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Gold(III)-CO and gold(III)-CO2 complexes and their role in the water-gas shift reaction

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Science Advances  16 Oct 2015:
Vol. 1, no. 9, e1500761
DOI: 10.1126/sciadv.1500761
  • Fig. 1 Principles of the carboxylate mechanism, based on the classical work on iron and ruthenium carbonyls (11, 12).
  • Fig. 2 Synthetic routes to Au(III)-CO complexes.

    Left inset shows the diagnostic aromatic region of the 1H NMR spectra of (C^N^C)AuOAcF (bottom), intermediate [(C^N^C)Au]+ [(C6F5)3BOAcF] (1) (middle), and product [(C^N^C)Au-CO]+ [(C6F5)3BOAcF] (2a) (top) (300 MHz, CD2Cl2, −30°C), confirming quantitative generation of the CO complex. Right inset shows the CO stretching bands of 2a and of 2a-13C in CH2Cl2 solution at −20°C, accompanied by the corresponding bands for 12CO2 and 13CO2, respectively, resulting from the reaction of the Au(III)-CO complex with traces of moisture.

  • Fig. 3 Molecular orbitals involved in Au-CO bonding, showing, from left to right, HOMO-1, HOMO, and LUMO in [(C^N^C)Au(CO)]+ as simulated by DFT.

    None of the lower-lying occupied orbitals shows any π-bonding interactions along the Au–CO vector.

  • Fig. 4 Gold(III)-mediated WGS reactions showing reaction steps A to C, the formation of the Au(III)-CO2 complex 3 via pathway D, and the reductive elimination of CO2 from 3 (step E).

    The colors indicate the H atoms that are diagnostic for monitoring these processes by 1H NMR spectroscopy, with associated chemical shifts. In the molecular structure of [(C^N^C)Au]2(μ-κCO-CO2)·∙C6H6 (3·∙C6H6), thermal ellipsoids are set at 50% probability level and hydrogen atoms and the solvent were omitted for clarity. The CO2 group is 50% disordered between two positions; the box shows the central core of the other position. Selected bond distances (in angstoms) and angles (in degrees) are as follows: Au(1)-C(26) 2.11(1); C(26)-O(1a) 1.18(1); C(26)-O(2′) 1.29(2); O(2′)-Au(1′) 2.036(9); Au(1)-N(1) 1.999(6); Au(1)-C(1) 2.064(8); Au(1)-C(17) 2.068(8); N(1)-Au(1)-C(26) 169.5(5); Au(1)-C(26)-O(1a) 129(1); Au(1)-C(26)-O(2′) 104(1); O(1a)-C(26)-O(2) 126(1); Au(1′)-O(2′)-C(26) 114(1); N(1′)-Au(1′)-O(2′) 160.5(3).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/9/e1500761/DC1

    Text

    Fig. S1. 1H NMR (CD2Cl2, −25°C) spectrum of 1.

    Fig. S2. Superposition of the IR spectra of [(C^N^C)Au12CO][B(C6F5)3OAcF] 2a and [(C^N^C)Au13CO][B(C6F5)3OAcF] 2a-13C.

    Fig. S3. 1H NMR spectrum of 2a (CD2Cl2, −20°C).

    Fig. S4. Stacked plot of the aromatic region of the 1H NMR spectra (CD2Cl2, −20°C) of (C^N^C)AuOAcF, [(C^N^C)Au(CH2Cl2)]+ 1, and [(C^N^C)Au(CO)]+ 2a.

    Fig. S5. 13C NMR (CD2Cl2, −20°C) spectrum of 2a13.

    Fig. S6. Monitoring by 1H NMR (CD2Cl2, −20°C) of the conversion of [(C^N^C)Au(η2-C2H4)]+ to [(C^N^C)Au(13CO)]+ (2a).

    Fig. S7. 1H NMR spectrum of 3 (CD2Cl2, 25°C). The inset shows the t-butyl resonances.

    Fig. S8. 13C NMR spectrum of complex 3-13C (CD2Cl2, 25°C).

    Fig. S9. Monitoring by 1H and 13C NMR spectroscopy of the thermolysis of complex 3-13C in CD2Cl2.

    Fig. S10. 1H NMR spectra of a solution of (C^N^C)AuOH in CD2Cl2 under 2 bar of CO at room temperature at different reaction times.

    Fig. S11. Aromatic and hydride regions of the 1H NMR spectra of a solution of (C^N^C)AuOH in CD2Cl2 and after CO addition for 30 s.

    Fig. S12. 1H NMR spectra in CD2Cl2 at room temperature of the aromatic region of [(C^N^C)Au]2O before and after its exposure to 2 bar of CO in the solid state.

    Fig. S13. Superposition of the IR spectra of [(C^N^C)Au]2O in the solid state and after exposure to 2 bar of CO for 8 hours.

    Fig. S14. 1H NMR spectrum of 4 (CD2Cl2, 25°C).

    Fig. S15. Superposition of the IR spectra of (C^N^C)AuCO2Me 4 (red) and (C^N^C)AuOMe (blue) in the solid state.

    Fig. S16. 1H NMR monitoring of the conversion of (C^N^C)AuOMe into (C^N^C)AuCO2Me 4 under 2 bar of 12CO at 25°C.

    Fig. S17. Reactivity of (C^N^C)AuOMe and 13CO in the presence of moisture.

    Fig. S18. Reaction of (C^N^C)AuOMe with CO.

    Fig. S19. HOMO-1, HOMO-2, and HOMO-3 for [(C^N^C)Au(CO)]+.

    Fig. S20. Enthalpy and Gibbs free energy values for reaction steps as calculated by DFT (T = 298.15 K).

    Table S1. Selected crystal data and structure refinement details for 3·C6H6.

    Table S2. CDA and d/b ratios of 2, [(C^N^N)Pt(CO)]+, and Pt(CO)2Cl2.

    DFT coordinates

  • Supplementary Materials

    This PDF file includes:

    • Text
    • Fig. S1. 1H NMR (CD2Cl2, −25°C) spectrum of 1.
    • Fig. S2. Superposition of the IR spectra of (C^N^C)Au12COB(C6F5)3OAcF 2a and (C^N^C)Au13COB(C6F5)3OAcF 2a-13C.
    • Fig. S3. 1H NMR spectrum of 2a (CD2Cl2, −20°C).
    • Fig. S4. Stacked plot of the aromatic region of the 1H NMR spectra (CD2Cl2, −20°C) of (C^N^C)AuOAcF, (C^N^C)Au(CH2Cl2)+ 1, and (C^N^C)Au(CO)+ 2a.
    • Fig. S5. 13C NMR (CD2Cl2, −20°C) spectrum of 2a13.
    • Fig. S6. Monitoring by 1H NMR (CD2Cl2, −20°C) of the conversion of (C^N^C)Au(η2-C2H4)+ to (C^N^C)Au(13CO)+ (2a).
    • Fig. S7. 1H NMR spectrum of 3 (CD2Cl2, 25°C). The inset shows the t-butyl resonances.
    • Fig. S8. 13C NMR spectrum of complex 3-13C (CD2Cl2, 25°C).
    • Fig. S9. Monitoring by 1H and 13C NMR spectroscopy of the thermolysis of complex 3-13C in CD2Cl2.
    • Fig. S10. 1H NMR spectra of a solution of (C^N^C)AuOH in CD2Cl2 under 2 bar of CO at room temperature at different reaction times.
    • Fig. S11. Aromatic and hydride regions of the 1H NMR spectra of a solution of (C^N^C)AuOH in CD2Cl2 and after CO addition for 30 s.
    • Fig. S12. 1H NMR spectra in CD2Cl2 at room temperature of the aromatic region of (C^N^C)Au2O before and after its exposure to 2 bar of CO in the solid state.
    • Fig. S13. Superposition of the IR spectra of (C^N^C)Au2O in the solid state and after exposure to 2 bar of CO for 8 hours.
    • Fig. S14. 1H NMR spectrum of 4 (CD2Cl2, 25°C).
    • Fig. S15. Superposition of the IR spectra of (C^N^C)AuCO2Me 4 (red) and (C^N^C)AuOMe (blue) in the solid state.
    • Fig. S16. 1H NMR monitoring of the conversion of (C^N^C)AuOMe into (C^N^C)AuCO2Me 4 under 2 bar of 12CO at 25°C.
    • Fig. S17. Reactivity of (C^N^C)AuOMe and 13CO in the presence of moisture.
    • Fig. S18. Reaction of (C^N^C)AuOMe with (CO).
    • Fig. S19. HOMO-1, HOMO-2, and HOMO-3 for (C^N^C)Au(CO)+.
    • Fig. S20. Enthalpy and Gibbs free energy values for reaction steps as calculated by DFT (T = 298.15 K).
    • Table S1. Selected crystal data and structure refinement details for 3·C6H6.
    • Table S2. CDA and d/b ratios of 2, (C^N^N)Pt(CO)+, and Pt(CO)2Cl2.
    • DFT coordinates

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