Chemistry of Unsaturated Group 6 Metal Complexes with Bridging Hydroxy and Methoxycarbyne Ligands. 6. C-E Bond Formation and C-O Bond Cleavage Processes in the Reactions of [Mo2(η5-C5H5)2(μ-COMe)(μ-PCy2)(μ-CO)] with Several p-Block Elements (E) and Their Hydride Derivatives

The unsaturated complex [Mo2Cp2(mu-COMe)(mu-PCy2)(mu-CO)] (1) reacts with several HER,, molecules (HERn = HSPh, HPHPh, HSnPh3) in toluene at 263-288 K to give the corresponding derivatives [Mo2Cp2(mu-ERn)(mu-PCy2)(CO)(2)]. A related reaction takes place in toluene at 263 K with the diphosphite (EtO)(2)POP(OEt)(2) to give a mixture of the diethoxyphosphide derivatives [Mo2Cp2(p-PCy2){mu-P(OEt)(2)}(CO)(2)] and [Mo2Cp(eta(5)-C5H4CH2Ph)(mu-PCy2){mu-P(OEt)(2)}(CO)(2)], the latter incorporating a benzyl group from the solvent, and with iodine (in dichloromethane at room temperature) to give first the iodide complex [Mo2Cp2(mu-I)(mu-PCy2)(CO)(2)] and then the triiodide derivative [Mo2Cp2(mu-I)I2Cu-PCy2)(CO)(2)]. In all of the above reactions, neat demethylation of the methoxyearbyne ligand takes place. In contrast, the silanes HSiPh3 and H2SiPh2 (unreactive toward 1 in refluxing toluene) react slowly under visible UV irradiation at room temperature to give in good yields the novel complexes [Mo2Cp2{mu-C(2-C6H4SiPh2OMe)}-(mu-PCy2)(mu-CO)] and [Mo2Cp2(mu-CSiPh2OMe)(mu-PCy2)(mu-CO)], having arylcarbyne and silylcarbyne ligands, respectively, the latter resulting from the overall elimination of H-2 and insertion of Ph2SiC6H4 and SiPh, fragments, respectively, into the strong C-OMe bond of the carbyne ligand. The reactions of 1 with elemental selenium and sulfur involve the incorporation of three to four chalcogen atoms to the dimetal center under mild conditions, to give respectively the carbene-seleniolate derivative [Mo2Cp2{mu-C(OMe)C(O)Sel(mu-PCy2)(mu-Se-2)] and the O-methyldithiocarbonate [Mo2Cp2(mu-PCy2)(mu-S,C(Ome)}(S),], the latter derived from an unexpected coupling of two sulfur atoms to the carbyne ligand.