Substitution reactions of a μ3-η1:η2:η1-C60 triosmium cluster complex and formation of a novel μ3-η1:η1:η2-C60 bonding mode

Decarbonylation of Os-3(CO)(8)(CNR)(mu(3)-CNR)(mu(3)-eta(1):eta(2):eta(1)-C-60) (1; R = CH2Ph) with Me3NO/ MeCN and subsequent thermal reactions with various 2e-donor ligands afford the respective substitution products Os-3(CO)(7)(CNR)(mu(3)-CNR)(L)(C-60) (L = (mu-H)(2) (2), CNR (3), PMe3 (4), PPh3 (5)) in high yields. Compounds 2-5 have been characterized by spectroscopic (MS, IR, and H-1, C-13, and P-31 NMR) and microanalytical data. Compounds 3 and 4 consist of three isomeric forms due to a 3-fold rotation on the outer Os center with a terminal benzyl isocyanide ligand, whereas 2 and 5 exist as a single isomer. The molecular structures of 2-5 have been determined by X-ray single-crystal diffraction studies. The hydride ligands of 2 have not been directly located, but ligand arrangements around the inner Os atom of the open-chain Os-3 framework, suggest that the two hydride ligands bridge the two Os-Os edges, respectively. The added isocyanide ligand in 3 is coordinated to an equatorial site on the inner Os center. The PPh3 ligand in 4 is positioned at the axial site of the inner Os atom. The mu(3)-eta(1):eta(2):eta(1)-C-60 interactions between C-60 and metal clusters are not significantly altered by substitution of the corresponding ligands in 2-4. The PPh3 ligand in 5, however, is bound at the less hindered equatorial site of the outer Os center and leads to an orbital, reorganization of the C-6 ring of C-60 from mu(3)-eta(1):eta(2):eta(1)-C-60 (1) to mu(3)-eta(1):eta(2):eta(1)-C-60 (5).