Mixed metal cluster complexes containing the bis-ferrocenylbutadiyne ligand: their structures and electrochemical responses

Two new platinum-triosmium cluster complexes PtOs₃(CO)₉(COD)(μ₄-FcC₄Fc) (4) and Pt₂Os₃(CO)₁₀(COD)(μ₅-FcC₄Fc) (5) containing the electroactive 1,4-bis-ferrocenylbutadiyne ligand FcC₄Fc were obtained from the reaction of Os₃(CO)₁₀(μ₃-FcC₄Fc) (3) with Pt(COD)₂. Compounds 4 and 5 were characterized by IR and ¹H-NMR spectroscopy, by single crystal X-ray diffraction analysis and by differential pulse voltammetry. Compound 4 consists of a butterfly cluster of one platinum and three osmium atoms with the platinum atom in one of the wing-tip positions. The cluster is co-ordinated to one of the C---C triple bonds of the FcC₄Fc ligand in the μ₄-bonding mode. Cluster 5 exhibits the bow tie structure for five metal atoms: two of platinum and three of osmium. Both triple bonds of the butadiyne ligand are co-ordinated in this complex. Both products show two one electron oxidations for the ferrocenyl groups: for 4 at E°=+0.356 and +0.503 V versus Ag AgCl, and for 5 at E°=+0.478 and +0.576 V.