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 [Os3(CO)11(NCMe)] at ambient temperature affords
substituted clusters:  the monosubstituted trinuclear cluster [Os3(CO)11{(PPh)4CH2}] (1) and the isomeric linked
bis-trinuclear clusters [{Os3(CO)11}2{μ-1,4-η2-(PPh)4CH2}] (2) and [{Os3(CO)11}2{μ-1,3-η2-(PPh)4CH2}] (3). Clusters
2 and 3 can also be prepared by further reaction of 1 with [Os3(CO)11(NCMe)]. The reaction at 100 °C gives, apart
from cluster 2, the disubstituted 1,4-bridged trinuclear cluster [Os3(CO)10{μ-1,4-η2-(PPh)4CH2}] (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
[Os3(CO)10(μ-H)2] at 100 °C in toluene, the 1,2,4-linked bis-trinuclear cluster [Os3(CO)11{μ3-1,2,4-η3-(PPh)4CH2}Os3(CO)8(μ-H)2] (5) is obtained. When I reacts with a 2-fold molar amount of [Os3(CO)10(μ-H)2], the 1,2,3,4-linked
bis-trinuclear hydride cluster [{Os3(CO)8(μ-H)2}2{μ4-1,2,3,4-η4-(PPh)4CH2}] (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.