Tin-capped trinuclear nickel clusters: redox isomerism between micro(3)-stannyl and micro(3)-stannylene clusters of the class [Ni(3)(dppm)(3)(micro3-I)(micro3-SnCl(x)](n+) (x = 2, n = 1; x = 3, n = 0)

The reaction of Ni(3)(dppm)(3)(micro(3)-I)(2)) with sodium trichlorostannate affords the first tin-capped nickel cluster Ni(3)(dppm)(3)(micro(3)-I)(micro(3)-SnCl(3) (1). A site of coordinative unsaturation at tin can be introduced by the reaction of 1 with TlPF(6)] yielding the stannylene-capped cluster Ni(3)(dppm)(3)(micro(3)-I)(micro(3)-SnCl(2)](+) (2). Clusters 1 and 2 were characterized by 31P NMR, X-ray diffraction, and cyclic voltammetry (CV). Clusters 1 and 2 exhibit single electron redox chemistries, Ni(3)(dppm)(3)(micro(3)-I)(micro(3)-SnCl3](0/*-), Ni(3)(dppm)(3)(micro(3)-I)(micro(3)-SnCl(2)](+/0), that together comprise a redox equilibrium. Thus, electrochemical reduction of 1 produces first the 49e- cluster radical anion Ni(3)(dppm)(3)(micro(3)-I)(micro(3)-SnCl(3)](*-) which then yields the reduced form of 2, Ni(3)(dppm)(3)(micro(3)-I)(micro(3)-SnCl(2)], upon chloride dissociation.