Synthesis and characterisation of tetraosmium carbonyl clusters bearing anazo type ligand: crystal and molecular structures of [Os-4(mu-H)(4)(CO)(11)(NC5H4N=NPh)] and [Os-4(mu-H)(4)(CO)(10)(MeCN)(NC5H4N = NPh)]

Reaction of [Os-4(mu-H)(4)(CO)(10)(MeCN)(2)] with one equivalent of 4-phenp lazopyridine (4-PAP) in CH2Cl2 at ambient conditions afforded two new tetra osmium dusters [Os-4(mu-H)(4)(CO)(11) (NC5H4N=NPh)] (1) and [Os-4(mu-H)(4)( CO)(10)(MeCN)(NC5H4N=NPh)] (2) in moderate yields. Compound 1 exists as a p air of isomers in solution, which differ in the location of the bridging hy dride ligands. The molecular structures of clusters 1 and 2 consist of a hi ghly distorted tetrahedral metal skeleton, with the azo ligand terminally b onded to an osmium atom. (C) 1999 Elsevier Science S.A. All rights reserved .