Distorted Tetrahedral Nickel-Nitrosyl Complexes: Spectroscopic Characterization and Electronic Structure

Submitted to Journal of Biological Inorganic Chemistry as a Full article Distorted Tetrahedral Nickel-Nitrosyl Complexes: Spectroscopic Characterization and Electronic Structure Shoko Soma, Casey Van Stappen, Mercedesz Kiss, Robert K. Szilagyi, Nicolai Lehnert, Kiyoshi Fujisawa Electronic supplementary material The online version of this article (doi:xxxx/xxx) contains supplementary material, which is available to authorized users. S. Soma, K. Fujisawa ( ) Department of Chemistry, Ibaraki University, Mito, 310-8512, Ibaraki, Japan e-mail: kiyoshi.fujisawa.sci@vc.ibaraki.ac.jp M. Kiss, R. K. Szilagyi ( ) Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States and MTA-ELTE Chemical Structure & Function Momentum Laboratory, Budapest, Hungary e-mail: szilagyi@montana.edu C. Van Stappen, N. Lehnert ( ) Department of Chemistry and Department of Biophysics, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan, 48109, United States e-mail: lehnertn@umich.edu C. Van Stappen (current address) Max-Planck Institute for Chemical Energy Conversion Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany e-mail: casey.van-stappen@cec.mpg.de SUP - 1

Experimental details This complex has been reported before, but was prepared and crystallized here by a modified method. [NiCl2(PPh3)2] (9 g, 1.67 mmol), PPh3 (41 g, 1.68 mmol), and NaNO2 (1.89 g, 27.4 mmol) were dissolved in tetrahydrofuran (30 ml). The resulting brown suspension was stirred and refluxed under an argon atmosphere for 1 h. The suspension was allowed to cool to room temperature and filtrated through Celite, followed by drying of the solution in vacuo. Recrystallization from dichloromethane / heptane at room temperature gave dark purple crystals. Yield: 0.541 g, 34 mmol (50%). Anal. Calcd for C36H30ClNNiOP2: C, 66.65; H, 4.66; N, 2.16. Found: C, 66.43; H, 4.59; N, 2.17. IR (KBr, cm 1 ): 3053 m, 1966 w, 1889 w, 1817 w, 1715 vs, 1482 s, 1434 s, 1308 w, 1183 w, 1156 w, 1095 s, 1027 m, 997 m, 747 s, 693 s, 521 s. Far IR (CSI, cm 1 ): 618 w, 573 m, 521 vs, 508 vs, 494 s, 448 m, 424 m, 380 w, 280 m, 253 w. UV vis (CH2Cl2, λ, nm) (ε, M 1 cm 1 ): 265 (21000), 382 (310), 504 (580), 631 (710). DR(solid, λ, nm): 382, 512, 624. 1 H-NMR (CDCl3, δ, ppm, 500 MHz): 7.23 (dd, J = 7.5 Hz, 12H, o PhH), 7.34 (m, J = 7.0 Hz, 18H, m,p PhH). 13 C-NMR (CDCl3, δ, ppm, 125 MHz): 128.6 (3,5 PhC), 130.1 (4 PhC), 132.7 (1 PhC), 134.3 (2,6 PhC). 31 P-NMR (CDCl3, δ, ppm, 200 MHz): 37.4 (s). [Ni(NO)(Br)(PPh 3 ) 2 ] This complex has been reported before, but was prepared and crystallized here by a modified method. [NiBr2(PPh3)2] (2.01 g, 2.70 mmol), PPh3 (0.733 g, 2.79 mmol), and NaNO2 (3.23 g, 46.8 mmol) were dissolved in tetrahydrofuran (40 ml). The resulting brown suspension was stirred and refluxed under an argon atmosphere for 1 h. The suspension was allowed to cool to room temperature and filtrated through Celite, followed by drying of the solution in vacuo. Recrystallization from dichloromethane / heptane at room temperature gave dark purple crystals. Yield: 1.39 g, 2.01 mmol (74%). Anal. Calcd for C36H30BrNNiOP2: C, 62.39; H, 4.36; N, 2.02. Found: C, 62.44; H, 4.38; N, 2.05. IR (KBr, cm 1 ): 3438 w, 3049 m, 1966 w, 1895 w, 1822 w, 1731 vs, 1479 s, 1432 s, 1310 m, 1180 m, 1159 m, 1095 s, 1027 m, 997 m, 742 s, 695 s, 506 s. Far IR (CSI, cm 1 ): 618 w, 571 m, 521 vs, 508 vs, 494 s, 447 m, 435 m, 424 m, 398 w, 374 w, 252 w, 208 m, 195 w, 163 w. UV vis (CH2Cl2, λ, nm) (ε, M 1 cm 1 ): 265 (17000), 385 (390), 517 (600), 620 (680). DR(solid, λ, nm): 388, 514, 624. 1 H-NMR (CDCl3, δ, ppm, 500 MHz): 7.24 (dd, J = 8.0 Hz, 12H, o PhH), 7.34 (m, J = 6.3 Hz, 18H, m,p PhH). 13 C-NMR (CDCl3, δ, ppm, 125 MHz): 128.6 (3,5 PhC), 13 (4 PhC), 132.3 (1 PhC), 134.2 (2,6 PhC). 31 P-NMR (CDCl3, δ, ppm, 200 MHz): 35.0 (s). [Ni( 15 NO)Br(PPh 3 ) 2 ] The 15 N-labeled complex was prepared by the same method as the corresponding unlabeled complex using Na 15 NO2. IR (KBr, cm 1 ): 3049 m, 1965 w, 1894 w, 1826 w, 1698 vs, 1480 s, 1433 s, 1309 w, 1180 w, 1159 w, 1095 s, 1027 m, 997 m, 743 s, 695 s, 521 s. Far IR (CSI, cm 1 ): 618 w, 562 m, 521 vs, 507 vs, 495 s, 446 m, 435 m, 424 m, 398 w, 367 w, 252 w, 208 m, 194 w, 163 w. SUP - 2

Fig. S1 Molecular structures of (left) and [Ni(NO)(Br)(PPh 3 ) 2 ] (right) showing 50% thermal ellipsoids and the atom-labeling scheme. Hydrogen atoms are omitted for clarity. Relevant bond lengths (Å) and angles ( ): : Ni1 N1, 1.6808(14); Ni1 Cl1, 2.2778(6); Ni1 P1, 2.2836(6); Ni1 P2, 2.2470(6); N1 O1, 1.160(2); N1 Ni1 Cl1, 127.76(6); N1 Ni1 P1, 110.96(5); N1 Ni1 P2, 105(5); Cl1 Ni1 P1, 99.467(19); Cl1 N41 P2, 98.399(17), P1 Ni1 P2, 127(2); Ni1 N1 O1, 152.17(15). [Ni(NO)(Br)(PPh 3 ) 2 ]: Ni1 N1, 1.672(3); Ni1 Br1, 2.4064(7); Ni1 P1, 2.2627(11); Ni1 P2, 2.2500(10); N1 O1, 1.167(4); Ni2 N2, 1.684(3); Ni2 Br2, 2.4057(7); Ni2 P3, 2.2659(11); Ni2 P4, 2.2518(10); N2 O2, 1.161(4); N1 Ni1 Br1, 126.24(10); N1 Ni1 P1, 104.00(11); N1 Ni1 P2, 103.56(10); Br1 Ni1 P1, 104.69(3); Br1 Ni1 P2, 98.67(3), P1 Ni1 P2, 121.51(4); Ni1 N1 O1, 152.5(3); N2 Ni2 Br2, 126.45(10); N2 Ni2 P3, 105.25(12); N2 Ni2 P4, 102.60(10); Br2 Ni2 P3, 103.53(3); Br2 Ni2 P4, 99.14(3), P3 Ni2 P4, 121.71(4); Ni2 N2 O2, 15(3). In [Ni(NO)(Br)(PPh 3 ) 2 ], two crystallographically independent molecules are found in the unit cell whose structural features are essentially identical. Molecule 1 is presented here. SUP - 3

oscillator strength x 1000 0.9 0.7 0.5 [Ni(Cl)(L3)] 1.4 1.2 0.3 0.1 8325 8330 8335 8340 8345 8350 8355 8360 excitation/photon energy, ev XAS intensity oscillator strength x 1000 0.9 0.7 0.5 0.3 [Ni(NO)(L3)] 1.2 0.1 8325 8330 8335 8340 8345 8350 8355 8360 excitation/photon energy, ev XAS Intensity oscillator strength x 1000 0.5 0.3 0.1 1.4 1.2 XAS Intensity oscillator strength x 1000 0.5 [Ni(NO)(Br)(PPh 3 ) 2 ] 0.3 0.1 1.4 1.2 XAS Intensity 8325 8330 8335 8340 8345 8350 8355 8360 excitation/photon energy, ev 8325 8330 8335 8340 8345 8350 8355 8360 excitation/photon energy, ev oscillator strength x 1000 0.5 0.3 0.1 1.2 XAS Intensity oscillator strength x 1000 0.5 0.3 0.1 [Ni(Br) 2 (PPh 3 ) 2 ] 1.6 1.4 1.2 XAS Intensity 8325 8330 8335 8340 8345 8350 8355 8360 excitation/photon energy, ev 8325 8330 8335 8340 8345 8350 8355 8360 excitation/photon energy, ev oscillator strength x 1000 0.5 0.3 0.1 [Ni(I) 2 (PPh 3 ) 2 ] 1.4 1.2 XAS Intensity 8325 8330 8335 8340 8345 8350 8355 8360 excitation/photon energy, ev Fig. S2 Simulated Ni K-edge spectra with lines representing each excited state with significant oscillator strength. The envelope spectrum was generated by pseudo-voigt line shape broadening with 2.2 ev line widths. Dashed line represents the experimental spectrum. SUP - 4

oscillator strength x 1000 3.0 2.5 2.0 1.5 0.5 [Ni(Cl)(L3)] 1.4 1.2 XAS intensity oscillator strength x 1000 0.9 0.7 0.5 0.3 0.1 1.2 XAS Intensity 2817 2819 2821 2823 2825 2827 2829 excitation/photon energy, ev 2817 2819 2821 2823 2825 2827 2829 excitation/photon energy, ev 3.0 1.6 2.5 1.4 oscillator strength x 1000 2.0 1.5 1.2 XAS intensity 0.5 2817 2819 2821 2823 2825 2827 2829 excitation/photon energy, ev Fig. S3 Simulated Cl K-edge spectra with lines representing each excited state with significant oscillator strength. The envelope spectrum was generated by pseudo-voigt line shape broadening with 1.2 ev line widths. Dashed line represents the experimental spectrum. SUP - 5

oscillator strength x 1000 7.0 6.0 5.0 4.0 3.0 2.0 1.8 1.6 1.4 2.0 2140 2142 2144 2146 2148 2150 excitation/photon energy, ev 1.2 XAS intensity oscillator strength x 1000 6.0 [Ni(NO)(Br)(PPh 3 ) 2 ] 5.0 4.0 3.0 2.0 2.0 1.8 1.6 1.4 2140 2142 2144 2146 2148 2150 TD DFT excitation energy, ev 1.2 XAS intensity oscillator strength x 1000 7.0 2.0 1.8 6.0 1.6 5.0 1.4 4.0 1.2 3.0 2.0 2140 2142 2144 2146 2148 2150 excitation/photon energy, ev XAS Intensity oscillator strength x 1000 5.0 4.5 4.0 3.5 3.0 2.5 2.0 [Ni(Br) 2 (PPh 3 ) 2 ] 2.0 1.8 1.6 1.4 1.5 0.5 2140 2142 2144 2146 2148 2150 excitation/photon energy, ev 1.2 XAS Intensity oscillator strength x 1000 7.0 6.0 5.0 4.0 3.0 [Ni(I) 2 (PPh 3 ) 2 ] 2.0 2140 2142 2144 2146 2148 2150 excitation/photon energy, ev Fig. S4 Simulated P K-edge spectra with lines representing each excited state with significant oscillator strength. The envelope spectrum was generated by pseudo-voigt line shape broadening with 1.6 ev line widths. Dashed line represents the experimental spectrum. 2.0 1.8 1.6 1.4 1.2 XAS Intensity SUP - 6

[Ni(NO)(Cl)(PPh3)2] [Ni( 14 NO)(Br)(PPh3)2] Transmittance [Ni( 15 NO)(Br)(PPh3)2] [Ni(Cl)(L3)] [Ni(NO)(L3)] 4000 3000 2000 1000 Wavenumber / cm / cm 1-1 Fig. S5 IR spectra of all of the complexes. [Ni( 14 NO)(Br)(PPh3)2] Transmittance [Ni( 15 NO)(Br)(PPh3)2] [Ni( 14 NO)(L3)] [Ni( 15 NO)(L3)] 650 550 450 350 250 150 Wavenumber / cm/ cm -1 1 Fig. S6 Far-IR spectra of the NO complexes. SUP - 7

[Ni(NO)(Cl)(PPh3)2] Transmittance [Ni(NO)(Br)(PPh3)2] 600 500 400 300 200 Wavenumber / cm 1-1 Fig. S7 Far-IR spectra of the NO complexes. SUP - 8

2.5 X 10 4 2.0 X 10 4 [Ni(NO)(Cl)(PPh 3 ) 2 ] [Ni(NO)(Br)(PPh 3 ) 2 ] [Ni(Cl)(L3)] [Ni(NO)(L3)] Epsilon / M -1 cm -1 1.5 X 10 4 X 10 4 5000 0 300 400 500 600 700 800 900 1000 Wavelength / nm Fig. S8 UV-Vis spectra of all complexes in dichloromethane solution (240-1040 nm region). Absorbance 400 600 Wavelengh / nm 800 1000 Fig. 9 UV-Vis spectral comparison of [Ni(Cl)(L3)] (red line) and [Ni(Br)(L3)] (blue line) (unpublished results). SUP - 9

[Ni(NO)Cl(PPh 3 ) 2 ] [Ni(NO)Br(PPh 3 ) 2 ] [Ni(NO)(L3)] [NiCl(L3)] Relative reflectivity (arbitrary unit) 400 600 800 1000 1200 1400 1600 Wavelength / nm Fig. S10 Diffuse reflectance spectra of all complexes (solid, 300-1600 nm). SUP - 10

o-phh m,p-phh TMS o-phh m,p-phh [Ni(NO)(Br)(PPh 3 ) 2 ] TMS Grease C(CH 3 ) 3 [Ni(NO)(L3)] 4-pzH CH(CH 3 ) 2 CH(CH 3 ) 2 TMS Fig. S11 1 H-NMR spectra of the NO complexes in CDCl3 solution at room temperature. 4-pzH CH(CH 3 ) 2 BH CH(CH 3 ) 2 C(CH 3 ) 3 Fig. S12 1 H-NMR spectra of [Ni(Cl)(L3)] in CDCl3 solution at room temperature. SUP - 11

First Derivative of XAS intensity 35 30 25 20 15 10 05 00 8325 8335 8345 8355-05 -10 A Ni K-edge [Ni(Cl)(L3)] [Ni(NO)(L3)] [Ni(NO)(Br)(PPh 3 ) 2 ] [Ni(Br) 2 (PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] [NiF 2 ] Ni foil Second Derivative of XAS intensity -15 Photon Energy, ev 02 01 00 8325 8335 8345 8355-01 -02 B [Ni(Cl)(L3)] [Ni(NO)(L3)] [Ni(NO)(Br)(PPh 3 ) 2 ] [Ni(Br) 2 (PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] [NiF 2 ] Ni foil -03 Photon Energy, ev Fig. S13 First (A) and second (B) derivative spectra at the Ni K-edge for reference materials (Ni foil and [NiF2]), formally Ni(II) complexes ([Ni(X)2(PPh3)2], X = Cl, Br, I; [Ni(Cl)(L3)]) and the NO complexes investigated here. The derivative spectra were generated using 5% Savitzky-Golay filter. SUP - 12

First Derivative of XAS intensity (EY/I0) 1.3 0.3-840 845 850 855 Photon Energy, ev [Ni(NO)(Br)(PPh 3 ) 2 ] -0.7-1.2 A Ni L 3 -edge [Ni(Cl)(L3)] [Ni(NO)(L3)] [Ni(Br) 2 (PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] [NiF 2 ] First Derivative of XAS intensity (EY/I0) 0.5 0.3 0.1 855 860 Photon Energy, ev 865 870 - - B Ni L 2 -edge [Ni(Cl)(L3)] [Ni(NO)(L3)] [Ni(NO)(Br)(PPh 3 ) 2 ] [Ni(Br) 2 (PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] [NiF 2 ] -1.7 - Second Derivative of XAS intensity (EY/I0) 0.7 0.5 0.3 0.1-0.1840 845 850 [Ni(NO)(Br)(PPh 855 3 ) 2 ] -0.3-0.5-0.7-0.9 C [Ni(Cl)(L3)] [Ni(NO)(L3)] Photon Energy, ev [Ni(Br) 2 (PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] [NiF 2 ] Second Derivative of XAS intensity (EY/I0) 0.1 [Ni(NO)(Cl)(PPh 855 860 865 870 3 ) 2 ] [Ni(NO)(Br)(PPh 3 ) 2 ] -0.1 - -0.3 D Photon Energy, ev [Ni(Cl)(L3)] [Ni(NO)(L3)] [Ni(Br) 2 (PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] [NiF 2 ] -1.1 - Fig. S14 First (A and B) and second (C and D) derivative spectra at the Ni L3 and L2-edges, respectively, for reference materials (Ni foil and [NiF2]), formally Ni(II) complexes ([Ni(X)2(PPh3)2], X = Cl, Br, I; [Ni(Cl)(L3)]) and the NO complexes investigated here. The derivative spectra were generated using 5% Savitzky-Golay filter. SUP - 13

First Derivative of XAS intensity (FY/I0) 0.10 8 6 4 2 0 2817 2822 2827-2 -4 A Photon Energy, ev Cl K-edge [Ni(Cl)(L3)] Cs 2 [CuCl 4 ] NaCl Second Derivative of XAS intensity (FY/I0) -6 14 09 B 04-01 2817 2822 2827-06 -11-16 -21 Photon Energy, ev [Ni(Cl)(L3)] Cs 2 [CuCl 4 ] NaCl Fig. S15 First (A) and second (B) derivative spectra at the Cl K-edge for the free ligand salt (NaCl), the reference compound (Cs2[CuCl4]), formally Ni(II) complexes ([Ni(Cl)2(PPh3)2]; [Ni(Cl)(L3)]) and the NO complex with a chloride ligand. The derivative spectra were generated using 5% Savitzky-Golay filter. SUP - 14

First Derivative of XAS intensity (FY/I0) 0.3 0.1 2141 2143 2145 2147-0.1 A P K-edge [Ni(NO)(Br)(PPh 3 ) 2 ] [Ni(Br) 2 (PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] PPh 3 PCy 3 Second Derivative of XAS intensity (FY/I0) - 0.14 9 4-6 -0.11-0.16-1 B Photon Energy, ev -1 2141 2143 2145 2147 Photon Energy, ev [Ni(NO)(Br)(PPh 3 ) 2 ] [Ni(Br) 2 (PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] PPh 3 PCy 3 Fig. S16 First (A) and second (B) derivative spectra at the P K-edge for the free ligands (PR3, R=Ph, Cy), formally Ni(II) complexes ([Ni(X)2(PPh3)2], X=Cl, Br, I) and the NO complexes with phosphane ligands. The derivative spectra were generated using 5% Savitzky-Golay filter. SUP - 15

calculated oscillator strength x 1000 0.7 0.5 0.3 A [Ni(NO)(L3)] [Ni(Cl)(L3)] [Ni(NO)(Br)(PPh 3 ) 2 ] [Ni(I) 2 (PPh 3 ) 2 ] 0.1 [Ni(Br) 2 (PPh 3 ) 2 ] 8195 8197 8199 8201 8203 8205 8207 8209 calculated Ni 1s excitation energies calculated oscillator strength x 1000 3.0 B 2.5 2.0 1.5 [Ni(Cl)(L3)] 0.5 2740 2742 2744 2746 2748 2750 calculated Cl 1s excitation energies calculated oscillator strength x 1000 9.0 8.0 C 7.0 6.0 5.0 4.0 3.0 [Ni(NO)(Br)(PPh 3 ) 2 ] 2.0 [Ni(I) 2 (PPh 3 ) 2 ] [Ni(Br) 2 (PPh 3 ) 2 ] 2076 2078 2080 2082 2084 calculated P 1s excitation energies Fig. S17 Calculated core-level excited state spectra at the Ni K (A), Cl K (B), and P K (C) edges for the first 100 excited states at BP86/TZVP level of theory. Fig. S18 Comparison of the experimental [Ni(NO)(L3)] Ni K-edge XAS with that calculated by TD-DFT using the broken-symmetry formalism. The first 100 calculated states were calculated using the B3LYP/decontracted def2-tzvp functional-basis combination. A shift of -159.8 ev was applied to the calculated spectrum. The generated spectra utilize a 1.5 ev linewidth. SUP - 16

Fig. S19 Comparison of the experimental [Ni(NO)(L3)] Ni K-edge XAS with that calculated by TD-DFT using the closed-shell formalism. The first 100 calculated states were calculated using the B3LYP/decontracted def2-tzvp functional-basis combination. A shift of -159.8 ev was applied to the calculated spectrum. The generated spectra utilize a 1.5 ev linewidth. Fig. S20 Comparison of the experimental [Ni(NO)(L3)] Ni K-edge XAS with that calculated by TD-DFT using the broken-symmetry (red) and closed-shell (blue) formalisms. The first 100 calculated states were calculated using the B3LYP/decontracted def2-tzvp functional-basis combination. A shift of -159.8 ev was applied to the calculated spectra. The generated spectra utilize a 1.5 ev linewidth. SUP - 17

Fig. S21 Cyclic voltammetry of a 2 mm solution of [Ni(NO)(L3)] in THF at various scan rates with 0.1 M TBAP as supporting electrolyte. A glassy carbon working electrode was used along with a platinum working electrode and Ag wire reference electrode. SUP - 18

Table S1 X-ray crystallographic data for and [Ni(NO)(Br)(PPh 3 ) 2. [Ni(NO)(Br)(PPh 3 ) 2 ] CCDC deposit number 1447248 1447249 Empirical Formula C36H30ClNNiOP2 C36H30BrNNiOP2 Formula Weight 648.74 693.19 Crystal System monoclinic triclinic Space Group P21/a (#14) P 1 (#2) a / Å 12.473(2) 9.625(2) b / Å 18.962(3) 14.861(3) c / Å 13.575(2) 22.744(5) α / 79.558(4) β / 97.870(2) 85.900(6) γ / 89.993(7) V / Å 3 318(9) 319(12) Z 4 4 Dcalc / g cm 3 1.355 1.443 μ(mo Kα) / cm 1 8.241 19.938 2θmax / 55.0 55.0 Temperature / C 77 95 Exposure Rate / sec 48 64 Reflections collected 25418 24664 Unique reflections 7271 14160 R (int) 184 233 No. of obserb. (All refl.) 7271 14160 No. of variables 379 757 R1 (I > 2.0 σ(i)) 327 471 wr2 (All reflections) 884 0.1450 Good. of fit indicator 44 0.913 Max/min peak, / e Å 3 9 / 0.33 2.83 / 0.73 R1 = Σ Fo - Fc / Σ Fo ; wr2 = [(Σ w( (Fo 2 - Fc 2 ) 2 )/ Σ w( Fo 2 ) 2 ] 1/2 SUP - 19

Table S2 X-ray crystallographic data for [Ni(NO)(L3)] and [Ni(Cl)(L3)] [Ni(NO)(L3)] [Ni(Cl)(L3)] CCDC deposit number 1447250 1447251 Empirical Formula C30H52BN7NiO C30H52BClN6Ni Formula Weight 596.30 601.74 Crystal System orthorhombic monoclinic Space Group Cmc2 1 (#36) P21/n (#14) a / Å 16.247(3) 9.5570(8) b / Å 10.3372(17) 17.3659(8) c / Å 19.855(3) 2069(13) α / β / 99.636(3) γ / V / Å 3 3334.6(10) 3306.3(4) Z 4 4 Dcalc / g cm 3 1.188 1.209 μ(mo Kα) / cm 1 6.147 6.956 2θmax / 55.0 55.0 Temperature / C 94 77 Exposure Rate / sec 40 48.0 Reflections collected 12785 26308 Unique reflections 3889 7556 R (int) 140 221 No. of obserb. (All refl.) 3889 7556 No. of variables 199 352 R1 (I > 2.0 σ(i)) 462 484 wr2 (All reflections) 0.1283 0.1420 Good. of fit indicator 80 80 Max/min peak, / e Å 3 9 / 1 93 / 0.73 R1 = Σ Fo - Fc / Σ Fo ; wr2 = [(Σ w( (Fo 2 - Fc 2 ) 2 )/ Σ w( Fo 2 ) 2 ] ½ SUP - 20

Table S3 BP86-optimized coordinates of [Ni(NO)(L3)]. x y z Ni -1.511620 17713-29770 O -4.330890 48965-59930 N -0.352350-39260 -1.348540 N 00757-0.952400-1.122290 N -0.332620 1.679428-49770 N 18987 1.429375-53240 N -0.382030-24210 1.553147 N 0.975379-0.513430 1.371276 N -3.156530 35528-49460 C -1.891990-2.261360-2.962090 C -0.532100-1.890910-2.386160 C 0.726715-2.351590-2.819410 C 1.678103-1.745070-2.001570 C -1.849840 3.702841-0.500030 C -95690 3.009527-46470 C 0.772504 3.608150-0.580380 C 1.712282 2.586826-55530 C 3.663610 2.419871-2.028350 C 3.756310 4.000985-50610 C -1.954070-1.367810 3.409015 C -0.581930-97750 2.806338 C 68970-1.288450 3.425318 C 1.636465-0.909370 2.496972 B 1.518419-18580 04457 H 2.719171-33400 22101 H 0.924562-3.040990-3.631540 H 0.982417 4.658414-0.745600 H 4.762150 2.425388-2.096200 H 3.273487 3.208029-2.690250 H 3.300731 1.453297-2.403770 H 3.392958 4.841926-60420 H 4.855281 4.005959-98790 H 3.455858 4.180316 0.991371 H 50909-1.660550 4.426120 C 3.582625 0.521117 3.189083 H 3.173768 99095 4.195313 H 4.680096 0.571250 3.249495 H 3.236280 1.333760 2.535203 C 3.646624-1.985750 3.564985 H 4.743069-1.942430 3.639084 H 3.239856-1.896180 4.583405 H 3.367222-2.974950 3.174184 C 3.577938-3.081880-44550 H 3.152316-4.035650-1.391380 H 4.672744-3.185170-09390 H 3.217326-2.903240-21520 SUP - 21

C 3.724043-2.172120-3.406490 H 4.820676-2.250690-3.375140 H 3.334916-3.109050-3.832540 H 3.456537-1.351810-4.087850 C -1.708680-3.202180-4.169210 H -1.199590-4.134230-3.883280 H -2.694640-3.471280-4.575510 H -1.130250-2.723020-4.973130 C -2.733120-3.004020-1.898800 H -2.234010-3.934600-1.590500 H -2.882510-2.388040-03640 H -3.719920-3.263590-2.310250 C -2.630230-0.993920-3.445820 H -3.621880-1.261320-3.841030 H -2.767220-71250 -2.631570 H -2.063020-97810 -4.247440 C -1.655580 5.220028-89250 H -1.150330 5.450667-1.639240 H -2.637560 5.714961-0.703200 H -68910 5.658932 0.131314 C -2.613600 3.477579 24037 H -2.760700 2.408745 26253 H -2.057850 3.907256 1.670878 H -3.600970 3.960973 0.779215 C -2.673290 3.168536-1.692600 H -2.164530 3.383929-2.644400 H -2.820100 2.083226-1.624780 H -3.661600 3.651449-1.714740 C -2.759370-52540 3.500232 H -2.252630 67046 4.160233 H -2.874830 13596 2.514408 H -3.761160-50440 3.911420 C -1.797280-1.933470 4.834531 C -2.715540-2.407370 2.557183 H -2.849490-2.061510 1.524397 H -2.168760-3.361190 2.527824 H -3.710400-2.595110 2.989404 C 3.174326-1.932830-1.991710 H 3.626893-07850 -1.602680 C 3.134972-56650 2.656880 H 3.582467-0.990160 1.659990 C 3.213452 2.661373-0.573020 H 3.637824 1.855562 45799 SUP - 22

Table S4 M06-L-optimized coordinates of [Ni(NO)(L3)]. x y z Ni -1.723330-0.337370-0.317000 O -4.450110-24320 -98310 N -60380 1.566171-0.551470 N 69081 1.566633-42650 N -26980-0.520360 1.600583 N 88476-0.159080 1.580397 N 37886-1.265610-1.217730 N 1.261751-30410 -0.790580 N -3.329830-37710 -38700 C -2.347130 3.224848-1.343370 C -0.964980 2.816842-0.916620 C 0.172254 3.623954-33410 C 1.194166 2.799971-0.397150 C -2.277750-1.291490 3.299535 C -0.914120-29880 2.869790 C 19323-54430 3.668810 C 1.221383-22980 2.817906 C 2.821458 28101 4.620008 C 3.596020-12310 2.737537 C -38670-2.940820-2.844570 C 68324-2.214870-2.131670 C 1.642693-2.392210-2.292560 C 2.248699-1.498400-1.427040 B 1.355355 87126 68618 H 2.498798 0.525479 82803 H 49139 4.673434-58930 H 0.308114-19820 4.729048 H 3.853445 0.721615 4.818499 H 2.608260-45180 5.240012 H 2.169326 1.238100 4.947199 H 3.381218-1.923620 3.299850 H 4.632374-0.732550 2.940419 H 3.510272-1.246380 1.676903 H 2.147483-3.078910-2.950340 C 4.390022-2.557050-85500 H 4.363015-3.360840-1.425160 H 5.438022-2.356770-51570 H 3.908226-2.926130 19751 C 4.409378-47760 -2.506280 H 5.454510-00670 -2.308330 H 4.393715-1.642370-3.256280 H 3.934388 30758-2.942850 C 3.555590 2.636267-1.226080 H 3.334228 3.119984-2.179650 H 4.598299 2.848107-0.978870 H 3.452190 1.561429-1.368150 SUP - 23

C 2.813243 4.647275 42067 H 3.848858 4.869090 0.303978 H 2.594176 5.178943-86810 H 2.171203 5.055005 23063 C -2.348620 4.707482-1.708280 H -1.671880 4.914002-2.539530 H -3.349920 5.020718-2.005300 H -2.039020 5.326597-64410 C -2.760520 2.404465-2.564230 H -2.053900 2.547525-3.384530 H -2.784620 1.338789-2.328800 H -3.751240 2.700363-2.912340 C -3.325650 2.988576-0.193810 H -3.333800 1.939352 0.107056 H -3.048920 3.580122 81054 H -4.338620 3.268824-88650 C -2.248000-1.646680 4.784301 H -1.963180-0.788300 5.395224 H -3.232400-1.981270 5.112524 H -1.535710-2.449210 4.985509 C -2.670220-2.527560 2.492189 H -2.713660-2.299430 1.424982 H -1.942160-3.329670 2.631620 H -3.648330-2.897850 2.802240 C -3.286440-0.167840 3.065384 H -3.023580 0.717862 3.647057 H -3.310930 0.123229 2.012838 H -4.289600-83090 3.357837 C -1.695120-3.694110-1.827420 H -93220-4.418840-1.275490 H -2.139930-3.014700-99340 H -2.499750-4.232410-2.331360 C -35410-3.942480-3.825340 H 0.381807-4.681320-3.310360 H -25350-4.476500-4.354830 H 0.388751-3.443560-4.569310 C -1.690040-1.937160-3.621610 H -2.134140-1.193220-2.959330 H -84150-1.402630-4.355960 H -2.494680-2.449450-4.151980 C 2.627749 3.148059-0.130050 H 2.918327 2.659409 06977 C 3.719846-1.296540-1.222250 H 3.853904-0.507260-79180 C 2.646263 0.109312 3.143179 H 2.920431 00956 2.568211 SUP - 24

Table S5 B3LYP-optimized coordinates of [Ni(NO)(L3)]. x y z Ni -1.516010 70440-86430 O -4.429760 11218-0.117010 N -41360-84610 1.396143 N 0.917899-05370 1.231952 N -27340-0.733300-1.567360 N 0.907776-18100 -1.273850 N -19400 1.870672-42160 N 83991 1.490984-22530 N -3.259980 52290-0.110680 C -2.050920-1.683280 3.082485 C -70070-1.352540 2.538004 C 0.557181-1.705540 3.110406 C 1.542009-1.224520 2.262949 C -2.038420-1.853390-3.174750 C -68950-1.603790-2.562040 C 0.525153-2.259240-2.895450 C 1.501353-1.750400-2.052890 C 3.166635-3.624790-2.232120 C 3.852404-1.266650-2.840470 C -1.512610 4.046882 0.107932 C -57600 3.211414-92060 C 36398 3.692113-0.335970 C 1.860552 2.582369-23210 B 1.486177-02150 -88460 H 2.672306-78410 -87330 H 0.713795-2.247990 4.025044 H 60985-3.014410-3.648580 H 4.203463-3.899270-2.024110 H 2.958207-3.865110-3.277420 H 2.522171-4.246610-1.609070 H 3.611185-1.420210-3.895640 H 4.902288-1.529430-2.687520 H 3.732775-05150 -2.617390 H 1.334699 4.718350-49980 C 3.759180 3.759562-1.554090 H 3.638053 4.685040-0.986740 H 4.811320 3.675414-1.833530 H 3.168829 3.843115-2.467760 C 4.194377 2.439219 0.553390 H 5.248652 2.342333 82775 H 4.080006 3.333781 1.170914 H 3.917770 1.575026 1.156899 C 3.509853-06570 3.574839 H 3.035562-72080 4.522197 H 4.592122-84980 3.703003 H 3.264053 35128 3.358577 SUP - 25

C 3.442892-2.794030 2.739381 H 4.528583-2.869350 2.836077 H 2.999830-3.150130 3.671522 H 3.123760-3.464380 1.939059 C -1.911550-2.530160 4.360726 H -1.375700-1.991710 5.145051 H -2.903360-2.780200 4.742236 H -1.383470-3.465660 4.164755 C -2.816370-0.393720 3.433105 H -2.273190 0.188822 4.180693 H -2.963970 35101 2.556338 H -3.799160-41430 3.841899 C -2.844220-2.504740 2.049419 H -3.028000-1.935460 1.140450 H -2.301360-3.412060 1.775640 H -3.810080-2.798510 2.466429 C -1.895040-2.745840-4.420610 H -1.465810-3.718210-4.171580 H -2.879430-2.921410-4.858690 H -1.265870-2.277270-5.180610 C -2.701530-0.530310-3.598080 H -2.850340 0.135334-2.749370 H -2.089370-07880 -4.336750 H -3.678290-0.729310-4.045640 C -2.932260-2.590170-2.156360 H -2.457940-3.514670-1.819850 H -3.126150-1.972690-1.281400 H -3.891820-2.845280-2.611970 C -2.464240 3.874696-92890 H -1.971880 4.184517-2.017880 H -2.785120 2.840627-1.211040 H -3.353980 4.494292-0.958510 C -1.133660 5.535874 10836 H -0.706980 5.911714-0.721000 H -2.028210 6.122476 30689 H -13630 5.712414 12155 C -2.214550 3.660605 1.424668 H -2.500660 2.610058 1.447938 H -1.556730 3.853609 2.275441 H -3.118300 4.260504 1.550254 C 3.032202-1.340590 2.449838 H 3.520150-32240 1.525701 C 3.338353 2.542326-0.719230 H 3.528996 1.648929-1.317150 C 2.955457-2.133220-1.942320 H 3.260974-1.957810-0.910040 SUP - 26

Table S6 B3LYP-D-optimized coordinates of [Ni(NO)(L3)]. x y z Ni -1.540420 0.307481-97960 O -4.314250 0.551973-96750 N -35820-79880 1.367900 N 0.915489-80950 1.167593 N -42260-73120 -1.577650 N 98604-0.759380-1.322510 N -0.179600 1.853685-80940 N 1.133911 1.473601-0.114010 N -3.159730 54329-97020 C -2.061430-1.667290 3.019615 C -71410-1.407190 2.469662 C 0.548334-1.887500 2.972506 C 1.533349-1.407870 2.121214 C -2.108540-1.793200-3.101850 C -0.717300-1.556820-2.547040 C 61298-2.232840-2.900240 C 1.462599-1.718040-2.092280 C 3.132835-3.554190-2.479860 C 3.830851-1.134510-2.727850 C -1.485730 3.999081 0.105954 C -05550 3.188045 40393 C 1.111643 3.667605 96281 C 1.935720 2.557321-02430 B 1.498657-23270 -0.105870 H 2.679433-0.136890-0.122060 H 98247-2.499790 3.843108 H 0.571995-3.002080-3.642680 H 4.167414-3.849660-2.291310 H 2.945020-3.645610-3.552410 H 2.478083-4.254540-1.959490 H 3.627402-1.145260-3.801350 H 4.877687-1.407910-2.571960 H 3.688628-0.118650-2.360770 H 1.429801 4.690400 0.188444 C 3.909972 2.759257-1.514570 H 3.684120 3.784733-1.818230 H 4.987888 2.601004-1.600650 H 3.408718 2.087365-2.212500 C 4.077244 3.500588 0.907061 H 5.165637 3.416643 68388 H 3.811236 4.531295 59745 H 3.753442 3.304403 1.931397 C 3.669230-0.384820 2.923744 H 3.339402-0.356280 3.965277 H 4.758655-66050 2.906908 H 3.389385 0.560771 2.456466 SUP - 27

C 3.423593-2.915720 2.797383 H 4.505375-3.050430 2.728198 H 3.140525-2.973920 3.851394 H 2.940971-3.741060 2.271323 C -1.965200-2.505590 4.305064 H -1.395660-1.985320 5.078220 H -2.967280-2.696910 4.693634 H -1.488300-3.469610 4.116918 C -2.763230-0.337330 3.348936 H -2.203250 19426 4.103631 H -2.851460 92288 2.465509 H -3.767190-0.527060 3.736558 C -2.883810-2.453590 1.981788 H -3.004480-1.880060 66422 H -2.387130-3.392050 1.726412 H -3.874810-2.684390 2.378694 C -2.025140-2.687010-4.350290 H -1.604770-3.666170-4.112760 H -3.025880-2.844510-4.756730 H -1.409540-2.228230-5.127190 C -2.769350-59870 -3.493020 H -2.852270 09336-2.639030 H -2.184260 48675-4.262600 H -3.772570-39240 -3.886610 C -2.957640-2.516680-2.038100 H -2.478990-3.449320-1.732120 H -3.079250-1.897560-1.152930 H -3.947380-2.750950-2.436020 C -2.327510 3.751465-1.161770 H -1.773120 4.057541-2.052210 H -2.584800 2.699388-1.273620 H -3.252860 4.329906-1.119710 C -1.146090 5.497776 0.181215 H -01830 5.830532-0.705290 H -2.068140 6.078107 50500 H -0.540280 5.727649 60301 C -2.282350 3.625209 1.372121 H -2.530830 2.564820 1.393880 H -1.699980 3.854150 2.267757 H -3.211720 4.197078 1.412250 C 3.026311-1.569790 2.184792 H 3.406419-1.554930 1.162896 C 3.437535 2.509962-70860 H 3.760137 1.509161 14457 C 2.910804-2.118350-1.992990 H 3.182492-2.091920-0.935610 SUP - 28

Table S7 B3LYP-CAM-optimized coordinates of [Ni(NO)(L3)]. x y z Ni -1.342740-0.130000 53463 O -4.253750 35074 66327 N -73270 1.106204-1.207550 N 41948 0.759186-1.223560 N -0.161050 34903 1.787095 N 0.979049 0.757295 1.262835 N -0.104660-1.695070-09090 N 1.158810-1.419050 13289 N -3.100140-13730 94117 C -1.835110 2.456538-2.651180 C -94530 1.860257-2.285690 C 93729 1.983069-3.008430 C 1.641540 1.261445-2.311950 C -1.511150 0.526585 3.876581 C -19780 0.914126 2.905343 C 0.525258 1.932800 3.058526 C 1.383509 1.815128 1.980064 C 1.899804 3.737294 0.513926 C 3.158683 3.449811 2.668346 C -1.452720-3.728430-0.998860 C -12010-3.017960-0.506850 C 0.990122-3.603630-0.106010 C 1.828585-2.561600 36938 B 1.609579 58114 32519 H 2.802414 0.128706 61990 H 45727 2.530704-3.919410 H 0.583072 2.656546 3.853182 H 2.699315 4.338864 77197 H 1.204688 4.410605 18802 H 1.362292 3.240868-92100 H 2.450936 4.089837 3.199422 H 3.956109 4.088907 2.287625 H 3.591804 2.752110 3.384890 H 1.224493-4.651120-64030 C 3.024476-2.384570 2.390488 H 2.330510-3.107800 2.820544 H 3.984360-2.501980 2.895752 H 2.632252-1.389250 2.599641 C 3.850220-3.983000 57010 H 4.853510-3.973910 83135 H 3.293680-4.778670 1.154156 H 3.929403-4.229580-01890 C 3.048997-0.310600-3.585680 H 2.507041-0.121490-4.513890 H 4.068332-06050 -3.839790 H 2.561850-1.141790-3.074210 SUP - 29

C 3.696893 2.119582-3.440110 H 4.704634 1.857224-3.764370 H 3.126648 2.387249-4.330240 H 3.757867 3.000672-2.801400 C -1.638560 3.528978-3.725430 H -1.202150 3.113053-4.633800 H -2.601710 3.967171-3.989980 H -0.988600 4.329657-3.370550 C -2.736320 1.353404-3.222390 H -2.252360 64258-4.070010 H -2.956900 0.595255-2.474050 H -3.680840 1.777078-3.568390 C -2.486170 3.114552-1.431040 H -2.686180 2.396514-40630 H -1.839780 3.894041-24200 H -3.432390 3.575014-1.720890 C -2.593830 1.611809 3.898053 H -3.041300 1.741873 2.911435 H -3.387790 1.346607 4.598183 H -2.175430 2.569598 4.211927 C -94060 07133 5.278942 H -87330-0.326180 5.290495 H -85900 1.358435 5.623570 H -1.658110 82239 5.988561 C -2.118530-31240 3.526576 H -2.596620-38750 2.549275 H -1.352880-1.606890 3.534270 H -2.875590-87650 4.267967 C -2.570050-3.612360 43126 H -2.247630-4.039690 0.994038 H -2.856120-2.577870 20862 H -3.453170-4.156890-96150 C -1.138690-5.211400-1.203980 H -71520-5.699550-66530 H -2.014260-5.717160-1.613320 H -0.315990-5.350900-1.906090 C -1.901080-3.151030-2.346470 H -2.134320-2.088350-2.283330 H -1.116030-3.283880-3.093040 H -2.791450-3.674940-2.697050 C 3.049752 0.946158-2.711330 H 3.625642 0.725986-1.811980 C 3.176825-2.632240 86176 H 3.809225-1.848970 64891 C 2.476228 2.727368 1.514534 H 3.219569 2.124059 0.989708 SUP - 30

Table S8: Input keywords used for calculating core-level excited state spectra within ADF at BP86/TZ2P level #!/bin/csh ####################################################################### $ADFBIN/adf << eor title complex Charge 0 2 unrestricted atoms cartesian coords Ni x y z end integration 5.0 XC GGA BP86 END Basis Type TZ2P Core None End excitation allowed lowest 100 end relativistic scalar zora modifyexcitation UseOccupied <irred.rep> <MO number(s)> subend UseScaledZORA end eprint orbpoper -500 500 end end input eor ###################################################################### SUP - 31