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

Rosca, Dragos-Adrian, Fernandez Cestau, Julio, Morris, James, Wright, Joseph and Bochmann, Manfred (2015) Gold(III)-CO and gold(III)-CO2 complexes and their role in the water-gas shift reaction. Science Advances, 1 (9). ISSN 2375-2548

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    Abstract

    The water-gas shift (WGS) reaction is an important process for the generation of hydrogen. Heterogeneous gold catalysts exhibit good WGS activity, but the nature of the active site, the oxidation state, and competing reaction mechanisms are very much matters of debate. Homogeneous gold WGS systems that could shed light on the mechanism are conspicuous by their absence: gold(I)–CO is inactive and gold(III)–CO complexes were unknown. We report the synthesis of the first example of an isolable CO complex of Au(III). Its reactivity demonstrates fundamental differences between the CO adducts of the neighboring d8 ions Pt(II) and Au(III): whereas Pt(II)-CO is stable to moisture, Au(III)–CO compounds are extremely susceptible to nucleophilic attack and show WGS reactivity at low temperature. The key to understanding these dramatic differences is the donation/back-donation ratio of the M–CO bond: gold-CO shows substantially less back-bonding than Pt-CO, irrespective of closely similar n(CO) frequencies. Key WGS intermediates include the gold-CO2 complex [(C^N^C)Au]2(m-CO2), which reductively eliminates CO2. The species identified here are in accord with Au(III) as active species and a carboxylate WGS mechanism.

    Item Type: Article
    Additional Information: 2015 © The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC)
    Faculty \ School: Faculty of Science > School of Chemistry
    Depositing User: Pure Connector
    Date Deposited: 22 Oct 2015 15:03
    Last Modified: 27 Nov 2018 01:03
    URI: https://ueaeprints.uea.ac.uk/id/eprint/54783
    DOI: 10.1126/sciadv.1500761

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