Reaction of pentafluoronitrosobenzene with [Os3(CO)11(CH3CN)] and high-performance liquid chromatographic separation of [Os3(CO)11(μ-ONC6F5)], [Os3(CO)9(μ3-NC6F5)2], [Os3(CO)11(CH3CN)] and Os3(CO)12

Abstract Reaction of pentafluoronitrosobenzene with [Os 3 (CO) 11 (CH 3 CN)] in THF at room temperature yields a new triosmium cluster, [Os 3 (CO) 11 (μ-ONC 6 F 5 )] ( I ), where the pentafluorophenylnitroso ligand has been shown by X-ray crystallography to adopt an unusual bonding mode, with its nitrogen bridging two non-bonded osmium atoms and the oxygen atom bonded to one of the osmium atoms. The separation of [Os 3 (CO) 11 (μ-ONC 6 F 5 )] (I), [Os 3 (CO) 9 (μ 3 -NC 6 F 5 ) 2 ] ( II ) and their parent triosmium clusters, i.e. [Os 3 (CO) 11 -(CH 3 CN)] and Os 3 (CO) 12 , by high-performance liquid chromatography is also described.