Structural and nuclear magnetic resonance studies of triosmium and triruthenium carbonyl cluster derivatives containing pentaphenylcyclopentaphosphane

Abstract

The reaction of pentaphenylcyclopentaphosphane (PPh)5 with [Os3(CO)10(NCMe)2] in 1:1 molar ratio afforded a pair of inversion isomers, 1 and 2, with the molecular formula [Os3(Cp)10{(PPh)5}]. A similar reaction in 3:1 molar ratio gave a different cluster [Os3(CO)10{(PPh)5}2] 3. The clusters [Os3(CO)11{(PPh)5}] 4 and [{Os3(CO)11}2{(PPh)5}] 5 were obtained from reaction of (PPh)5 with [Os3(CO)11(NCMe)]. Compound 4 reacted with [Ru3(CO)11(NCMe)] to generate the cluster [(OC)11Os3{(PPh)5}Ru3(CO) 11] 6. Compounds 4 and 5 were converted into 1 and 2 when heated in sealed tubes at 80°C. In clusters 1 and 2 the triosmium unit is chelated by the cyclophosphane ligand through the 1,3-phosphorus atoms of the ring, and their main difference lies in the orientations adopted by the aromatic rings attached to the unco-ordinated phosphorus. Variable-temperature NMR studies showed that the two inversion isomers can undergo interconversion. In 4 one osmium atom of the triosmium unit is co-ordinated to one phosphorus atom of the cyclophosphorus ligand, while in 5 the two triosmium units are each linked via co-ordination of one Os atom to a phosphorus atom of the cyclophosphane ring. With the help of two-dimensional 31P NMR spectroscopy, the correlations between phosphorus atoms for clusters 1, 2, 4 and 5 were established.