High-yield synthesis of osmium complexes [(η6-C6H6)OsCl2]2, [CpOs(η6-C6H6)]+ and CpOs(η5-cyclohexadienyl)

The benzene complex [(η6-C6H6)OsCl2]2 (1) was obtained in 97% yield from thermal or microwave-assisted reaction of Na2OsCl6 with 1,3-cyclohexadiene in aqueous ethanol. Further reaction of 1 with TlCp gives [CpOs(η6-C6H6)]PF6 in 75% yield. Treatment of [CpM(η6-C6H6)]PF6 (M = Ru and Os) with NaBH4 in wet THF affords the cyclohexadienyl complexes CpM(η5-C6H7) in almost quantitative yields. The structure of [CpOs(η6-C6H6)]BArF (BArF = [B((3,5-(CF3)2)C6H3)4]) was confirmed by X-ray diffraction.