Synthesis, structure and reactivity of triosmium clusters derived from the reactions of [Os3(CO)10(μ-dppm)] (dppm = Ph2PCH2PPh2) and [Os3(μ-H)(Co)8{Ph2PCH2P(Ph)C6H4}] with PHPh2

The reaction of [Os-3(CO)(10)(mu-dppm)] 1 with diphenylphosphine in refluxing taluene led to the substituted cluster [Os-3(CO)(9)(mu-dppm)(PHPh2)] 3 and the phosphido-bridged dihydride [Os3H(mu-H)(CO)(7)(mu-dppm)(mu-PPh2)(2)] 4. The cluster 4 exists as three isomeric forms in solution. The 46-electron compound [Os-3(mu-H)(CO)(8){Ph2PCH2PCH2P(Ph)-C6H4}] 2 reacted with an excess of PHPh2 at room temperature to yield [Os-3(mu-H)(CO)(8){Ph2PCH2P(Ph)C6H4}-(PHPh2)] 5 and [Os-3(CO)(8)(mu-dppm)(PHPh2)(2)] 6 in 16 and 62% yields respectively. Thermolysis of 6 in refluxing toluene gave 4 and two stereoisomeric compounds 7 and 8 with stoichiometry [Os-3(mu-H)(2)(CO)(6)(mu-dppm) (mu-PPh2)(2)]. The cluster 3 decarbonylated at 110 degrees C to give the phosphido-bridged monohydride cluster [Os-3(mu-H)(CO)(8)-(mu-dppm)(mu-PPh2)] 9 which exists as two isomers in solution. Compound 4 converts into 7 and 8 on thermolysis in toluene. All the compounds have been characterized by infrared, H-1 and P-31-{H-1} NMR spectroscopy and elemental analysis and in the case of 3, 4, 6 and 7 also by X-ray crystallography.