Synthesis and characterization of hexaosmium carbonyl clusters containing pyridine ligands: Crystal and molecular structures of [Os6(CO)15(μ4-η2-CO)(C 5H5N)3], [Os6(CO)15(μ-H)(μ-CO)(μ3-O)-(C 5H5N)(μ-η2-NC5H4)]

Reaction of [Os6(CO)16(MeCN)2] with 1 equivalent of pyridine in CH2Cl2 at room temperature afforded three new clusters: [Os6(CO)15(μ4-η2-CO)(C 5H5N)3] 1, [Os6(CO)15(μ-H)(μ-CO)(μ3-O)(C 5H5N)(μ-η2-NC5H4)] 2 and [Os6(CO)14(μ-H)(μ-CO)(MeCN)(C5H 5N)(μ-η2-NC5H4)] 3 in 32, 10 and 25% yields respectively. Both clusters 2 and 3 contain an orthometallated pyridine ligand but with different metal core geometries. The molecular structure of cluster 2 revealed the presence of a novel μ3-O group bridging three osmium centres.