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 Os-4(CO)(12)(mu -H)(4) with Me3NO followed by 1 4-bis(ferrocenyl)butadiyne (1) has yielded the tetraosmium product Os-4(CO)(11)(mu-eta (2)-FcCC(H)C(2)Fc)(mu -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, H-1-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 theta-pi coordination mode. Compound 5 exhibits two one-electron oxidations for the ferrocenyl groups at E degrees = + 0.443 and + 0.486 V versus Ag/AgCl, DeltaE degrees = 0.043 V. This small difference indicates that there is little or no electronic communication between the two ferrocenyl groups. (C) 2001 Elsevier Science B.V. All rights reserved.