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(CO)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.