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Treatment of the electronically unsaturated cluster [(μ-H)Os3(CO)8(Ph2PCH2P(Ph)C6H4)] (1) with HCl gas at ambient temperature in dichloromethane afforded (μ-H)Os3(CO)8(μ-Cl)(μ-dppm) (2) and [(μ-H)Os3(CO)7(η1-Cl)(μ-Cl)2(μ-dppm)] (3). Thermolysis of 2 at 110 °C led to an isomer of 2, 4. A similar reaction of 1 with HBr gas gave [(μ-H)Os3(CO)8(μ-Br)(μ-dppm)] (5) as the only product which does not isomerize at 110 °C. In sharp contrast, treatment of 1 with HF gas gave the protonated species [(μ-H)2Os3(CO)8(Ph2PCH2P(Ph)C6H4)]+ (6). Treatment of 1 with CF3CO2H also gave cation 6 whereas CH3CO2H yielded [(μ-H)Os3(CO)8(μ-η2-CH3CO2)(μ-dppm)] (7). Structures of 2, 3, 4 and 6 were established crystallographically. In 2, both the chloride and the hydride ligands simultaneously bridge the same Os–Os edge and the dppm spans another Os–Os bond whereas in 4, all the three ligands bridge the same Os–Os edge. Compound 3 is comprised of an open Os3 arrangement in which one chloride bridges the open Os⋯Os edge, another chloride and a hydride mutually bridge an Os–Os bond and the third chloride is terminally coordinated to one of the Os atoms of the dppm bridged edge. The cation 6 consists of a triangle of osmium atoms in which the shortest Os–Os edge is bridged by a hydride and the metallated phenyl ring and the longest edge is bridged by another hydride and the diphosphine ligand.

Treatment of [Os 3 (CO) 7 (μ 3 -S) 2 (μ-dppm)] ( 1 ) with Me 3 NO in toluene at 80 °C affords the trinuclear cluster [Os 3 (CO) 6 (μ 3 -S) 2 (NMe 3 )(μ-dppm)] ( 2 ) and the hexanuclear cluster [Os 6 (CO) 12 (μ 3 -S) 4 (μ-dppm) 2 ] ( 3 ) in 30% and 51% yields, respectively. The reaction of 1 with [Os 3 (CO) 10 (MeCN) 2 ] in refluxing benzene at 80 °C gives the hexanuclear cluster [Os 6 (CO) 14 (μ 3 -S) 2 (μ-dppm)] ( 4 ) in 15% yield. Compound 2 reacts with CO, PPh 3 and P(OMe) 3 at room temperature to give 1 , [Os 3 (CO) 6 (μ 3 -S) 2 (μ-dppm)(PPh 3 )] ( 5 ) and [Os 3 (CO) 6 (μ 3 -S) 2 (μ-dppm){P(OMe) 3 }] ( 6 ), respectively; in high yields indicating that the NMe 3 ligand is weakly bound. Compound 1 reacts with PPh 3 in presence of Me 3 NO to afford 5 , 2 and 3 in 53%, 6% and 18% yields, respectively, whereas with P(OMe) 3 1 gives only 6 in 84% yield. Compound 3 reacts with CO at 98 °C to regenerate 1 by the cleavage of the three unsupported osmium–osmium bonds. The molecular structures of 4 and 6 have been unambiguously determined by single crystal X-ray diffraction studies. The hexanuclear compound 3 appears to be a64-electron butterfly core with four triply bridging sulfido ligands and two bridging dppm ligands based on the spectroscopic and analytical data. The metal core of 4 can be described as a central tetrahedral array capped on two faces with two additional osmium atoms. The triply bridging sulfido ligands face cap the two tetrahedral arrays formed by metal capping of the two faces of the central tetrahedron. The dppm ligand bridges one edge of one of the external tetrahedral arrays. Compounds 5 and 6 are formed by the displacement of equatorial carbonyl group of 1 by a PPh 3 and P(OMe) 3 ligand respectively and their structures are comparable to that of 1 .

The unsaturated cluster [(μ-H)Os 3 (CO) 8 {Ph 2 PCH 2 P(Ph)C 6 H 4 }] ( 2 ) reacts with elemental selenium at 110 °C to give two triosmium clusters [Os 3 (CO) 7 (μ 3 -Se) 2 (μ-dppm)] ( 3 ), [Os 3 (CO) 7 (μ 3 -CO)(μ 3 -Se)(μ-dppm)] ( 4 ) and the tetraosmium cubane-like cage cluster [Os 4 (CO) 10 (μ 3 -Se) 4 (μ-dppm)] ( 5 ) in 20, 47 and 5% yields, respectively. Treatment of the labile cluster [Os 3 (CO) 10 (MeCN) 2 ] with dppmSe at ambient temperature gives the dinuclear compound [Os 2 (CO) 6 (μ-Se)(μ-dppm)] ( 6 ) along with 3 and 4 in 13, 24 and 4% yields, respectively, while with dppmSe 2 at 80 °C it yields 3 and 5 in 27 and 7% yields, respectively, by oxidative transfer of selenium atoms to the metal center. The reaction of 3 with Me 3 NO at 80 °C leads to loss of 1 mol of CO and formation of the condensation derivative [Os 6 (CO) 12 (μ 3 -Se) 4 (μ-dppm) 2 ] ( 7 ), containing a central 64-electron butterfly core, in 75% yield. Compound 7 reacts with CO at 98 °C to regenerate 4 by cleavage of the three unsupported metalmetal bonds. In the disubstituted square-pyramidal selenido cluster, 3 , the dppm ligand bridges two bonded osmium atoms whereas in 7 both the dppm ligands bridge the open osmium–osmium edges. Treatment of 3 with PPh 3 in the presence of Me 3 NO at room temperature gives the phosphine-substituted compound [Os 3 (CO) 6 (μ 3 -Se) 2 (μ-dppm)(PPh 3 )] ( 8 ) and the dimer 6 in 26 and 20% yields, respectively. The structure of 8 is comparable with that of 3 from which it is derived by replacing one equatorial carbonyl group with the PPh 3 ligand. The molecular structures of the complexes 3 , 4 , 6 , 7 and 8 have been fully elucidated by single-crystal X-ray diffraction studies.

Treatment of the electronically unsaturated cluster Os-3(CO)(8)(mu(3)-eta(2)-Ph2PCH2P(Ph)C6H4)(mu-H) (1) with benzothiophene in refluxing m-xylene afforded Os-3(CO)(7)(mu-PPh2)(mu-PMePh)(mu(3)-eta(2)-C6H4) (2), Os-3(CO)(7)(mu(3)-eta(2)-PPh(C6H4)CH2PPh)(mu(3)-eta(3)-SC8H5)(mu-H) (3), and Os-3(CO)(8)(mu-CO)(mu(3)-eta(2)-PPh(C6H4)CH2PPh) (4). Thermolysis of 1 in refluxing toluene for 35 h afforded only 4, whereas in refluxing m-xylene it gave both 4 and 2. Compound 4 can also be obtained from the thermolysis of Os-3(CO)(9)(mu(3)-eta(2)-PPh(C6H4)CH2PPh2)(mu-H) (5) in refluxing toluene. All the complexes have been structurally characterized. Compound 3 contains a unique example of a mu(3)-eta(2) benzothienyl ligand coordinated through the sulfur atom and the C-C double bond of the five-membered ring in a sigma,pi vinyl fashion. This coordination mode results in the rupture of one osmium-osmium bond, whereas the basic triangular metal framework is retained in the case of 2 and 4, which are derived from the activation of P-C and C-H bonds of 1 and do not contain any benzothiophene-derived ligand. (Less)