SUPPLEMENTARY INFORMATION

Transcription

1 In the format provided by the authors and unedited. SUPPLEMENTARY INFORMATION DOI: /NCHEM.2899 The Role of Uranium Arene Bonding in H 2 O Reduction Catalysis Dominik P. Halter, 1 Frank W. Heinemann, 1 Laurent Maron, 2 and Karsten Meyer 1 * 1 Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander University Erlangen-Nürnberg (FAU), D Erlangen, Germany. 2 Université de Toulouse, INSA, UPS, LPCNO, 135 Avenue de Rangueil, F Toulouse, France, and CNRS, LPCNO, F Toulouse, France Table of Contents General Considerations... 2 Synthetic Procedures... 3 Spectroscopic Details H NMR Spectroscopy... 5 IR Spectroscopy... 8 Vis-NIR Spectroscopy SQUID Magnetometry Electrochemical Studies X-Ray Crystal Structure Determinations X-Ray Crystal Structure Determination Details Spacefilling Models of 1 and 3, Together with Illustration of Their Active Sites for H 2 O Reduction Graphical Representations Theoretical Calculations Optimized Structures of Crytallographically Characterized Complexes Optimized Structures for the Reaction Profile Presented in Figure 6 of the main text References NATURE CHEMISTRY Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

2 General Considerations All air- and moisture-sensitive experiments were performed under dry nitrogen atmosphere using standard Schlenk techniques or in MBraun inert-gas gloveboxes containing an atmosphere of purified dinitrogen. The glovebox is equipped with a 35 C freezer. Solvents were purified using a twocolumn solid-state purification system (Glass Contour System, Irvine, CA), transferred to the glovebox without exposure to air, and stored over molecular sieves and sodium (where appropriate). All glassware was dried by storage in an oven overnight (> 8 h) at a temperature > 150 C. NMR solvents were obtained packaged under argon and stored over activated molecular sieves and sodium (where appropriate) prior to use. [(( Ad,Me ArO) 3 mes)u] (1) and [(( Ad,Me ArO) 3 tacn)u] (3) were prepared according to the literature procedures 1,2. All other reagents were acquired from commercial sources and used as received. 1 H NMR spectra were recorded on a JEOL ECX 400 or a JEOL ECX 270 at a probe temperature of 23 C. Chemical shifts δ, are reported relative to residual 1 H resonances of the solvent in ppm 3. Electronic absorption spectra were recorded from 200 to 2500 nm (Shimadzu, UV-3600) in the indicated solvent at room temperature, and plotted from 400 to 2150 nm to emphasize the f-f transitions. Data points between 1700 and 1745 nm are obscured for all measurements by a switch from the In/Ga/As detector to the PbS detector of the instrument and were thus removed from graphical representations. Infrared (IR) spectra were recorded on a Shimadzu Affinity-1 CE FTIR instrument from 400 to 4000 cm 1. Solid samples of the compounds were homogenized with excess amount of KBr and a pressed pellet was measured at room temperature. X-Band EPR spectra were recorded on a JEOL CW spectrometer, JESFA200, equipped with an X-band Gunn diode oscillator bridge, a cylindrical mode cavity, as well as a nitrogen cryostat (94 K), or a helium cryostat (7 K), respectively. The spectrum was simulated with the program W95EPR 4. Elemental analysis was obtained using Euro EA 3000 (Euro Vector) and EA 1108 (Carlo-Erba) elemental analyzers in the Chair of Inorganic Chemistry at the University Erlangen-Nürnberg (Erlangen, Germany). Electrochemical experiments were carried out using a three-electrode setup with a rotating glassy carbon working electrode (3mm diameter) and platinum rods as counter- and reference electrodes. The potentiostat was a Metrohm µ Autolab Type-III. The entire setup was placed inside a nitrogen-equipped glovebox and only degassed, unstabilized, and dry THF (stored over activated molecular sieves) was used during the experiments. All samples were measured in 0.1 M electrolyte solutions of TBAPF 6 (purchased from Sigma Aldrich and used without purification) in THF. Reported half-wave potentials were referenced to the Fc + /Fc redox couple by adding recrystallized and purified ferrocene to the sample solution. Magnetism data of crystalline powdered samples were recorded with a SQUID magnetometer (Quantum Design) at 10 koe (2 300 K). Values of the magnetic susceptibility were corrected for the underlying diamagnetic increment (χ dia = 652, cm 3 mol 1 for 2, 918, cm 3 mol 1 for 2 K, and cm 3 mol 1 for 4) by using tabulated Pascal constants and the effect of the blank sample holders (gelatin capsule/straw) 5. Samples used for magnetization measurements were checked for chemical composition and purity by C,H,N elemental analysis and 1 H NMR spectroscopy. 2

3 Synthetic Procedures Synthesis of [(( Ad,Me ArO) 3 mes)u(o)(thf)] (2) A solution of [(( Ad,Me ArO) 3 mes)u] (45.0 mg, mol) in benzene (20 ml) was stirred for 30 min. under 1 atm. of N 2 O. The solvent was removed in vacuo to obtain the title compound as a red-brown powder. Crystals suitable for XRD analysis were obtained from a concentrated pentane solution with 2 drops of THF per 5 ml pentane at 35 C. Yield: 91% (44.0 mg, mol) 1 H NMR (400 MHz, benzene-d 6, RT) δh = 0.95 (br. s., 18H), 1.36 (br. s., 4H), 2.62 (br. s., 9 H), 3.31 (br.s., 9 H), 3.49 (br. s., 4H), 3.78 (d, J = 11.0 Hz, 9 H), 3.94 (br. s., 9 H), 5.70 (br.s., 6 H), 6.20 (s, 3 H), 6.31 (s, 6 H), 6.49 (d, J = 11.0 Hz, 9 H) ppm. Elemental Analysis for C 63 H 75 O 4 U: Calculated: C, 66.71, H, 6.66; Found: C, 67.15; H, IR: ν [cm -1 ] = 2900 (vs), 2846 (s), 1444 (s), 1230 (s), 1182 (w), 1159 (m), 839 (s), 802 (s), 677 (m), 522 (m), 416 (m). Synthesis of [K(2.2.2-cryptand)][(( Ad,Me ArO) 3 mes)u(o)] (2 K) A precooled solution of 2 (25.0 mg, mol) and cryptand (8.7 mg, mol) in THF (10 ml, 35 C) was pipetted into a well stirred, precooled vial charged with KC 8 (3.12 mg, mol). The reaction was stirred for 1.5 h to reach room temperature. The orange solution was filtered over a glass filter pad, the solvent was removed in vacuo, and the obtained orange solid was stirred in pentane (5 ml) for 1 h. The orange brown powder was filtered off over a por. 4 frit, washed with pentane (3 x 1 ml) and dried in vacuo to yield the title compound. Single crystals suitable for XRD analysis were obtained from diffusion of pentane in a THF / DME (50:50) solution at 35 C. Yield: 62% (20.0 mg, mol) 1 H NMR (400 MHz, benzene-d 6, RT) δh = (br. s., 18H), 9.90 (s., 3 H), 6.41 (s., 9 H), 2.58 (br. s., 9 H), 2.68 (br.s., 12 H, 2.2.2crypt), 3.52 (br.s., 4 H, 2.2.2crypt), 6.36 (br. s., 9 H), (s, 9 H), (s, 9 H), (s, 6 H), (br. s., 3 H) ppm. Elemental Analysis for C 81 H 111 KN 2 O 10 U: Calculated: C, 62.77, H, 7.22, N, 1.81; Found: C, 61.83, H, 7.39, N, Samples of 2 K were repeatedly low on carbon. IR: ν [cm 1 ] = 2968 (s), 2893 (vs), 2844 (vs), 1475 (m), 1445 (s), 1354 (vs), 1283 (vs), 1257 (vs), 1184 (w), 1162 (w), 1135 (s), 1104 (vs), 1080 (s), 1026 (m), 980 (w), 949 (s), 933 (m), 914 (w), 858 (m), 832 (s), 805 (s), 768 (vs), 577 (w), 508 (s), 468 (w), 409 (w). 3

4 Synthesis of [(( Ad,Me ArO) 3 tacn)u(o)] (4) A solution of [(( Ad,Me ArO) 3 tacn)u] (25 mg, mol) in THF (5 ml) was treated with H 2 O (0.1M in THF, 233 µl, mol) and stirred for 3 days until the reaction mixture turned blue-green. Then, the solvent was removed in vacuo. After re-dissolving in toluene (2 ml), cryptand (9.0 mg, mol) and potassium bis(trimethylsilyl)amide (4.8 mg, mol) were added to the mixture as solutions in toluene (1 ml). After complete addition, the solvent was removed immediately to yield a yellow powder that was redissolved in THF (2 ml) and treated with a solution of ferrocenium BArF 20 (18.8 mg, mol) in THF (1 ml) and stirred for 5 min. The solvent was removed in vacuo and the orange solid triturated with pentane (3 x 1 ml). The solid was suspended in pentane, collected on a frit and washed with pentane (3 x 2 ml). The product was then washed through the frit with benzene (into a new vial) and dried in vacuo to yield the title compound as an orange powder. Single crystals suitable for XRD analysis were obtained from diffusion of Si(CH 3 ) 4 in a DME solution at 35 C. Yield: 83% (21.0 mg, mol) 1 H NMR (400 MHz, benzene-d 6, RT) δh = (br. s., 3H), 5.49 (d., J = 7.4 Hz, 9 H), 0.50 (br. s., 9 H), 1.86 (br. s., 3 H), 1.91 (br. s., 9 H), 1.97 (s., 9 H), 1.99 (s., 9 H), 2.49 (br. s., 9 H), 2.52 (br. s., 3 H), 3.01 (s., 3 H), 3.90 (s., 3 H), (br. s., 3 H), (br. s., 3 H), (br. s., 3 H) ppm. Elemental Analysis for C 60 H 78 N 3 O 4 U Si(CH 3 ) 4 : Calculated: C, 62.42; H, 7.37; N, 3.41; Found: C, 62.75; H, 7.81; N, IR: ν [cm 1 ] = 2901 (vs), 2847 (s), 1512 (m), 1462 (vs), 1358 (m), 1257 (vs), 1155 (m), 1134 (m), 1105 (vs), 1032 (m), 980 (m), 951 (m), 862 (w), 827 (m), 810 (m), 777 (m), 756 (w), 638 (m), 573 (w), 519 (m), 443 (w), 419 (s). Comproportionation of [(( Ad,Me ArO) 3 tacn)u(o)] (4) with [(( Ad,Me ArO) 3 tacn)u] (3) and 1 eq. H 2 O A solution of [(( Ad,Me ArO) 3 tacn)u(o)] (8 mg, mol) in THF (2 ml) was added dropwise to a solution of [(( Ad,Me ArO) 3 tacn)u] (7.8 mg, mol) with H 2 O (0.1 M in THF, 70 µl, mol) in THF (2 ml). The solvent was removed from the blue green solution to yield a blue-green solid that was spectroscopically identified to be the U(IV) hydroxo complex [(( Ad,Me ArO) 3 tacn)u(oh)]. The 1 H NMR and IR vibrational spectra are in agreement with independently synthesized, pure samples of [(( Ad,Me ArO) 3 tacn)u(oh)] (pure by elemental-analysis). Yield: 99% (15.8 mg, mol) 1 H NMR (270 MHz, benzene-d 6, RT) δh = (br. s., 3H), (br. s., 9 H), 6.55 (br.s., 3 H), 5.55 (br. s., 12 H), 5.19 (br. s., 9 H), 4.78 (br.s., 3 H), 2.11 (br.s., 9 H), 2.88 (br. s., 3 H), 3.03 (d, J = Hz, 9 H), 5.42 (d, J = 8.09 Hz, 9 H), (br. s, 3 H), (br. s., 3 H), (br. s., 3 H) ppm. IR: ν [cm 1 ] = 3692 (w) U OH stretch, 2901 (vs), 2846 (vs), 1640 (w), 1603 (m), 1511 (m), 1463 (vs), 1438 (vs), 1418 (m), 1342 (m), 1306 (s), 1281 (s), 1257 (vs), 1224 (s), 1184 (w), 1162 (m), 1105 (s), 1086 (m), 1064 (w), 1008 (m), 996 (m), 978 (s), 951 (w), 889 (m), 860 (s), 830 (vs), 811 (s), 778 (s), 753 (m), 730 (w), 682 (w), 660 (w), 603 (w), 574 (m), 546 (m), 521 (vs), 452 (w), 414 (m). 4

5 Spectroscopic Details 1 H NMR Spectroscopy Figure 1 1 H NMR spectrum of [(( Ad,Me ArO) 3 mes)u(o)(thf)] (2), recorded in benzene-d 6. Figure 2 1 H NMR spectrum of [K(2.2.2-cryptand)][(( Ad,Me ArO) 3 mes)u(o)] (2 K), recorded in THF-d 8. 5

6 Figure 3 1 H NMR spectrum of [(( Ad,Me ArO) 3 tacn)u(o)] (4), recorded in benzene-d 6 (top: full spectrum, bottom: zoom), residual cryptand and silicon grease are marked with an asterisk. 6

7 Figure 4 1 H NMR spectrum of [(( Ad,Me ArO) 3 tacn)u(oh)], formed in the comproportionation reaction of 4 with 3 and 1 eq. H 2 O, recorded in benzene-d 6 (top: full spectrum, bottom: zoom), residual THF is marked with an asterisk. 7

8 IR Spectroscopy Figure 5 IR vibrational spectrum [(( Ad,Me ArO) 3 mes)u(o)(thf)] (2) in KBr. Figure 6 IR vibrational spectrum of [K(2.2.2-cryptand)][(( Ad,Me ArO) 3 mes)u(o)] (2 K) in KBr. 8

9 Figure 7 IR vibrational spectrum of [(( Ad,Me ArO) 3 tacn)u(o)] (4) in KBr. Figure 8 IR vibrational spectrum of [(( Ad,Me ArO) 3 tacn)u(oh)], formed in the comproportionation reaction of 4 with 3 and 1 eq. H 2 O in KBr, showing the characteristic ν (OH) stretch at 3692 cm 1. 9

10 Vis-NIR Spectroscopy Figure 9 Vis-NIR electronic absorption spectrum of [(( Ad,Me ArO) 3 tacn)u(o)] (4); 3 mm in benzene. Table 1 Vis/NIR Transitions of the complexes 2, 2 K, in THF and 4 in benzene. Band # 2 2 K 4 λ (nm) / ε (M 1 cm 1 ) λ (nm) / ε (M 1 cm 1 ) λ (nm) / ε (M 1 cm 1 ) / / / / / / / / / / / / / / / / / / / / / / / / / / / / 6 10

11 SQUID Magnetometry Figure 10 Non-linear correlation in the χ T vs. T plot of [(( Ad,Me ArO) 3 mes)u(o)(thf)] (2). Figure 11 Linear correlation in the χ T vs. T plot of [K(2.2.2-cryptand)][(( Ad,Me ArO) 3 mes)u(o)] (2 K), indicative of temperature-independent paramagnetism (TIP). 11

12 Electrochemical Studies Figure 12 Scan rate dependent CV of [(( Ad,Me ArO) 3 mes)u(=o)(thf)] (2) with a reversible U(V)/U(IV) reduction wave at E ½ = 1.42 V vs. Fc + /Fc; recorded in THF with 0.1 M TBAPF 6. Figure 13 Scan rate dependent CV of [K(2.2.2-cryptand)] [(( Ad,Me ArO) 3 mes)u(=o)(thf)] (2 K) with a reversible U(V)/U(IV) oxidation wave at E ½ = 1.42 V vs. Fc + /Fc; recorded in THF with 0.1 M TBAPF 6. 12

13 Figure 14 Scan rate dependent CV of [(( Ad,Me ArO) 3 tacn)u] (3) with a reversible U(IV)/U(III) oxidation wave at E ½ = V vs. Fc + /Fc; recorded in THF with 0.1 M TBAPF 6. Figure 15 Scan rate dependent CV of [(( Ad,Me ArO) 3 tacn)u] (3) with a quasi-reversible U(V)/U(IV) oxidation wave at E ½ = V vs. Fc + /Fc; recorded in THF with 0.1 M TBAPF 6. 13

14 Figure 16 Scan rate dependent CV of [(( Ad,Me ArO) 3 tacn)u(=o)] (4) with a reversible U(V)/U(IV) reduction wave at E ½ = V vs. Fc + /Fc; recorded in THF with 0.1 M TBAPF 6. 14

15 X-Ray Crystal Structure Determinations CCDC (for 2 K), CCDC (for 2), CCDC (for 3), and CCDC (for 4) contain the supplementary crystallographic data for this paper. This data can be obtained free of charge via (or from Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: ; deposit@ccdc.cam.ac.uk). X-Ray Crystal Structure Determination Details Suitable single crystals of the investigated compounds were embedded in protective perfluoropolyalkyether oil and transferred to the cold nitrogen gas stream of the diffractometer. Intensity data for 2 K and 4 were collected using MoK α radiation (λ = Å) on a Bruker Kappa APEX 2 IμS Duo diffractometer equipped with QUAZAR focusing Montel optics. Intensity data for 2 were collected on a Bruker Smart APEX 2 diffractometer using MoK α radiation (λ = Å, Triumph curved graphite monochromator). Data were corrected for Lorentz and polarization effects, semi-empirical absorption corrections were performed on the basis of multiple scans using SADABS 6. The structures were solved by direct methods and refined by full-matrix least-squares procedures on F 2 using SHELXTL 2014/6 7. Olex2 was used to prepare material for publication 8. All non-hydrogen atoms were refined with anisotropic displacement parameters. All hydrogen atoms were placed in positions of optimized geometry, their isotropic displacement parameters were tied to those of the corresponding carrier atoms by a factor of either 1.2 or 1.5. Crystallographic data, data collection, and structure refinement details are given in Supplementary Table 2. Molecular structures of the complexes (excluding hydrogen atoms, disorder and solvent molecules) are depicted in Supplementary Figures In 2 K both the complex anion as well as the [K(2,2,2-crypt)] cation were situated on crystallographic threefold rotation axes. The solvent molecule was also situated on a crystallographic threefold rotation axis and was disordered. Fixed distance (DFIX) and pseudo-isotropic (ISOR) restraints were applied in the refinement of the disordered atoms. The phenolate oxygen atoms were disordered. Two alternative positions were refined and resulted in site occupancies of 72(5) and 28(5) % for O1 and O1A, respectively. Compound 2 crystallized with a total of three molecules of THF (tetrahydrofuran) per formula unit. All three THF molecules were disordered. Two alternative orientations were refined in all three cases. The refined site occupancies were 43(2) and 57(2) % for the affected atoms O100 C104 and O110 C114; 57.3(9) and 42.7(9) % for C204 and C214; and 72.5(6) and 27.5(6) % for the atoms O300 C304 and O310 C314, respectively. Similarity restraints (SIMU, SAME) were applied to the displacement ellipsoids of all solvent molecule atoms. Compound 3 crystallized with one molecule of toluene per formula unit. All hydrogen atoms were placed in positions of optimized geometry, their isotropic displacement parameters were tied to those of their corresponding carrier atoms by a factor of 1.2 or 1.5. All non-hydrogen atoms were refined anisotropically. Compound 4 crystallized with one molecule of tetramethylsilane and 1.5 molecules of dimethoxyethane (DME) per formula unit. Both of the independent DME molecules suffered from disorder. In the case of the first DME molecule two alternative orientations for one of the terminal methyl groups were refined and resulted in site occupancies of 87(2) and 13(2) % for the atoms C101 and C111, respectively. The second (half) DME (C201 C206) was situated on a crystallographic inversion centre and was disordered. Similarity and pseudo-isotropic restraints were applied to the displacement ellipsoids of the atoms of the DME molecules. 15

16 Individual comments towards A- and B- level alerts of the PLATON CheckCIF routine of all complexes: Complex 2 K: No level A or -B alerts. Complex 2: Alert level A: Short Inter H...H Contact H66A.. H31G Ang. Author Response: This apparent short contact involves H31G which is a hydrogen atom of the minor fraction (less than 28 %) of a disordered tetrahydrofuran solvent molecule. Complex 3: No level A or -B alerts. Complex 4: Alert level A: Short Inter XH3.. XHn H4B.. H11B Ang. Author Response: H11B is a hydrogen atom belonging to the minor component of a \ disordered methyl group of a dimethoxyethane solvent molecule (occupancy < 0.15) that has been placed in a position of optimized geometry. H10I and H20G do also belong to \ carbon atoms of in part disordered dimethoxyethane solvent molecules. Alert level A: Short Inter D...A Contact O202.. O Ang. Author Response: Both atoms O202 and O205 belong to a dimethoxyethane solvent \ molecule that is situated on a crystallographic inversion centre and is disordered. The \ apparent short intermolecular contacts are obviously between non-realized positions of the only partly occupied disordered sites. Alert level A: Short Inter D...A Contact O202.. O Ang. Author Response: Both atoms O202 and O205 belong to a dimethoxyethane solvent \ molecule that is situated on a crystallographic inversion centre and is disordered. The \ apparent short intermolecular contacts are obviously between non-realized positions of the only partly occupied disordered sites. Alert level B: Short Inter XH3.. XHn H10I.. H20G Ang. Author Response: H11B is a hydrogen atom belonging to the minor component of a \ disordered methyl group of a dimethoxyethane solvent molecule (occupancy < 0.15) that has been placed in a position of optimized geometry. H10I and H20G do also belong to \ carbon atoms of in part disordered dimethoxyethane solvent molecules. 16

17 Spacefilling Models of 1 and 3, Together with Illustration of Their Active Sites for H2O Reduction Figure 17 Upper panel: Spacefilling model and schematic depiction of the H2O substrate attack at the kinetically favored equatorial position in the case of complex 1. Lower panel: Spacefilling model and schematic depiction of the H2O substrate attack at the well protected and less favored top axial position in the case of complex 3. In the space filling models, hydrogen is depicted in light grey, carbon in dark grey, oxygen in red, and uranium in magenta. 17

18 Table 2 Crystallographic data, data collection and refinement details of 2 K, 2, 3, and 4. 2 K Empirical formula C 86 H 123 KN 2 O 10 U C 79 H 107 O 8 U C 60 H 78 N 3 O 3 U, C 7 H 8 C 70 H 105 N 3 O 7 SiU Mol. weight Crystal shape, color prism, orange prism, red block, brown block, orange Crystal size [mm] Temperature [K] 100(2) 100(2) 100(2) 100(2) Crystal system cubic monoclinic monoclinic monoclinic Space group P2 1 3 C2/c P2 1 /n P2 1 /n a [Å] (2) (2) (5) (2) b [Å] (2) (6) (7) (5) c [Å] (2) (2) (7) (4) α [ ] β [ ] (3) (3) (3) γ [ ] V [Å 3 ] 7849(2) 13368(2) (3) 6573(2) Z ρ [g cm 3 ] (calc.) µ [mm 1 ] F (000) T min ; T max 0.687; ; ; ; Θ interval [ ] Θ Θ Θ Θ 57.5 Coll. refl Indep. refl.; R int 6221; ; ; ; Obs. refl. F 0 4σ(F) No. ref. param wr 2 (all data) R 1 (F 0 4σ(F)) GooF on F ρ max/min 0.972; ; ; ;

19 Table 3 Selected structural parameters of complexes 2, 2 K, 3, and 4 with bond distances in Å and angles in. 2 2 K 3 4 U O oxo 1.830(2) 1.891(3) 1.839(2) U O Ar U C Ar C Ar C Ar 2.163(2) 2.173(2) 2.182(2) 3.041(2) 3.189(2) 3.072(2) 3.003(3) 3.017(3) 3.005(2) 1.407(4) 1.412(5) 1.413(4) 1.406(4) 1.414(5) 1.408(4) 2.24(1) 2.24(1) 2.24(1) 3.139(7) 3.132(6) 3.139(7) 3.132(6) 3.139(7) 3.132(6) 1.40(1) 1.38(1) 1.38(1) 1.40(1) 1.38(1) 1.40(1) 2.213(1) 2.230(1) 2.240(1) 2.199(2) 2.172(2) 2.186(2) U mes centr (2) 2.810(1) U tacn centr (2) 2.840(2) U OOP 0.060(2) 0.063(1) 0.880(1) 0.145(2) U N tacn 2.653(2) 2.666(2) 2.668(2) 2.698(2) 2.718(2) mes centr. U O oxo (2) tacn centr. U O oxo

20 Graphical Representations Figure 18 Molecular structure of 2 K with the applied numbering scheme (50 % probability ellipsoids, hydrogen atoms and solvent molecules omitted for clarity). Figure 19 Molecular structure of 2 with the applied numbering scheme (50 % probability ellipsoids, hydrogen atoms and solvent molecules omitted for clarity). 20

21 Figure 20 Molecular structure of 3 with the applied numbering scheme (50 % probability ellipsoids, hydrogen atoms and toluene solvent molecules omitted for clarity). Figure 21 Molecular structure of 4 with the applied numbering scheme (50 % probability ellipsoids, hydrogen atoms and DME solvent molecules omitted for clarity). 21

22 Theoretical Calculations All the structures reported in this study were fully optimized with the Becke s 3-parameter hybrid functional combined with the non-local correlation functional provided by Perdew/Wang (denoted as B3PW91) 9,10. The relativistic energy-consistent small-core pseudopotential is used for uranium atom, taking from the Stuttgart-Cologne group s database, in combination with its adapted segmented basis set in order to study the reactivity in which a change in oxidation state is present in most of the cases For the rest of the atoms the 6-31G(d,p) basis set is used In all computations no constrains were imposed on the geometry. This is because charged species are present in the reaction and all stationary points have been identified for minimum (number of imaginary frequencies Nimag=0). GAUSSIAN09 program suite was used in all calculations 17. Optimized Structures of Crystallographically Characterized Complexes Table 4 Cartesian coordinates of the optimized structure of [(( Ad,Me ArO) 3 mes)u(=o)(thf)] (2). U O O O O O C C C C C C C H H H C H H H

23 C H H H C H H C C C C H C C H C C H C H C H C H H C H H C H H

24 C H H C H H C H H C H H H C H H C C C C H C C H C C H C H C H

25 C H H C H H C H H C H H C H H C H H C H H H C H H C C C C H C

26 C H C C H C H C H C H H C H H C H H C H H C H H C H H C H H H

27 C H H C H H C H H C H H Table 5 Cartesian coordinates of the optimized structure of the anion [(( Ad,Me ArO) 3 mes)u(=o)] of 2 K. U O O O O O C C C C C C C H H H

28 C H H H C H H H C H H C C C C H C C H C C H C H C H C H H C H

29 H C H H C H H C H H C H H C H H H C H H C C C C H C C H C C H

30 C H C H C H H C H H C H H C H H C H H C H H C H H H C H H C C

31 C C H C C H C C H C H C H C H H C H H C H H C H H C H H C H H

32 C H H H C H H C H H C H H C H H Optimized Structures for the Reaction Profile Presented in Figure 6 of the Main Text. Table 6 Cartesian coordinates of the optimized structure of [(( Ad,Me ArO) 3 mes)u(h 2 O)] (A)

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37 Table 7 Cartesian coordinates of the optimized structure of the first transitionstate (structure B) involved in the oxidative addition of water to

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42 Table 8 Cartesian coordinates of the optimized structure of the U(V)-hydroxo-hydride intermediate [(( Ad,Me ArO) 3 mes)u(oh)(h)] (C)

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