TRIOSMIUM ALKYLIDYNE CLUSTERS CONTAINING MONOPHOSPHINE AND CHIRAL DIPHOSPHINE LIGANDS - CRYSTAL AND MOLECULAR-STRUCTURES OF [OS-3(MU-H)(2)(CO)(9)(MU(3)-CPBU(N)PH(2))] AND (R)-[OS-3(MU-H)(2)(CO)(8)(MU(3)-CPPH(2)CH(ME)CH(2)PPH(2))]

The; cluster [Os-3(mu-H)(3)(CO)(9)(mu(3)-CCl)] reacted with excess of butyldiphenylphosphine, in the presence of 1,8-diazabicyclo [5.4.0]undec-7-ene (dbu), to give the complex [Os-3(mu-H)(2)(CO)(9)(mu(3)-(CPBuPh2)-Ph-n)] 1. The optically active diphosphine (R)-Ph2PCH(Me)CH2PPh2 reacted similarly to give two isomers, (R)-[Os-3{mu-H)(2)(CO)(9){mu(3)-CPPh2CH(Me)CH2PPh2}]: 2a and (R)-[Os-3(mu-H)(2)(CO)(9){mu(3)-CPPh2CH2CH-(Me)PPh2}] 2b, which have been spectroscopically characterised. Complex 2a readily undergoes decarbonylation, followed by the formation of Os-fa bond, to afford an octacarbonyl chiral cluster complex (R)-[Os-3(mu-H)(2)(CO)(8)(mu(3)-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 (BuPh2P)-Ph-n 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 mu(3)-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.