Metallation of 2-ethenylpyridine at triosmium clusters: X-ray crystal structures of the open trinuclear clusters [Os3H(CO)9L(NC5H4CHCH)](L = CO or PMe2Ph)

Abstract

The compounds [Os₃H₂(CO)₁₀] and [Os₃(CO)₁₀(MeCN)₂] each react with 2-ethenylpyridine (NC₅H₄CHCH₂) with C–H bond cleavage at the terminal carbon atom to give [Os₃H(CO)₁₀-(NC₅H₄CHCH)], (1). An analogous compound [Os₃H(CO)₉(PMe₂Ph)(NC₅H₄CHCH)], (2), is formed similarly from [Os₃H₂(CO)₉(PMe₂Ph)]. Single-crystal X-ray structures of compounds (1) and (2) are reported. In these clusters the metal triangles have opened out with Os–Os–Os angles of 160.0(1) and 160.4(1)° in (1) and (2) respectively. Each of the compounds contains a terminal hydride ligand replaceable by Cl in carbon tetrachloride and has a five-electron donor NC₅H₄CHCH ligand chelating at a terminal Os atom of the Os₃ chain with a η²-alkene co-ordination at the central Os atom. 2-Ethynylpyridine (NC₅H₄CCH) reacts with [Os₃H₂(CO)₁₀] to give compound (1) and an isomer in which the alkene is trans rather than cis and in which the 2-pyridyl group is non-co-ordinated.