Ionization of gold (γ-methoxy)vinyl complexes generates reactive gold vinyl carbene complexes.

Cationic gold vinyl carbene/allylic cation complexes of the form ()-[(L)AuC(H)C(H)CAr] OTf {L = IPr, Ar = Ph [()-], L = IPr, Ar = 4-CHOMe [()-], L = P(-Bu) -biphenyl, Ar = 4-CHOMe [()-]} were generated in solution Lewis acid-mediated ionization of the corresponding gold (γ-methoxy)vinyl complexes ()-(L)AuC(H)C(H)C(OMe)Ar at or below -95 °C. Complexes ()- and ()- were fully characterized in solution employing multinuclear NMR spectroscopy, which established the predominant contribution of the aurated allylic cation resonance structure and the significant distribution of positive charge into the γ-anisyl rings. Complex ()- reacted rapidly at -95 °C with neutral two-electron, hydride, and oxygen atom donors exclusively at the C1 position of the vinyl carbene moiety and with -methoxystyrene to form the corresponding vinylcyclopropane. In the absence of nucleophile ()- decomposed predominantly intermolecular carbene dimerization whereas formation of 1-aryl-5-methoxy indene upon ionization of ()-(IPr)AuC(H)C(H)C(OMe)(4-CHOMe) [()-] implicated an intramolecular Friedel-Crafts or electrocyclic Nazarov pathway for the decomposition of the unobserved vinyl carbene complex ()-[(IPr)AuC(H)C(H)C(4-CHOMe)] OTf [()-].