Ligand-Assisted Heterolytic Activation of Hydrogen and Silanes Mediated by Nitrosyl Rhenium Complexes

Abstraction of the hydride in the dinitrosyl rhenium complexes [Re(H)(NO)2(PR3)2] (R =
iPr (1a), Cy (1b)) affords the dinuclear saturated compounds [Re2(H)(μ,η2-NO)(NO)3(PR3)4][BAr4‘] (R = iPr, 2a; Cy, 2b) or the mononuclear unsaturated 16-electron derivatives [Re(NO)2(PR3)2][BAr4‘] (R = iPr, 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 with H2 and HSiEt3. In the two
latter cases heterolytic rupture of the hydrogen−hydrogen or hydrogen−silicon bonds is
achieved. Complexes 2a,b and 3a,b are active in the catalytic scrambling of H2/D2 to give
HD under very mild conditions. In the presence of tetramethylpiperidine as a base the
reaction of these complexes with H2 produces [Re(H)(NO){NOH2NC5H6(CH3)4}(PR3)2][BAr4‘]
(R = iPr, 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 = iPr, 8a; Cy, 8b). Complexes 8a and
9b have been characterized by X-ray diffraction studies.