SUPPLEMENTARY INFORMATION

Transcription

1 SUPPLEMENTARY INFORMATION Isolation of a radical dianion of nitrogen oxide, (NO) 2- William J. Evans 1 *, Ming Fang 1, Jefferson E. Bates 1, Filipp Furche 1, Joseph W. Ziller 1, Matthew D. Kiesz 2 and Jeffrey I. Zink 2 1 Department of Chemistry, University of California, Irvine, California, USA. 2 Department of Chemistry and Biochemistry, University of California, Los Angeles, California, USA. *To whom correspondence should be addressed. wevans@uci.edu nature chemistry 1

2 supplementary information General Experimental Procedures The syntheses and manipulations described below were conducted under argon or nitrogen with rigorous exclusion of air and water using glovebox, vacuum line, and Schlenk techniques. Potassium was purchased from Aldrich, washed with hexanes, and scraped to provide shiny pieces before use. NO (98.5%) was purchased from Aldrich. The NO x impurities were removed by passing NO through a dry ice/acetone cold bath. Lower boiling point impurities were removed under reduced pressure while NO was frozen at -196 C. 15 NO (98%) was purchased from Cambridge Isotope Laboratories and purified as above. Compounds 1 and 2 were synthesized following published procedures 1. Solvents were dried over columns containing Q-5 and molecular sieves. NMR solvents were dried over sodium-potassium alloy, degassed, and vacuum transferred prior to use. 1 H and 13 C NMR spectra were obtained on a Bruker DRX500 MHz spectrometer at 25 C. IR samples were prepared as KBr pellets and the spectra were obtained on a Varian 1000 FT-IR system. Elemental analyses were performed on a Perkin-Elmer 2400 CHNS elemental analyzer. Electron paramagnetic resonance spectra were collected using a Bruker EMX spectrometer equipped with an ER041XG microwave bridge. The magnetic field was calibrated with DPPH and all experiments were conducted at room temperature. SIMPOW6 (ref. 2) developed by Professor Nilges at University of Illinois was used to simulate the EPR spectra. Raman spectra were recorded using a Jobin-Yvon HR 640 triple monochromator equipped with a CCD detector (Roper Scientific Model ) operating at -120 C. A Coherent I-300C krypton ion laser operating between 20 and 35 mw was used as the excitation source. The sample (~10 mg) was sealed in a quartz EPR tube (4 mm OD) and chilled nitrogen 2 nature chemistry

3 supplementary information was blown on the sample, obtaining temperatures of 5 to 10 C while irradiating. Compound 3 was observed by exciting at 457 nm, although the resonant maxima of the compound cannot be determined. X-ray Data Collection, Structure Solution and Refinement For all the structures, the APEX2 (ref. 3) program package was used to determine the unit-cell parameters and for data collection (15 s/frame scan time for a hemisphere of diffraction data for compound 3 2THF; 30 s/frame scan time for a sphere of diffraction data for compound 4 3toluene). The raw frame data was processed using SAINT 4 and SADABS 5 to yield the reflection data file. Subsequent calculations were carried out using the SHELXTL 6 program. The structures were solved by direct methods and refined on F 2 by full-matrix least-squares techniques. The analytical scattering factors 7 for neutral atoms were used throughout the analysis. Hydrogen atoms were included using a riding model. For compound 3 2THF, the molecule was located about an inversion center. Atoms N(3) and O(3) were disordered. The disorder was modeled using various partial site-occupancy values for the nitrogen and oxygen atoms in addition to full occupancy for each. Both isotropic and anisotropic models were tested. The best refinement was obtained using the a disordered model with atoms N(3) and O(3) assigned siteoccupancy-factors of 0.50 and isotropic thermal parameters. Although the composition of the atoms labeled N(3) and O(3) could not be unambiguously determined from the x- ray data, other supporting data suggests this unit is the dianion (NO) 2-. There were two molecules of THF solvent present. nature chemistry 3

4 supplementary information Computational Details The structure of 3 was initially optimized using the TPSSH 8 hybrid meta-gga functional and split valence basis sets with polarization functions on non-hydrogen atoms (SV(P)) 9. TPSSH was chosen due to its established performance for transition metal 10,11 and lanthanide 1. Relativistic small-core pseudopotentials 12 were employed for Y. Fine quadrature grids (size m4) 13 were used throughout. The total spin expectation value of the spin-unrestricted Kohn-Sham reference was 0.76 a.u. at the minimum structure. Vibrational frequencies were computed at the TPSSH/SV(P) level 14 and scaled by a factor of 0.95 to account for anharmonicity and basis set incompleteness1 1. No imaginary vibrational frequencies were found. Natural population analyses 15 and plots were also obtained at the TPSSH/SV(P) level. Since the canonical unrestricted Kohn- Sham orbitals showed strong spin polarization, natural orbitals of the total spin density matrix were used for the molecular orbital plots; the contour values were 0.03 for molecular orbitals and for the spin density. The structural parameters reported in the text are the result of re-optimization using larger triple-zeta valence basis sets with two sets of polarization functions (def2-tzvp) 16. The differences between the SV(P) and the TZVP structures were found to be small, typically amounting to 0.01 Å in bond lengths or less. All computations were performed using the TURBOMOLE program package nature chemistry

5 supplementary information References 1. Evans, W. J. et al., Isolation of dysprosium and yttrium complexes of a threeelectron reduction product in the activation of dinitrogen, the (N2) 3- Radical. J. Am. Chem. Soc. 131, (2009). 2. Nilges, M. J., Mattson, K. J. & Belford, R. L., ESR Spectroscopy in Membrane Biophysics, Biological Magnetic Resonance, Hemminga, M. A. & Berliner, L. Eds. (Springer, New York, 2006), vol. 27, pp APEX2 Version Bruker AXS, Inc.; Madison, WI SAINT Version 7.46a, Bruker AXS, Inc.; Madison, WI Sheldrick, G. M., SADABS, Version 2008/1, Bruker AXS, Inc.; Madison, WI Sheldrick, G. M., SHELXTL, Version 6.12, Bruker AXS, Inc.; Madison, WI International Tables for X-Ray Crystallography, (Kluwer Academic Publishers, Dordrecht, 1992), vol. C. 8. Staroverov, V. N., Scuseria, G. E., Tao, J. & Perdew, J. P. Comparative assessment of a new nonempirical density functional: molecules and hydrogenbonded complexes. J. Chem. Phys. 119, (2003). 9. Schäfer, A., Horn, H. & Ahlrichs, R. Fully optimized contracted Gaussian basis sets for atoms Li to Kr. J. Chem. Phys. 97, (1992). 10. Furche, F. & Perdew, J. P. The performance of semilocal and hybrid density functionals in 3d transition-metal chemistry. J. Chem. Phys. 124, (1) (27) (2006). nature chemistry 5

6 supplementary information 11. Waller, M. P., Braun, H., Hojdis, N. & Bühl, M. Geometries of second-row transition-metal complexes from density-functional theory. J. Chem. Theor. Comput. 3, (2007). 12. Andrae, D., Häussermann, U. & Dolg, M. Energy-adjusted ab initio pseudopotentials for the second and third row transition elements. Theor. Chim. Acta 77, (1990). 13. Treutler, O. & Ahlrichs, R. Efficient molecular numerical integration schemes. J. Chem. Phys. 102, (1995). 14. Deglmann, P., Furche, F. & Ahlrichs, R. An efficient implementation of second analytical derivatives for density functional methods. Chem. Phys. Lett. 362, (2002). 15. Reed, A. E., Weinstock, R. B. & Weinhold, F. Natural population analysis. J. Chem. Phys. 83, (1985). 16. Weigend, F. & Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Phys. Chem. Chem. Phys. 18, (2005). 17. TURBOMOLE V6-0, TURBOMOLE GmbH, Karlsruhe, 2008, 6 nature chemistry

7 supplementary information Figure S1 Raman spectra of {[(Me 3 Si) 2 N] 2 (THF)Y} 2 ( - 2 : 2 -NO), 3, and its 15 N labeled analogue, 3-15 NO. (Data were collected with 457 nm laser.) Figure S2 Thermal ellipsoid plot of {[(Me 3 Si) 2 N] 2 Y} 4 ( 3 -ON=NO) 2 (THF) 2, 4, drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. nature chemistry 7

8 supplementary information Table S1 Selected bond distances (Å) and angles (º) in 3 and 4. 3 N(3)-O(3) 1.390(4) Y(1)-O(3) 2.293(3) Y(1)-N(1) 2.269(2) Y(1)-O(3)-Y(1') 142.6(2) Y(1)-N(2) 2.251(2) Y(1)-N(3)-Y(1') 142.3(2) Y(1)-N(3) 2.269(5) N(3)-Y(1)-O(3) 35.5(1) Y(1)-O(1) 2.358(1) 4 O(1)-N(5) 1.392(2) O(1)-Y(1)-O(1') 64.96(6) O(3)-N(6) 1.335(2) O(1')-Y(1)-N(6') 50.79(6) N(5)-N(6) 1.257(3) N(5)-O(1)-Y(1) 139.8(1) Y(1)-O(1) 2.264(2) N(5)-O(1)-Y(1') 104.3(1) Y(1)-O(1') 2.345(2) Y(1)-O(1)-Y(1') (6) Y(1)-N(1) 2.233(2) N(6)-N(5)-O(1) 105.6(2) Y(1)-N(2) 2.224(2) N(5)-N(6)-O(3) 113.2(2) Y(1)-N(6') 2.559(2) N(5)-N(6)-Y(1') 98.2(4) Y(2)-O(2) 2.301(2) O(3)-N(6)-Y(1') 147.0(4) Y(2)-O(3) 2.147(2) N(6)-O(3)-Y(2) 158.4(4) Y(2)-N(3) 2.225(2) Y(2)-N(4) 2.212(2) 8 nature chemistry

9 supplementary information Table S2 Calculated spin density ρ_s(n) (a.u.) at the nitrogen nucleus of the (N 2 ) 3- ligand in 2 and the (NO) 2- ligand in 3, as well as calculated and experimental isotropic hyperfine coupling constants A (MHz) of the same nitrogen nucleus. The ligand nitrogen and oxygen TZVP basis sets were uncontracted. Hyperfine coupling constants were evaluated using the Fermi contact expression. Compound ρ_s(n) A( 14 N) calc A( 14 N) exp A( 15 N) calc ( 15 N) exp nature chemistry 9

10 supplementary information Table S3 Crystal data and structure refinement for 3 2THF, {[(Me 3 Si) 2 N] 2 (THF)Y} 2 ( - 2 : 2 -NO) 2C 4 H 8 O. Empirical formula C 32 H 88 N 5 O 3 Si 8 Y 2 2(C 4 H 8 O) Formula weight Temperature 93(2) K Wavelength Å Crystal system Monoclinic Space group P2 1 /c Unit cell dimensions a = (4) Å = 90. b = (9) Å = (5). c = (4) Å = 90. Volume (19) Å 3 Z 2 Density (calculated) Mg/m 3 Absorption coefficient mm -1 F(000) 1218 Crystal color light green Crystal size 0.28 x 0.22 x 0.21 mm 3 Theta range for data collection 2.45 to Index ranges -14 h 14, -31 k 31, -14 l 14 Reflections collected Independent reflections 7104 [R(int) = ] Completeness to theta = % Absorption correction Semi-empirical from equivalents Max. and min. transmission and Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 7104 / 0 / 282 Goodness-of-fit on F Final R indices [I>2sigma(I) = 6038 data] R1 = , wr2 = R indices (all data, 0.77Å) R1 = , wr2 = Largest diff. peak and hole and e.å nature chemistry

11 supplementary information Table S4 Crystal data and structure refinement for 4 3toluene, {[(Me 3 Si) 2 N] 2 Y} 4 ( 3 -ON=NO) 2 (THF) 2 3C 7 H 8. Empirical formula C 56 H 160 N 12 O 6 Si 16 Y 4 3C 7 H 8 Formula weight Temperature 153(2) K Wavelength Å Crystal system triclinic Space group P1 Unit cell dimensions a = (11) Å = (12). b = (11) Å = (12). c = (18) Å = (11). Volume (4) Å 3 Z 1 Density (calculated) Mg/m 3 Absorption coefficient mm -1 F(000) 1158 Crystal color colorless Crystal size 0.25 x 0.20 x 0.15 mm 3 Theta range for data collection 1.70 to Index ranges -15 h 15, -16 k 16, -26 l 26 Reflections collected Independent reflections [R(int) = ] Completeness to theta = % Absorption correction Semi-empirical from equivalents Max. and min. transmission and Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters / 0 / 541 Goodness-of-fit on F Final R indices [I>2.0σ(I) = data] R1 = , wr2 = R indices (all data, 0.77Å) R1 = , wr2 = Largest diff. peak and hole and e.å-3 nature chemistry 11