The clusters [M_a(ECp*)_b] (M = Pd, Pt; e = Al, Ga, In): Structures, fluxionality, and ligand exchange reactions

The synthesis and structural characterization of the novel homoleptic cluster complexes [Pd₂(GaCp*)₂(μ₂- GaCp*)₃] (1c), [Pd₃(GaCp*)₄(μ ₂-GaCp*)₄] (2b) and [Pd₃(AlCp*) ₂(μ₂-AlCp*)₂(μ₃-AlCp *)₂] (3) (Cp* = C₅Me₅) are presented. Furthermore, ligand exchange reactions of these cluster complexes are explored. In contrast to the electronically and sterically saturated complexes [M(ECp*)₄] (M = Ni, Pd, Pt), the new unsaturated analogues [M_a(ER)_b] (E = Al, Ga, In) react with a variety of typical ligands (Cp*Al, CO, phosphines, isonitriles) to give new di-and tri-substituted compounds like [Pt₂(GaCp*)₂(μ ₂-AlCp*)₃] (1d), [PdPt-(GaCp*)(PPh ₃)(μ₂,-GaCp*)₃] (4b), or [Pd ₃(PPh₃)₃(μ₂-InCp*) (μ₃-InCp*)₂] (8). The trends of the reactivity of [M_a(ER)_b] as well as their fluxional behavior in solution has been elucidated by NMR spectroscopy, resulting in a mechanistic rationale for the ligand exchange reactions as well as the fluxional processes.