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 thein 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 a nucleophile initiates a CO₂extrusion 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) hydridesviathe WGS reaction. In the case of methanol acting as a nucleophile attacking the gold(iii) carbonyl, no extrusion of CO₂is observed. Instead an intermediary gold(iii) carboxyl complex forms an aryl carboxylateviareductive 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.