Gas-phase synthesis and reactivity of a gold carbene complex.

Electrospray ionization tandem mass spectrometry of a phosphonium ylid complex of gold produces an ion whose mass and gas-phase chemical reactivity indicate that it is a gold benzylidene complex. The complex, with a supporting NHC ligand, corresponds to a type of reactive intermediates which have been presumed to act in gold-catalyzed cyclopropanation reactions, but which have not been observed to date in solution or gas-phase experiments. A threshold CID experiment also yields thermochemical information on the formation of the gold carbene from the ylid complex precursor.