d ( g-methoxy ) vinyl complexes generates reactive gold vinyl carbene complexes †

Cationic gold vinyl carbene/allylic cation complexes of the form (E)-[(L)AuC(H)C(H)CAr2] + OTf {L 1⁄4 IPr, Ar 1⁄4 Ph [(E)-5a], L 1⁄4 IPr, Ar 1⁄4 4-C6H4OMe [(E)-5b], L 1⁄4 P(t-Bu)2o-biphenyl, Ar 1⁄4 4-C6H4OMe [(E)-5c]} were generated in solution via Lewis acid-mediated ionization of the corresponding gold (g-methoxy)vinyl complexes (E)-(L)AuC(H)C(H)C(OMe)Ar2 at or below 95 C. Complexes (E)-5b and (E)-5c 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 g-anisyl rings. Complex (E)-5b 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 pmethoxystyrene to form the corresponding vinylcyclopropane. In the absence of nucleophile (E)-5a decomposed predominantly via intermolecular carbene dimerization whereas formation of 1-aryl-5methoxy indene upon ionization of (Z)-(IPr)AuC(H)C(H)C(OMe)(4-C6H4OMe)2 [(Z)-6b] implicated an intramolecular Friedel–Crafts or electrocyclic Nazarov pathway for the decomposition of the unobserved vinyl carbene complex (Z)-[(IPr)AuC(H)C(H)C(4-C6H4OMe)2] + OTf [(Z)-5b].