Trinuclear osmium clusters containing bidentate Ph2PCH2PPh2 and Me2PCH2PMe2 ligands: X-ray crystal structures of the complexes [Os3H(CO)9(Me2PCHPMe2)] and [Os3H(OH)(CO)8(Ph2PCH2PPh2)]

Abstract

The clusters [Os₃(CO)₁₀(dppm)](dppm = Ph₂PCH₂PPh₂) and [Os₃(CO)₁₀(dmpm)](dmpm = Me₂PCH₂PMe₂) react with trimethylamine N-oxide in acetonitrile solution to give [Os₃ CO)₉-(dppm)(MeCN)](1) and [Os₃(CO)₉(dmpm)(MeCN)](2) respectively. The acetonitrile ligand of (1) and (2) is readily displaced by other two-electron donor ligands to give [Os₃(CO)₉(dppm)L][L = PPh₃, P(OMe)₃, or Bu^tNC] and [Os₃(CO)₉(dmpm)L][L = P(OMe)₃ or C₂H₄]. Thermolysis of [Os₃(CO)₉(dmpm)(C₂H₄)] or [Os₃(CO)₁₀(dmpm)] gives the cyclometallated product [Os₃H (CO)₉-(Me₂PCHPMe₂)]. The acetonitrile complex (1) also reacts with HX (X = Cl or SR, R = alkyl) to give clusters of general formula [Os₃H(X)(CO)₈(dppm)], whereas for X = OH or OMe the only product isolated is [Os₃H(CO)₈{Ph₂PCH₂PPh(C₆H₄)}]. The dmpm derivative (2) reacts similarly with HCl and RSH. The cluster [Os₃H(OH)(CO)₈(dppm)], which can be prepared from [Os₂H-(OH)(CO)₁₀] and dppm, was found to have a different structure from [Os₃H(Cl)(CO)₈(dppm)]. All the products were characterised by i.r. and n.m.r. spectroscopy. The structures of [Os₃H(CO)₉-(Me₂PCHPMe₂)] and [Os₃H(OH)(CO)₈(dppm)] were confirmed by X-ray crystallography.