Bi- and poly-metallic cyanide-bridged complexes of the redox-active cyanomanganese nitrosyl unit [Mn(CN)(PR3)(NO)(η-C5H4Me)]

Abstract

Cationic nitrile complexes and neutral halide and cyanide complexes, with the general formula [MnL¹L²(NO)(η-C₅H₄Me)]^z, undergo one-electron oxidation at a Pt electrode in CH₂Cl₂. Linear plots of oxidation potential, E°′, vs.ν(NO) or the Lever parameters, E_L, for L¹ and L², allow E°′ to be estimated for unknown analogues.

In the presence of TlPF₆, [MnIL′(NO)(η-C₅H₄Me)] reacts with [Mn(CN)L(NO)(η-C₅H₄Me)] to give [(η⁵-C₅H₄Me)(ON)LMn(μ-CN)MnL′(NO)(η⁵-C₅H₄Me)][PF₆] which undergoes two reversible one-electron oxidations; ΔE, the difference between the potentials for the two processes, differs significantly for stable cyanide-bridged linkage isomers. Novel pentametallic complexes such as [Mn{(μ-NC)Mn(CNBu^t)(NO)(η⁵-C₅H₄Me)}₄(OEt₂)][PF₆]₂ and [Mn{(μ-NC)Mn(CNXyl)(NO)(η⁵-C₅H₄Me)}₄(NO₃-O,O′)][PF₆], containing a trigonal bipyramidal and a distorted octahedral Mn(II) centre, respectively, result either from slow decomposition of the binuclear cyanide-bridged species or from the reaction of anhydrous MnI₂ with four equivalents of [Mn(CN)L(NO)(η⁵-C₅H₄Me)] in the presence of TlPF₆.