Synthesis and reactivity of the first stable chromium (VI) alkylidene complexes

The chromium(VI) dialkyl complex [Cr(NC6H3Pri2-2,6)2(CH2CMe3)2] readily eliminates CMe4 in room-temperature hydrocarbon and ether solutions to generate the hexavalent alkylidene species [Cr(NC6H3Pri2-2,6)2)(CMe3)] which can be trapped in the presence of strong donor molecules to give the first stable hexavalent chromium alkylidene complexes [Cr(NC6H3Pri2-2,6)2(CHCMe3(L)](L = thf, PMe3); in aromatic hydrocarbon solutions, the products obtained are those arising from C¿H activation across the chromium¿carbon double bond.