Experimental and theoretical studies on gold(iii) carbonyl complexes: reductive C,H- and C,C bond formation

Abstract

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 a 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 the 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.