Abstraction of methyl from neutral Fischer-type carbene complexes: A new site for nucleophilic attack

Reactions of Fischer-type carbene complexes, M(CO)(5)(C(OMe)Ph) (M = Cr, W), with metal carbonyl anions (M'(-) = CpFe(CO)(2)(-), Re(CO)(5)(-), Mn(CO)(4)PPh(3)(-) Co(CO)(3)PPh(3)(-), Cp*Cr(CO)(3)(-), CpMo(CO)(3)(-)) result in demethylation of the carbene complexes. The products are M(CO)(5)C(O)Ph(-) and M'-Me, characterized by infrared and MMR spectroscopy. A slower rate for reaction with W(CO)(5)(C(OEt)Ph) in comparison to the methyl analogue is consistent with nucleophilic attack of the metal carbonyl anion on the methyl of the methoxy group of the carbene. This is a new type of nucleophilic attack on a Fischer-type carbene.