Addition of primary phosphines to the unsaturated triosmium cluster [(μ-H)Os3(CO)8{Ph2PCH2P(Ph)C6H4}]: Synthesis of triosmium clusters bearing dppm, phosphide and phosphinidene ligands via P–H bond activation

Treatment of the electronically unsaturated cluster [(μ-H)Os3(CO)8{Ph2PCH2P(Ph)C6H4}] (1) with primary phosphines PPhH2 and PCyH2 gives the phosphido bridged compounds [(μ-H)Os3(CO)8(μ-PPhH)(μ-dppm)] (2) and [(μ-H)Os3(CO)8(μ-PCyH)(μ-dppm)] (3), respectively, by P–H bond activation of the phosphines and demetallation of the phenyl ring of the diphosphine ligand. Thermolysis of 2 and 3 in refluxing octane at 128 °C results in the formation of the phosphinidene compounds [(μ-H)2Os3(CO)7(μ3-PPh)(μ-dppm)] (4) and [(μ-H)2Os3(CO)7(μ3-PCy)(μ-dppm)] (5), respectively, by further P–H bond cleavage of the phosphido groups. All the compounds have been characterized by infrared, 1H NMR, 31P{1H} NMR and mass spectroscopic data together with single-crystal X-ray diffraction studies for 4. Compound 4 consists of a triangular cluster of osmium atoms with a symmetrically capped phosphinidene ligand and a bridging dppm ligand.