Gold Difluorocarbenoid Complexes: Spectroscopic and Chemical Profiling.

Gold carbenes of the general type [LAu=CR ] are sufficiently long-lived for spectroscopic inspection only if the substituents compensate for the largely missing stabilization of the carbene center by the [LAu] fragment. π-Donation by two fluorine substituents (R=F) is insufficient; rather, difluorocarbene complexes are so deprived in electron density that they sequester even "weakly coordinating" anions such as triflate or triflimide. This particular bonding situation translates into unmistakable carbenium ion chemistry upon reaction with stilbene as a model substrate.