Synthesis, structure, and reactivity of a gold carbenoid complex that lacks heteroatom stabilization

Hydride abstraction from the neutral gold cycloheptatrienyl complex [(P)Au(η(1)-C7H7)] (P=P(tBu)2(o-biphenyl)) with triphenylcarbenium tetrafluoroborate at -80 °C led to the isolation of the cationic gold cycloheptatrienylidene complex [(P)Au(η(1)-C7H6)](+) BF4(-) in 52% yield, which was characterized in solution and by single-crystal X-ray diffraction. This cycloheptatrienylidene complex represents the first example of a gold carbenoid complex that lacks conjugated heteroatom stabilization of the electron-deficient C1 carbon atom. The cycloheptatrienylidene ligand of this complex is reactive; it can be reduced by mild hydride donors, and converted to tropone in the presence of pyridine N-oxide.