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.