Reactions of tricarbonyl(η-hexamethylbenzene)chromium derivatives with nitrosonium and benzenediazonium ions: reversible oxidation versus nitrosyl- or areneazo-complex formation
Abstract
The complexes [Cr(CO)2L(η-C6Me6)][L = PPh3, PMePh2, PMe2Ph, P(OPh)3, or P(OMe)3] react with [NO][PF6] to afford [Cr(CO)L(η-C6Me6)(NO)][PF6], (I), and [Cr(CO)2(η-C6Me6)(NO)][PF6] whereas [PhN2][PF6] yields paramagnetic [Cr(CO)2L(η-C6Me6)][PF6](L = PPh3, PMePh2, or PMe2Ph) or [Cr(CO)L(η-C6Me6)(N2Ph)][PF6] and [Cr(CO)2(η-C6Me6)(N2Ph)][PF6][L = P(OMe)3 or P(OPh)3]. Electrochemical studies confirm that oxidation of [Cr(CO)2L(η-C6Me6)] to [Cr(CO)2L(η-C6Me6)]+ is a reversible one-electron process. The factors determining whether [NO]+ or [PhN2]+ oxidise organometallic complexes or cause substitution are discussed on the basis of the electrochemical and preparative results, and a general mechanism for the reactions of these ions with organotransition-metal complexes is proposed.