Triosmium alkylidyne clusters containing monophosphine and chiral diphosphine ligands. Crystal and molecular structures of [Os₃(μ-H)₂(CO)₉(μ₃-CPBuⁿPh₂)] and (R)-[Os₃(μ-H)₂(CO)₈{μ₃-CPPh₂CH(Me)CH₂PPh₂}]

The cluster [Os3(μ-H)3(CO)9(μ3-CCl)] reacted with excess of butyldiphenylphosphine, in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu), to give the complex [Os3(μ-H)2(CO)9(μ3-CPBunPh2)] 1. The optically active diphosphine (R)-Ph2PCH(Me)CH2PPh2reacted similarly to give two isomers, (R)-[Os3(μ-H)2(CO)9{μ3-CPPh2CH(Me)CH2PPh2}] 2a and (R)-[Os3(μ-H)2(CO)9{μ3-CPPh2CH2CH(Me)PPh2}] 2b, which have been spectroscopically characterised. Complex 2a readily undergoes decarbonylation, followed by the formation of Os-P bond, to afford an octacarbonyl chiral cluster complex (R)-[Os3(μ-H2)(CO)8{μ3-CPPh2CH(Me)CH2PPh2}] 3. The molecular structures of 1 and 3 have been established by X-ray crystallography. Complex 1 contains a triosmium alkylidyne metal core with the BunPh2P moiety bonded to the apical carbon atom through the phosphorus atom. On the other hand, the structure of 3, which also contains a phosphine-substituted μ3-C ligand bonded to three osmium atoms at the base, is characterised by the formation of a six-membered osmacycle with the centre of chirality being retained in the phosphine ligand of the complex.