(100.00%)d 0.00( 0.00%) 5. (1.92213) BD ( 1) U 1 - N 64 ( 24.02%) 0.4901* U 1 s( 0.22%)p 9.28( 2.04%)d99.99( 49.30%) f99.99( 48.42%)g 0.09( 0.02%) ( 75.98%) 0.8716* N 64 s( 0.86%)p99.99( 99.14%)d 0.01( 0.01%) 6. (1.74326) BD ( 2) U 1 - N 64 ( 20.65%) 0.4544* U 1 s( 0.02%)p71.50( 1.33%)d99.99( 30.18%) f99.99( 68.45%)g 0.73( 0.01%) ( 79.35%) 0.8908* N 64 s( 0.09%)p99.99( 99.90%)d 0.04( 0.00%) 7. (1.93761) BD ( 1) U 1 - N 65 ( 24.29%) 0.4928* U 1 s( 0.04%)p43.56( 1.79%)d99.99( 33.43%) f99.99( 64.73%)g 0.39( 0.02%) ( 75.71%) 0.8701* N 65 s( 0.51%)p99.99( 99.49%)d 0.01( 0.00%) 8. (1.76656) BD ( 2) U 1 - N 65 ( 21.20%) 0.4605* U 1 s( 0.05%)p16.64( 0.88%)d99.99( 29.49%) f99.99( 69.56%)g 0.29( 0.02%) ( 78.80%) 0.8877* N 65 s( 0.00%)p 1.00(100.00%)d 0.00( 0.00%)

S34

VI. X-ray Structural Determination

General Procedures. Data were collected using either a Nonius Kappa CCD diffractometer with

Mo-Ka radiation (l = 0.71073 Å) at Purdue University, or a Bruker AXS X8 Prospector CCD

diffractometer with Cu-Ka radiation (l = 1.54184 Å) at Youngstown State University. The

KappaCCD instrument features a fine focus sealed tube X-ray source with graphite

monochromator. The Prospector CCD instrument is equipped with an IµS microsource with a

laterally graded multilayer (Goebel) mirror for monochromatization. Single crystals were mounted

on Mitegen micromesh or loop mounts using a trace of mineral oil and cooled in-situ to 150(2) or

100(2) K for data collection. Data on the KappaCCD instrument were collected using the Nonius

Collect software,23 and processed using HKL3000.24 Data were corrected for absorption and

scaled using Scalepack.24 Data on the Bruker Prospector instrument were collected, reflections

were indexed and processed, and the files scaled and corrected for absorption using APEX2.25

The space groups were assigned and the structures were solved by direct methods using XPREP

within the SHELXTL suite of programs26,27 and refined by full matrix least squares against F2 with

all reflections using Shelxl 2013 or 201428,29 using the graphical interface Shelxle.30 H atoms were

positioned geometrically and constrained to ride on their parent atoms, with carbon hydrogen

bond distances of 0.95 Å for and aromatic C-H, and 1.00, 0.99 and 0.98 Å for aliphatic C-H, CH2

and CH3 moieties, respectively. Methyl H atoms were allowed to rotate but not to tip to best fit the

experimental electron density. Uiso(H) values were set to a multiple of Ueq(C) with 1.5 for CH3, and

1.2 for C-H and CH2 units, respectively.

In (2-Rb) three coordinated THF molecules were refined as disordered over each two mutually

exclusive positions. The geometries of all THF rings were restrained to be similar, and Uij

components of ADPs were restrained to be similar for atoms closer than 1.7 Å. Subject to these

conditions the occupancy rates refined to 0.404(19) to 0.596(19), 0.45(2) to 0.55(2), and 0.417(9)

to 0.583(9).

No A or B alerts for this structure

In (2-Na) a coordinated THF molecule was refined as disordered over two mutually exclusive

orientations. The geometries of the THF rings were restrained to be similar, and Uij components

of ADPs were restrained to be similar for atoms closer than 1.7 Å. Subject to these conditions the

occupancy rates refined to 0.387(12) to 0.613(12).


S35

In (2-Cs) A toluene molecule is 1:1 disordered across a twofold axis. The benzene ring was

constrained to resemble an ideal hexagon with 1.39 Å C-C bonds. The ethyl C atom was

restrained to lie in plane with the other atoms, and to be symmetric with respect to the two ortho

C atoms. The carbon atoms were subjected to a rigid bond restraint (RIGU). One isopropyl group

was refined as disordered by slight rotation. Its C-C bonds were restrained to be similar in length.

The carbon atoms were subjected to a rigid bond restraint for each moiety (RIGU), and the Uij

components of ADPs of all disordered isopropyl C atoms were restrained to be similar if closer

than 1.7 Å. Subject to these conditions the occupancy ratio refined to 0.626(19) to 0.374(19).


In (2-K(crypt)) an outer sphere THF molecule is disordered over a C2 rotational axis. Chemically

equivalent bond distances and angles were restrained to be similar (using SADI commands for

Shelxl). A rigid bond restraint was applied to the disordered atoms (RIGU command in Shelxl).


For (2-K) The molecules possess pseudo-symmetry due to orientations of di-iso-propylphenyl

substituents. Six coordinated THF molecules, as well as one co-crystallized THF, were refined as

disordered over each two mutually exclusive positions. The geometries disordered pairs of THF

rings were restrained to be similar, and Uij components of ADPs were restrained to be similar for

atoms closer than 1.7 Angstroms. For disordered THF pair O11A and O11B, the carbon atoms

C114 and C150 were constrained to have the same position and ADPs. The distance between

Three of the disordered THF molecules coordinated to potassium ions were constrained to be the

same. Subject to these conditions, the occupancies for THF molecules containing O1, O2, O4,

O11, O12, O14, and O15 respectively refined to 0.865(12) to 0.135(12), 0.66(4) to 0.34(4),

0.597(14) to 0.603(14), 0.903(16) to 0.097(16), 0.73(3) to 0.27(3), 0.62(2) to 0.38(2), and 0.56(2)

to 0.46(2).

PLAT234_ALERT_4_B Large Hirshfeld Difference C121 -- C122 .. 0.26 Ang.

Author Response: The atoms belong mostly to entities with large libration and (possibly)

unresolved minor disorder, such as ill defined THF molecules.

PLAT342_ALERT_3_B Low Bond Precision on C-C Bonds ............... 0.02049 Ang.

Author Response: The structure features a large number of THF molecules and isopropyl

moieties with large thermal libration. Many of the THF molecules are also disordered. The

accuracy for the THF and isopropyl C-C bonds is low, causing an on average low C-C bond

precision.

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Complete crystallographic data, in CIF format, have been deposited with the Cambridge

Crystallographic Data Centre. CCDC 1473108 (2-Na), 1473109 (2-Rb), 1473110 (2-Cs), 1489218

(2-K(crypt)) and 1506789 (2-K) contains the supplementary crystallographic data for this paper.

These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via

www.ccdc.cam.ac.uk/data_request/cif.

The Prospector X-ray diffractometer was funded by NSF Grant DMR 1337296.

Supplementary Fig. 19. X-ray crystal structure of 2-Rb depicting the interaction between two molecules of 2-Rb in the solid state.

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Supplementary Fig. 20. X-ray crystal structure of 2-Cs depicting the interaction between two molecules of 2-Cs in the solid state.

Supplementary Fig. 21. X-ray crystal structure of 2-K(crypt) with two molecules of 2.2.2-Cryptand(K) included.

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Supplementary Fig. 22. X-ray crystal structure of 2-Cs with thermal ellipsoids depicted at 30% probability.

Supplementary Fig. 23. X-ray crystal structure of 2-Na with thermal ellipsoids depicted at 30% probability

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Supplementary Fig. 24. X-ray crystal structure of 2-Rb with thermal ellipsoids depicted at 30% probability.

Supplementary Fig. 25. X-ray crystal structure of 2-K(crypt) with thermal ellipsoids depicted at 30% probability.

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Supplementary Fig. 26. X-ray crystal structure of 2-K with thermal ellipsoids depicted at 30% probability. Co-crystalized THF solvent molecules, hydrogen atoms, and another assymetric 2-K molecule have been omitted for clarity.

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Supplementary Table 15. Crystallographic experimental for [Na]2[U(NDIPP)4] (2-Na)

Crystal data Chemical formula C60H95N4Na2O3U

Mr 1204.40 Crystal system,

space group Monoclinic, P21/n

Temperature (K) 150 a, b, c (Å) 14.7552 (2), 20.6750 (5), 20.3540 (3)

β (°) 105.139 (1) V (Å3) 5993.77 (19)

Z 4 Radiation type Mo Ka

µ (mm-1) 2.77 Crystal size (mm) 0.70 × 0.70 × 0.60

Data collection

Diffractometer Nonius KappaCCD diffractometer

Absorption correction

Multi-scan SCALEPACK (Otwinowski & Minor, 1997)

Tmin, Tmax 0.023, 0.190 No. of measured, independent and

observed [I > 2s(I)] reflections

22899, 14103, 10407

Rint 0.056

(sin q/l)max (Å-1) 0.666

Refinement

R[F2 > 2s(F2)], wR(F2), S

0.033, 0.065, 1.0

No. of reflections 14103 No. of parameters 697 No. of restraints 160

H-atom treatment H-atom parameters constrained

Dρmax, Dρmin (e Å-3) 0.71, -0.75

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Supplementary Table 16. Crystallographic experimental for [Rb]2[U(NDIPP)4] (2-Rb)

Crystal data

Chemical formula C65H104N4O3Rb2U Mr 1398.49

Crystal system, space group Monoclinic, P21/c


β (°) 95.877 (1) V (Å3) 6752.97 (16)

Z 4

Radiation type Mo Ka µ (mm-1) 3.88

Crystal size (mm) 0.50 × 0.50 × 0.40

Data collection

Diffractometer Nonius KappaCCD diffractometer





16203, 1623, 11005

Rint 0.029

(sin q/l)max (Å-1) 0.666

Refinement

R[F2 > 2s(F2)], wR(F2), S 0.038, 0.068, 0.97



Dρmax, Dρmin (e Å-3) 0.94, -0.71

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Supplementary Table 17. Crystallographic experimental for [Cs]2[U(NDIPP)4] (2-Cs)

Crystal data

Chemical formula C48H68Cs2N4U·C7H8 Mr 1297.04

Crystal system, space group Tetragonal, P43212

Temperature (K) 100 a, c (Å) 16.9084 (5), 18.7777 (7) V (Å3) 5368.4 (4)

Z 4

Radiation type Cu Ka µ (mm-1) 19.20

Crystal size (mm) 0.15 × 0.10 × 0.04

Data collection

Diffractometer Bruker AXS X8 Prospector CCD diffractometer


Multi-scan Apex2 v2014.11 (Bruker, 2014)



32133, 4736, 4557

Rint 0.048

(sin q/l)max (Å-1) 0.597

Refinement

R[F2 > 2s(F2)], wR(F2), S 0.021, 0.050, 1.04



Dρmax, Dρmin (e Å-3) 1.00, -0.39

Absolute structure Flack x determined using 1882 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).

Absolute structure parameter -0.023 (4)

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Supplementary Table 18. Crystallographic experimental for [(Crypt-K)]2[U(NDIPP)4] (2-K(crypt))

Crystal data

Chemical formula C48H68N4U·2(C18H36KN2O6)·C4H8 Mr 1842.37

Crystal system, space group Monoclinic, C2/c


β (°) 111.50 (3) V (Å3) 9318(4)

Z 4 Radiation type Mo Kα

µ (mm-1) 1.89 Crystal size (mm) 0.25 x 0.25 x 0.10

Data collection

Diffractometer Nonius Kappa CCD diffractometer Absorption correction Multi-scan SCALEPACK (Otwinowski & Minor, 1997)



42111, 12428, 9517

Rint 0.055

(sin q/l)max (Å-1) 0.719

Refinement

R[F2 > 2s(F2)], wR(F2), S 0.047, 0.092, 1.14



Dρmax, Dρmin (e Å-3) 1.94, -2.71

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Supplementary Table 19. Crystallographic experimental for [K]2[U(NDIPP)4] (2-K)

Crystal data

Chemical formula C64H99K2N4O4U·C64H99K2N4O4U·C4H8O·C4H8O Mr 1376.80

Crystal system, space group

Monoclinic, P21/c


β (°) 96.572 (5) V (Å3) 13693.2 (15)

Z 8 Radiation type Cu Ka

µ (mm-1) 8.13 Crystal size (mm) 0.31 × 0.28 × 0.06

Data collection

Diffractometer Rigaku Rapid II curved image plate diffractometer Absorption correction




153402, 22140, 10784

Rint 0.115

(sin q/l)max (Å-1) 0.581

Refinement

R[F2 > 2s(F2)], wR(F2), S

0.086, 0.297, 1.05



Dρmax, Dρmin (e Å-3) 2.05, -1.80

S46

VII. References.

1 Pangborn, A. B., Giardello, M. A., Grubbs, R. H., Rosen, R. K. & Timmers, F. J. Safe and convenient procedure for solvent purification. Organometallics 15, 1518-1520, (1996).

2 Barral, K., Moorhouse, A. D. & Moses, J. E. Efficient conversion of aromatic amines into azides: A one-pot synthesis of triazole linkages. Org. Lett. 9, 1809-1811, (2007).

3 Anderson, N. H. et al. Investigation of uranium tris(imido) complexes: Synthesis, characterization, and reduction chemistry of [U(NDIPP)3(thf)3]. Angew. Chem. Int. Ed. 54, 9386-9389, (2015).

4 Clark, D. L. & Sattelberger, A. P. Lewis base adducts of uranium triiodide and tris[bis(trimethylsilyl)amido]uranium. Inorg. Synth. 31, 307-315, (1997).

5 Chakraborty, S., Chattopadhyay, J., Guo, W. & Billups, W. E. Functionalization of potassium graphite. Angew. Chem., Int. Ed. 46, 4486-4488, (2007).

6 ADF2013, SCM, Theoretical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands, http://www.scm.com/.

7 van Lenthe, E., Snijders, J. G. & Baerends, E. J. The zero-order regular approximation for relativistic effects: The effect of spin–orbit coupling in closed shell molecules. J. Chem. Phys. 105, 6505-6516, (1996).

8 Anderson, N. H. et al. Harnessing redox activity for the formation of uranium tris(imido) compounds. Nature Chem. 6, 919-926, (2014).

9 Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865-3868, (1996).

10 Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple [Phys. Rev. Lett. 77, 3865 (1996)]. Phys.l Rev. Lett. 78, 1396-1396, (1997).

11 Grimme, S., Antony, J., Ehrlich, S. & Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 132, 154104, (2010).

12 Zhao, Y. & Truhlar, D. G. A new local density functional for main-group thermochemistry, transition metal bonding, thermochemical kinetics, and noncovalent interactions. J. Chem. Phys. 125, 194101, (2006).

13 Gaussian 09, Revision E.01 (Gaussian, Inc., Wallingford CT, 2009). 14 Roos, B. O., Taylor, P. R. & Si≐gbahn, P. E. M. A complete active space SCF method

(CASSCF) using a density matrix formulated super-CI approach. Chem. Phys. 48, 157-173, (1980).

15 Aquilante, F. et al. Molcas 8: New capabilities for multiconfigurational quantum chemical calculations across the periodic table. J. Comp. Chem. 37, 506-541, (2016).

16 Roos, B. O., Lindh, R., Malmqvist, P.-Å., Veryazov, V. & Widmark, P.-O. New relativistic ANO basis sets for actinide atoms. Chem. Phys. Lett. 409, 295-299, (2005).

17 Douglas, M. & Kroll, N. M. Quantum electrodynamical corrections to the fine structure of helium. Annals of Physics 82, 89-155, (1974).

18 Hess, B. A. Applicability of the no-pair equation with free-particle projection operators to atomic and molecular structure calculations. Phys. Rev. A 32, 756-763, (1985).

19 Hess, B. A. Relativistic electronic-structure calculations employing a two-component no-pair formalism with external-field projection operators. Phys. Rev. A 33, 3742-3748, (1986).

20 Bolvin, H., Wahlgren, U., Gropen, O. & Marsden, C. Ab initio study of the two iso-electronic molecules NpO4

- and UO42-. J. Phys. Chem. A 105, 10570-10576, (2001).

21 Nalewajski, R. F., Mrozek, J. & Mazur, G. Quantum chemical valence indices from the one-determinantal difference approach. Can. J. Chem. 74, 1121-1130, (1996).

22 Gopinathan, M. S. & Jug, K. Valency. I. A quantum chemical definition and properties. Theoretica chimica acta 63, 497-509.

23 Nonius. Collect Users Manual, Nonius Delft, The Netherlands. (1998). 24 Otwinowski, Z. & Minor, W. in Methods in Enzymology Vol. Volume 276, 307-326

(Academic Press, 1997).

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25 Apex2 v2013.4-1, v2014.11, v2014.1-1, Saint V8.34A, SAINT V8.30C, Bruker AXS Inc.: Madison (WI), USA, 2013/2014.

26 Sheldrick, G. M. A short history of SHELX Acta. Cryst. 112, A64, (2008). 27 SHELXTL (Version 6.14) (2000-2003) Bruker Advanced X-ray Solutions, Bruker AXS

Inc., Madison, Wisconsin: USA. 28 XS v. 2013/1 (Univeristy of Göttingen, Göttingen, Germany 2013). 29 Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta. Cryst. C, 71, 3-8,

(2015). 30 Hubschle, C. B., Sheldrick, G. M. & Dittrich, B. ShelXle: a Qt graphical user interface for

SHELXL. J. App. Cryst. 44, 1281-1284, (2011).

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In te format proided b te autors and unedited. Elucidating ... · such time, the solution was treated with a single equivalent of LiCH 2TMS (10 mg, 0.102 mmol) slowly, and the solution