Reduction of CO2 by Pyridine Monoimine Molybdenum Carbonyl Complexes: Cooperative Metal–Ligand Binding of CO2

Authors

  • Dr. Daniel Sieh,

    1. Joint Center for Artificial Photosynthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (USA)
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    • These authors contributed equally to this work.

  • Dr. David C. Lacy,

    1. Joint Center for Artificial Photosynthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (USA)
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    • These authors contributed equally to this work.

  • Prof. Dr. Jonas C. Peters,

    1. Joint Center for Artificial Photosynthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (USA)
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  • Prof. Dr. Clifford P. Kubiak

    Corresponding author
    1. Joint Center for Artificial Photosynthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (USA)
    2. Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive MC 0358, La Jolla, California 92093 (USA)
    • Joint Center for Artificial Photosynthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (USA)

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Abstract

[(ArPMI)Mo(CO)4] complexes (PMI=pyridine monoimine; Ar=Ph, 2,6-di-iso-propylphenyl) were synthesized and their electrochemical properties were probed with cyclic voltammetry and infrared spectroelectrochemistry (IR-SEC). The complexes undergo a reduction at more positive potentials than the related [(bipyridine)Mo(CO)4] complex, which is ligand based according to IR-SEC and DFT data. To probe the reaction product in more detail, stoichiometric chemical reduction and subsequent treatment with CO2 resulted in the formation of a new product that is assigned as a ligand-bound carboxylate, [(math formulaPMI)Mo(CO)3(CO2)]2−, by NMR spectroscopic methods. The CO2 adduct [(math formulaPMI)Mo(CO)3(CO2)]2− could not be isolated and fully characterized. However, the C[BOND]C coupling between the CO2 molecule and the PDI ligand was confirmed by X-ray crystallographic characterization of one of the decomposition products of [(math formulaPMI)Mo(CO)3(CO2)]2−.

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