Formation of a Propeller-Shaped Ni4Ga3 Cluster Supported by Transmetalation of Cp* from Ga to Ni.

The reactivity of GaCp* toward different Ni0 olefin complexes is investigated. The reaction of GaCp* with [Ni(cdt)] (cdt = all-trans-1,5,9-cyclododecatriene) leads to simple adduct formation and the 18 valence electron (ve) compound [Ni(GaCp*)(cdt)] (1). In contrast, [Ni2(dvds)3] (dvds = 1,1,3,3-tetramethyl-1,3-divinyldisiloxane) is converted to the undercoordinated and highly reactive 16 ve complex [Ni(GaCp*)(dvds)] (2), which represents an intermediate in the formation of the propeller-shaped M7 cluster [Ni4Ga3](Cp*)3(dvds)2 (3). Extensive characterization of the latter compound by experimental and computational means reveals the Cp* transfer from Ga to Ni. Therefore, the title compound can be best expressed by the structural formula [(μ2-GaCp*)(Ni2)(μ2-GaNiCp*)2(dvds)2]. The flexible dvds ligands stabilize this arrangement via alkene-Ni and O-Ga interactions. Furthermore, compound 2 exhibits a fast GaCp* ligand exchange with external GaCp*, which is rather unexpected for the [TM(ECp*)a] compounds; they usually do not undergo substitution reactions with two electron donor ligands like CO, phosphines, or GaCp*.