Addition of diphenyl diselenide (PhSeSePh) to the clusters [Os3(CO)10(μ-dppm)] and [(μH)Os3(CO)8{Ph2PCH2P(Ph)C6H4}]:: X-ray structures of [Os2(CO)4(μ-SePh)2(μ-dppm)], [Os3(CO)6(μ-CO)(μ-Se)2(μ-C6H4)(μ-dppm)] and two isomers of [Os3(CO)8(μ-SePh)2(μ-dppm)]

The reaction of [Os-3(CO)(10)(mu-dppm)] (4) with diphenyldiselenide in refluxing toluene at 110 degreesC affords the dinuclear compound [Os-2(CO)(4)(mu-SePh)(2)(mu-dppm)] (5), three 50 electron isomeric triosmium compounds 6, 7 and 8 with the formula [Os-3(CO)(8)(mu-SePh)(2)(mu-dppm)], two triosmium benzyne compounds [Os-3(CO)(6)(mu-CO)(mu-eta(2)-Se)(2)(mu-C6H4)(mu-dppm)] (9) and [Os-3(CO)(9)(mu-SePh)(2)(mu-eta(2)- C6H4)(mu-dppm)] (10) in 11%, 19%, 15%, 5%, 18% and 6% yields, respectively. Thermolysis of both 6 and 8 in refluxing toluene gives the dinuclear compound 5 in moderate yield, whereas a similar thermolysis of 7 yields 5 and 9 in 20% and 27% yields, respectively. Compound 10 converts to 9 refluxing in octane. Treatment of the unsaturated compound [(mu-H)Os-3(CO)(8) {Ph2PCH2P(Ph)C6H4}] (11) with diphenyldiselenide in refluxing benzene gives 5, 6, 7 and 8 in 8%, 20%, 25% and 10% yields, respectively. The molecular structures of 5, 6, 7 and 9 have been determined by single crystal X-ray diffraction studies. The molecular structure of 5 shows classical "sawhorse" structure with two bridging phenylselenido ligands as well as a dppm ligand. The solid-state structure of 6 reveals that two SePh groups span the open Os-Os edges of the Os-3 triangle, while the dppm ligand bridges one of the closed Os-Os edges. In compound 7, one SePh spans the open Os-Os site, while the other spans one of the two closed Os-Os edges and the dppm ligand bridges the third Os-Os vector. Compound 9, which exists as a mixture of two isomers in solution, contains two triply bridging selenido ligands and a benzyne ligand, which are believed to have been formed by the cleavage of Se-Se bond of the PhSeSePh ligand followed by C-Se and C-H activation of the SePh group. The 54 electron compound 10 has been characterized by elemental analysis, IR, H-1 NMR, P-31{H-1} NMR and mass spectroscopic data. (C) 2004 Elsevier B.V. All rights reserved.