Structure and Reactivity of Chromium(VI) Alkylidenes.

Bis(arylimido)Cr(VI) dialkyls lacking β-hydrogen decompose by α-hydrogen abstraction and, upon trapping with triphenylphosphine, yield isolable alkylidene complexes. Two such complexes, namely (ArN)2Cr═CHR(PPh3) (R = tBu, SiMe3), have been structurally characterized. The coordinatively unsaturated alkylidene intermediates are highly reactive; they effect C-H activation of saturated hydrocarbons and they react with olefins to produce metallacyclobutanes.