Experimental and Theoretical Studies on Gold(III) Carbonyl Complexes: Reductive C,H- and C,C Bond Formation

The reactivity of cationic (C^C)gold(III) carbonyl complexes was investigated. While the in situ-formed IPrAu(bph)CO+ complex (bph = biphenyl-2,2’-diyl) does not undergo a migratory insertion of CO into the neighboring gold-carbon bond, nucleophiles can attack the coordinated CO moiety intermolecularly. Water as nucleophile initiates a CO2 extrusion combined with a reductive C,H bond formation. The rapid formation of a gold(I) species from an intermediary gold(III) carbonyl has not been observed before and shows a significant difference in reactivity between (C^C) and (C^N^C)gold(III) carbonyls. The latter have been reported to form stable gold(III) hydrides via the WGS reaction. In case of methanol acting as a nucleophile attacking the gold(III) carbonyl, no extrusion of CO2 is observed. Instead an intermediary gold(III) carboxyl complex forms an aryl carboxylate via reductive C-C bond elimination. Experimental and theoretical studies on the mechanism explain the observed selectivities and give new insights into the reactivity of elusive gold(III) carbonyls.