Ligand-assisted heterolytic activation of hydrogen and silanes mediated bynitrosyl rhenium complexes

Abstr. of the hydride in the dinitrosyl rhenium complexes [Re(H)(NO)(2)(PR3 )(2)] (R = Pr-i (1a), Cy (1b)) affords the dinuclear saturated compounds [R e-2(H)(u,eta (2)-NO)(NO)(3)(PR3)(4)]-[BAr4'] (R = Pr-i, 2a; Cy, 2b) or the mononuclear unsaturated 16-electron derivatives [Re(NO)(2)(PR3)(2)] [BAr4'] (R = Pr-i, 3a; Cy, 3b). In complexes 2a,b the metal centers are connected via a nitrosyl-isonitrosyl linkage. Complexes 2 and 3 react with classical two-electron donor ligands such as CH3CN, CO, C6H5CHO, and THF, but also wi th H-2 and HSiEt3, In the two latter cases heterolytic rupture of the hydro gen-hydrogen or hydrogen -silicon bonds is achieved. Complexes 2a,b and 3a, b are active in the catalytic scrambling of H-2/D-2 to give HD under very m ild conditions. In the presence of tetramethylpiperidine as a base the reac tion of these complexes with H-2 produces [Re(H)(NO){NOH2NC5H6(CH3)(4)}(PR3 )(2)] [BAr4'] (R = Pr-i, 9a; Cy, 9b). Heterolysis of HSiEt3 mediated by 2a, b and 3a,b results in the formation of [Re(H)(NO)(NOSiEt3)(PR3)(2)] [BAr4'] (R = Pr-i, 8a; Cy, 8b). Complexes 8a and 9b have been characterized by X-r ay diffraction studies.