Since the recognition of metal-hydroxycarbonyl (or, metallacarboxylic acid) as a key intermediate in water gas shift (WGS) catalysis, numerous metal complexes incorporating hydroxycarbonyl ligands have been synthesized. In this Perspective, a brief account on the chemistry of metallacarboxylic acid and metallacarboxylate is presented. Special emphasis is placed on the hydroxycarbonyl-bridged dinuclear compounds. The relevance of hydroxycarbonyl complexes in the base-assisted reduction of ruthenium carbonyls is investigated. In particular, Lavigne's synthesis of Roper's catalyst Ru(CO) 2(PPh3)3, triruthenium dodecacarbonyl Ru 3(CO)12, and Bera's mechanistic investigation on the preparation of the metal-metal singly bonded diruthenim(i) complex [Ru 2(CO)4(CH3CN)6]2+ are described in detail. These reactions involve the decarboxylation of a "[Rum(COOH)n]" species, followed by the reductive elimination of HX (X = H, Cl or OH), steps akin to WGS catalysis. The prospect of hydroxycarbonyl chemistry in the development of bimetallic catalysis is examined. © 2010 The Royal Society of Chemistry.