Metallacarboxylic acids

Abstract

Metallacarboxylic acids (metal hydroxycarbonyls) are important intermediates in various transition metal-mediated reactions of CO and water, including the oxidation of CO by metal ions in aqueous solution, the homogeneously catalysed water-gas shift reaction and the formation of metal hydrides. The chemistry of the limited number of isolated metalla-carboxylic acids is surveyed and the first structural determination on such a compound, trans-Pt(CO2H)(C6H5)(PEt3)2, is mentioned. Metallacarboxylic acids are amphoteric, but this behaviour is strongly dependent on the central metal atom and on the nature of the other ligands present. Although β-elimination to give a metal hydride and CO2 is the usual mode of decomposition, this behaviour too is strongly metal- and ligand-dependent, and in the case of trans-Pt(CO2H)(C6H5)(PEt3)2 an alternative route has been identified, in which CO and H2O are lost and a dinuclear complex containing bridging CO2 is formed. Show more