Cluster Build-up Reactions using Di-gold Cationic Fragments: Synthesis and Structural Characterization of [Os7(CO)19(Au2dppm)]

The reaction of the di-gold cation Au₂(dppx)]²⁺ with the heptanuclear cluster dianion Os₇(CO)₂₀]^2– affords the mixed metal cluster Os₇(CO)₂₀{Au₂(dppx)}] (x=m (1), e (2), b (3)). On standing, in solution, this complex undergoes decarbonylation to give the cluster Os₇(CO)₁₉{Au₂(dppx)}] (x=m (4), e (5), b (6)). The complexes have been characterised spectroscopically, and an X-ray structure determination of the dppm derivative shows that it contains a metal core based on an Os₇ edge-bridged bicapped tetrahedron with the two ₃-Au atoms capping adjacent triangular Os₃ faces of the central tetrahedron. In an analogous reaction, the carbido anion Os₇(H)C(CO)₁₉]^– affords the neutral cluster Os₇C(CO)₁₉{Au₂(dppm)}] (7) when treated with Au₂(dppm)]²⁺ in the presence of base.