Insertion of bis-ferrocenylbutadiyne into an osmium hydride bond. The synthesis, structure and electrochemical response of Os4(CO)11(μ-η-Z-FcCC(H)C2Fc)(μ-H)3

The reaction of Os4(CO)12(μ-H)4 with Me3NO followed by 1,4-bis(ferrocenyl)butadiyne (1) has yielded the tetraosmium product Os4(CO)11(μ-η2-FcCC(H)C2Fc)(μ-H)3 (5), Fc=C5H5FeC5H4 in 9% yield by decarbonylation and insertion of the 1,4-bis(ferrocenyl)butadiyne into one of the metal–hydrogen bonds in the cluster. Compound 5 was characterized by IR, 1H-NMR spectroscopy and single crystal X-ray diffraction analysis. The molecule contains a closed tetrahedral cluster of four osmium atoms with three bridging hydride ligands. One of the C–C triple bonds of 1 was inserted into one of the Os–H bonds to form a (bis-ferrocenyl)yneenyl ligand that bridges one edge of the cluster in a θ-π coordination mode. Compound 5 exhibits two one-electron oxidations for the ferrocenyl groups at E°=+0.443 and +0.486 V versus Ag/AgCl, ΔE°=0.043 V. This small difference indicates that there is little or no electronic communication between the two ferrocenyl groups.