ALKYLATION AND SUBSTITUTION-REACTIONS OF METAL-CARBONYL ACYLATE AND CARBENE COMPLEXES
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Alkylation reactions of transs-LFe(CO)3C(O)R-Li+, where L = CO, PPh3, P(n-Bu)3, P(OMc)3, and P(OPh)3 and R = Ph, Me, and benzyl, employing as alkylating agents MeI, MeOSO2F, THFMe+SO3F3, and Et3O+BF4-, have been investigated. Alkoxonium salts react exclusively at the acyl oxygen yielding carbene complexes; ketones and products of [LFe(CO)3] are obtained from reaction of the acylate with Mel and MeOSO2F. The rate of Mel reaction with LFe(CO)3C(O)R-Li+ is ligand dependent with P(n-Bu)3 > PPh3 > P(OPh)3. Mel is found to react with metal carbonyl carbene complexes also to yield ketone, however too slowly to suggest intermediacy of carbene complex in the ketone synthesis directly from the acylate complex. Alkoxycarbene ligands as well as the acyl ligand (lithiooxycarbene) were found to labilize ligands trans to themselves, i.e., for X = Li or Et, the reaction is LFe(CO)3C(OX)R + L L + LFe- (CO)3C(OX)R. Mechanistic implications for the ketone synthesis based on the observation of ligand-exchange processes at both L and acyl sites (LFe(CO)3C(O)R-Li+ + L + LFe(CO)3L + [Li+C(O)R-]) are discussed. 1974, American Chemical Society. All rights reserved.