Supporting Information

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1 Supporting Information Wiley-VCH Weinheim, Germany

2 An Isolable Side-on Superoxonickel Complex [LNi(O 2 )] with Planar Tetracoordinate Ni II and Its Conversion to the Unusual LNi(μ-OH) 2 NiL Complex with Planar Tetracoordinate and Tetrahedral Ni II Sites (L = ß-Diketiminato)** Shenglai Yao, Eckhard Bill, Carsten Milsmann, Karl Wieghardt and Matthias Driess* A. Experimental Section General Considerations: All experiments and manipulations were carried out under dry oxygen-free nitrogen (except for the synthesis of compound 1) using standard Schlenk techniques or in an MBraun inert atmosphere drybox containing an atmosphere of purified nitrogen. Solvents were dried by standard methods and freshly distilled prior to use. The starting material 1 [1] (L = CH{(CMe)(2,6- i Pr 2 C 6 H 3 N} 2 ) was prepared according to literature procedure. 1 H-NMR spectra were recorded on Bruker Spectrometer AS 200. Chemical shifts of the deuterated solvents in 1 H NMR data: benzene-d 6 : δ(c 6 D 5 H) = 7.15 ppm. Single-Crystal X-ray Structure Determinations: Crystals were each mounted on a glass capillary in perfluorinated oil and measured in a cold N 2 flow. The data of Compounds 1, and 3 were collected on an Oxford Diffraction Xcalibur S Sapphire at 150 K (Mo-Kα radiation, λ = Å). The structures were solved by direct methods and refined on F 2 with the SHELX-97 [2] software package. The positions of the H atoms were calculated and considered isotropically according to a riding model. The oxygen atoms O1a and O1b in 3 are each statistically disordered over two orientations in a population ratio of 0.51:0.49. CCDC (1) and (3) contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via or by ing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax:

3 Magnetic Susceptibility Measurement: Magnetic susceptibility data were measured from powder samples of solid material in the temperature range K with a SQUID susceptometer with a field of 1.0 T (MPMS-7, Quantum Design, calibrated with standard palladium reference sample, error < 1%). The experimental data were corrected for underlying diamagnetism by use of tabulated Pascal s constants, [3, 4] as well as for temperature-independent paramagnetism (TIP). The susceptibility and magnetization data were simulated with our own package julx for exchange coupled systems. [5] The simulations are based on the usual spin-hamilton operator for mononuclear complexes with spin S=1/2 for 1 and S = 1 for 3: H ˆ = gβs v ˆ B v + D [ S ˆ 2 z 1/3 S(S +1) + E /D( S ˆ 2 x S ˆ 2 y )] eq. 1 where g is the average electronic g value, and D and E/D are the axial zero-field splitting and rhombicity parameters. Intermolecular interactions were considered by using a Weiss temperature, Θ W, as perturbation of the temperature scale, kt' = k(t-θ W ) for the calculation. Powder summations were done by using a 16-point Lebedev grid. EPR Measurement: X-band EPR derivative spectra were recorded on a Bruker ELEXSYS E500 spectrometer equipped with the Bruker standard cavity (ER4102ST) and a helium flow cryostat (Oxford Instruments ESR 910). Microwave frequencies were calibrated with a Hewlett-Packard frequency counter (HP5352B), and the field control was calibrated with a Bruker NMR field probe (ER035M). The spectra were simulated with the program GFIT (by E.B.) for the calculation of powder spectra with effective g values and anisotropic line widths (Gaussian line shapes were used). Compound 1 A solution of 2 (0.59 g, 0.56 mmol) in toluene (40 ml) was cooled to -78 C. The N 2 atmosphere in the flask was exchanged to dried oxygen. After stirring for 15 min, the reaction mixture was allowed to warm to room temperature and stirred further for 30 min in the oxygen atmosphere. In the course of stirring the colour of the solution changed from brown red to green. Volatiles were removed in vacuo, and the residue was washed with n-hexane (20 ml) and then extracted with toluene (50 ml). After concentration and cooling to -20 C for 12 h, compound 1 crystallized from the solution as green crystals (0.48 g, 0.94 mmol, 84 %). M.p. 139 C (decomp.) 1 H NMR ( MHz, C 6 D 6, 298K): δ = -3.7 (1H), 1.0 (16H), 3.2 (12H), 6.6 (4H), 7.8 (2H), 11.6 (6H). EI-MS: m/z (%): (5, [M] + ), (100, [M-O 2 ] + ). Elemental analysis (%): calcd for C 29 H 41 N 2 NiO 2 : C, 68.5; H, 8.1; N, 5.5. Found: C, 68.8; H, 7.9; N, 5.3. UV-vis (toluene): 360 nm (15000 M -1 cm -1 ), 420 nm (365 M -1 cm -1 ), 460 nm (190 M -1 cm - 1 ), 590 nm (170 M -1 cm -1 ), 980 nm (430 M -1 cm -1 ). IR (KBr, cm -1 ): ν = 444 (w), 635 (w), 718 (w), 723 (w), 761 (m), 770 (w), 800 (m), 936 (m), 971 (m, 16 O- 16 O str.), 1030 (w), 1056 (w), 1100 (w), 1180 (w), 1235 (w), 1254 (m), 1319 (s), 1372 (s), 1438 (s), 1455 (m), 1530 (s), 1556 (m), 1584 (w), 1635 (w), 2866 (m), 2924 (m), 2961 (s), 3055 (w).

4 %T ν(o 16 -O 16 ) 971 cm -1 ν(o 18 -O 18 ) 919 cm Wavenumbers (cm-1) Figure 1. IR spectrum of 1. Assignment of the O-O vibrational modes in accord with isotope labelling experiments Figure 2: X-band EPR spectrum of 1 in frozen toluene at 50 K (microwave frequency GHz, power 6.3 mw, modulation 0.3 mt/ 100kHz). The red line is a powder simulation with anisotropic g values as indicated.

5 Figure 3: Temperature dependence of the effective magnetic moment of solid 1 with applied field B = 1 T. The red line is a simulation with S = 1/2 and g av = The decrease of μ eff below 10 K is due to the combined effect of field saturation and weak intermolecular interaction according to a Weiss temperature of about Θ W = -0.1 K. The experimental data have been corrected for a TIP contribution to χ of 150x10-6 emu. Compound 3 Method A. A solution of 2 (0.47 g, 0.45 mmol) in toluene (30 ml) was cooled to -20 C. The N 2 atmosphere in the flask was exchanged to dried N 2 O. After stirring for 10 min, the reaction mixture was allowed to warm to room temperature and stirred further for 2h in the N 2 O atmosphere. In the course of stirring the colour of the solution changed from brown red to brown yellow. Volatiles were removed in vacuo, and the residue was extracted with n- hexane (50 ml). After concentration and cooling to -20 C for 12 h, compound 3 crystallized from the solution as green crystals (0.21 g, 0.21 mmol, 47 %). Method B. To a cooled (-78 C) solution of 2 ( 0.14 g, 0.26 mmol) in toluene (5 ml) was added a solution of 1 (0.14g, 0.13 mmol) in toluene (5 ml) with stirring. After the addition the reaction mixture was allowed to warm to room temperature and stirred further for 2 h. Volatiles were removed in vacuo, and the residue was extracted with n-hexane (25 ml). After concentration and cooling to -20 C for 12 h, compound 3 crystallized from the solution as green crystals (0.10 g, 0.10 mmol, 39 %). Method C. To a solution of 1 ( 0.16 g, 0.31 mmol) in toluene (10 ml) was added PPh 3 ( 0.16 g, 0.62 mmol) at room temperature. After stirring for 12 h, the 1 H and 31 P NMR spectra showed that compound 3 and Ph 3 P=O were formed along with unconsumed PPh 3 (Ph 3 P=O: PPh 3 1:1). Volatiles were removed in vacuo, and the residue was extracted with n-hexane (25 ml). After concentration and cooling to -20 C for 12 h, compound 3 crystallized from the solution as green crystals (0.05 g, 0.05 mmol, 33 %). M.p. 284 C (decomp.) 1 H NMR ( MHz, C 6 D 6, 298K): δ = -16.7(m), -7.9(m), 1.4(d), 3.9(d), 4.0(t), 6.5 (br.), 11.1(m), 35.7(br.). EI-MS: m/z (%): (8, [M] + ), (2, [M-OH] + ),476.4 (100, [1/2M-OH] + ). Elemental analysis (%): calcd for C 58 H 84 N 4 Ni 2 O 2 : C, 70.6; H, 8.6; N, 5.7. Found: C, 70.3; H, 8.5; N, 5.5. UV-vis (n-hexane): 380 nm (9200 M -1 cm -1 ), 400 nm (8800 M -1 cm -1 ). IR (KBr, cm -1 ): ν = 458 (w), 519 (w), 741 (w), 762 (m), 797 (m), 867 (w), 935 (w), 1026 (w), 1057 (w), 1100 (w), 1179 (m), 1254 (m), 1318 (m), 1362 (m), 1404 (s), 1436 (s), 1461 (s), 1531 (s), 1654 (w), 2868 (m), 2928 (m), 2962 (s), 3059 (w), 3620 (w), 3653 (w).

6 Figure 4: Temperature dependence of the effective magnetic moment of solid 3 with applied field B = 1 T. The red line is a simulation with S = 1 and the parameters given in the inset. B. Quantum-chemical Calculations All DFT calculations were performed with the ORCA program package. [6] The geometry optimizations of the complexes were carried out at either the B3LYP [7-9] or the BP86 [7, 10, 11] level of DFT. Single-point calculations on the optimized geometries were carried out using the B3LYP functional. This hybrid functional often gives better results for transition metal compounds than pure gradient-corrected functionals, especially with regard to metalligand covalency. [12] The all-electron Gaussian basis sets were those developed by the Ahlrichs group. [13, 14] Triple-ζ quality basis sets TZV(P) with one set of polarization functions on the metals and on the atoms directly coordinated to the metal center were used. [14] For the carbon and hydrogen atoms, slightly smaller polarized split-valence SV(P) basis sets were used, that were of double-ζ quality in the valence region and contained a polarizing set of d- functions on the non-hydrogen atoms. [13] Auxiliary basis sets used to expand the electron density in the resolution-of-the-identity (RI) approach were chosen, [15-17] where applicable, to match the orbital basis. The SCF calculations were tightly converged ( E h in energy, E h in the density change and in maximum element of the DIIS error vector). The geometry optimizations for all complexes were carried out in redundant internal coordinates without imposing symmetry constraints. In all cases the geometries were considered converged after the energy change was less than E h, the gradient norm and maximum gradient element were smaller than E h Bohr -1 and E h Bohr -1, respectively, and the root-mean square and maximum displacements of all atoms were smaller than Bohr and Bohr, respectively. Because several broken symmetry solutions to the spin-unrestricted Kohn-Sham equations may be obtained, the general notation BS(m,n) [18] has been adopted, where m (n) denotes the number of spin-up (spin-down) electrons at the two interacting fragments. Canonical and quasi-restricted orbitals, as well as spin density plots were generated with the program Molekel. [19]

7 z y x d xy O 2 π out of plane 0.50 S total = ½ S Ni = 0 d yz d z 2 d xz d x 2 -y 2 Figure 5. Calculated spin density and frontier orbitals of 1. Figure 6. Calculated structure of 1.

8 Overlap S = 0.81 Magnetic Orbitals S total = ½ S Ni = 1 Figure 7. Calculation of 1 with tetrahedral Ni. Compund 1 is 19.1 kcal mol -1 disfavoured in comparison to 1.

9 Figure 8. Calculations of the proposed transient species LNi-O 4 with S = 1/2 vs. S = 3/2 spin state and their spin density.

10 Figure 9. Calculation of the spin density of LNi(µ-OH) 2 NiL 3. Figure 10. Calculated structure of 3.

11 Table 1. Cartesian coordinates (Å) of 1 obtained from a geometry optimization at the B3LYP level of DFT. x y z Ni O O N C C C N C C C C C C C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H

12 H H H H H H H H H H H H H H H H H H H H H H H H H H Table 2. Cartesian coordinates (Å) of 1 obtained from a geometry optimization at the B3LYP level of DFT. x y z Ni N C C C N O O C C C C C C C C C C

13 C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H

14 H Table 3. Cartesian coordinates (Å) of 3 obtained from a geometry optimization at the BP86 level of DFT. x y z Ni N N O O C C C C C C C C C C C C C C C C C C C C C C C C C C C C C Ni N N C C C C C C C

15 C C C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H

16 H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H

17 Table 4. Cartesian coordinates (Å) of 4 obtained from a geometry optimization at the B3LYP level of DFT assuming a spin state of S = 1/2. x y z Ni O N N C C C E-04 C E-04 C C C C C C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H

18 H H H H H H H H H H H H H H H H H H H H H H H H H Table 5. Cartesian coordinates (Å) of 4 obtained from a geometry optimization at the B3LYP level of DFT assuming a spin state of S = 3/2. x y z Ni O E-04 N N C E-04 C C E-03 C E-04 C C C C C C C C C C C C C

19 C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H

20 References for Supporting Information: [1] G. Bai, P. Wei, D. W. Stephan, Organometallics, 2005, 24, [2] G. M. Sheldrick, SHELX-97 Program for Crystal Structure Determination, Universität Göttingen (Germany) [3] C. J. O'Connor, Prog. Inorg. Chem. 1982, 29, 203. [4] Weast, R. C.; Astle, M. J., CRC Handbook of Chemistry and Physics. CRC Press Inc.: Boca Raton, Florida, [5] available from E.B.: [6] F. Neese, Orca an ab initio, DFT and Semiempirical Electronic Structure Package, Version 2.6, Revision 4; Institut für Physikalische und Theoretische Chemie, Universität Bonn, Bonn (Germany), May [7] A. D. Becke, J. Chem. Phys. 1986, 84, [8] A. D. Becke, J. Chem. Phys. 1993, 98, [9] C. T. Lee, W. T. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785. [10] J. P. Perdew, W. Yue, Phys. Rev. B 1986, 33, [11] J. P. Perdew, Phys. Rev. B 1986, 33, [12] F. Neese, E. I. Solomon, In Magnetoscience: From Molecules to Materials; Miller, J. S., Drillon, M., Eds.; Wiley: New York, 2002; Vol. 4, p 345. [13] A. Schäfer, H. Horn, R. Ahlrichs, J. Chem. Phys. 1992, 97, [14] A. Schäfer, C. Huber, R. Ahlrichs, J. Chem. Phys. 1994, 100, [15] K. Eichkorn, F. Weigend, O. Treutler, R. Ahlrichs, Theor. Chem. Acc. 1997, 97, 119. [16] K. Eichkorn, O. Treutler, H. Öhm, M. Häser, R. Ahlrichs, Chem. Phys. Lett. 1995, 240, 283. [17] K. Eichkorn, O. Treutler, H. Öhm, M. Häser, R. Ahlrichs, Chem. Phys. Lett. 1995, 242, 652. [18] B. Kirchner, F. Wennmohs, S. Ye, F. Neese, Curr. Opin. Chem. Biol. 2007, 11, 134. [19] Molekel, Advanced Interactive 3D-Graphics for Molecular Sciences, available under