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*.