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 [Mo_2(η~5-C_5H _5)_2(μ-COMe)(μ-PCy_2)(μ-CO)] with several p -block elements (E) and their hydride derivatives

摘要

The unsaturated complex [Mo_2Cp_2(μ-COMe)(μ- PCy_2)(μ-CO)] (1) reacts with several HER_n molecules (HER_n = HSPh, HPHPh, HSnPh_3) in toluene at 263-288 K to give the corresponding derivatives [Mo_2Cp_2(μ-ER _n)(μ-PCy_2)(CO)_2]. A related reaction takes place in toluene at 263 K with the diphosphite (EtO)_2POP(OEt) _2 to give a mixture of the diethoxyphosphide derivatives [Mo _2Cp_2(μ-PCy_2){μ-P(OEt)_2}(CO) _2] and [Mo_2Cp(η~5-C_5H _4CH_2Ph)(μ-PCy_2){μ-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 [Mo_2Cp_2(μ-I)(μ-PCy _2)(CO)_2] and then the triiodide derivative [Mo _2Cp_2(μ-I)I_2(μ-PCy_2)(CO) _2]. In all of the above reactions, neat demethylation of the methoxycarbyne ligand takes place. In contrast, the silanes HSiPh_3 and H_2SiPh_2 (unreactive toward 1 in refluxing toluene) react slowly under visible-UV irradiation at room temperature to give in good yields the novel complexes [Mo_2Cp_2{μ-C(2-C _6H_4SiPh_2OMe)}(μ-PCy_2)(μ-CO)] and [Mo_2Cp_2(μ-CSiPh_2OMe)(μ-PCy _2)(μ-CO)], having arylcarbyne and silylcarbyne ligands, respectively, the latter resulting from the overall elimination of H_2 and insertion of Ph_2SiC_6H_4 and SiPh _2 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 [Mo _2Cp_2{μ-C(OMe)C(O)Se}(μ-PCy_2)(μ-Se _2)] and the O-methyldithiocarbonate [Mo_2Cp _2(μ-PCy_2){μ-S_2C(OMe)}(S)_2], the latter derived from an unexpected coupling of two sulfur atoms to the carbyne ligand.