1,2,3,4-Tetraphenyl-1,2,3,4-tetraphospholane,a highly versatile cyclocarbaphosphine ligand: reactions with activated triosmium clusters and characterization of the products

Reaction of 1,2,3,4-tetraphenyl-1,2,3,4-tetraphospholane (I) with Os(3)(CO)(11)(NCMe)] at ambient temperature affords substituted clusters: the monosubstituted trinuclear cluster Os(3)(CO)(11)(PPh)(4)CH(2)]] (1) and the isomeric linked bis-trinuclear clusters Os(3)(CO)(11)](2)mu-1,4-eta(2)-(PPh)(4)CH(2)]] (2) and Os(3)(CO)(11)](2)mu-1,3-eta(2)-(PPh)(4)CH(2)]] (3). Clusters 2 and 3 can also be prepared by further reaction of 1 with Os(3)(CO)(11)(NCMe)]. The reaction at 100 degrees C gives, apart from cluster 2, the disubstituted 1,4-bridged trinuclear cluster Os(3)(CO)(10)mu-1,4-eta(2)-(PPh)(4)CH(2)]] (4). The conversion of 1 into 4 can be achieved through the pyrolysis of a solution of 1. When 1 reacts with an equimolar amount of Os(3)(CO)(10)(mu-H)(2)] at 100 degrees C in toluene, the 1,2,4-linked bis-trinuclear cluster Os(3)(CO)(11)mu(3)-1,2,4-eta(3)-(PPh)(4)CH(2)]Os(3)(CO)(8)(mu-H)(2)] (5) is obtained. When I reacts with a 2-fold molar amount of Os(3)(CO)(10)(mu-H)(2)], the 1,2,3,4-linked bis-trinuclear hydride cluster Os(3)(CO)(8)(mu-H)(2)](2)mu(4)-1,2,3,4-eta(4)-(PPh)(4)CH(2)]] (6) is obtained. Cluster 1 exists as two conformational isomers (1y and 1r) in the crystalline state, due to different conformational arrangements of pseudoaxial carbonyls in the cluster. Cluster 3 shows two interconvertible conformers (3y and 3r) due to the inversion of the configuration of the uncoordinated outer phosphorus atom, and a pair of enantiomers exists in 3r. All of the new compounds obtained have been characterized by spectroscopic and analytical techniques, and their structures have been established by X-ray crystallography.