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 (PR 3 ) 2 ] (R = i Pr ( 1a ), Cy ( 1b )) affords the dinuclear saturated compounds [Re 2 (H)(μ,η 2 -NO)(NO) 3 (PR 3 ) 4 ][BAr 4 ‘] (R = i Pr, 2a; Cy, 2b ) or the mononuclear unsaturated 16-electron derivatives [Re(NO) 2 (PR 3 ) 2 ][BAr 4 ‘] (R = i Pr, 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 CH 3 CN, CO, C 6 H 5 CHO, and THF, but also with H 2 and HSiEt 3 . 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 H 2 /D 2 to give HD under very mild conditions. In the presence of tetramethylpiperidine as a base the reaction of these complexes with H 2 produces [Re(H)(NO){NOH 2 NC 5 H 6 (CH 3 ) 4 }(PR 3 ) 2 ][BAr 4 ‘] (R = i Pr, 9a; Cy, 9b ). Heterolysis of HSiEt 3 mediated by 2a, b and 3a, b results in the formation of [Re(H)(NO)(NOSiEt 3 )(PR 3 ) 2 ][BAr 4 ‘] (R = i Pr, 8a; Cy, 8b ). Complexes 8a and 9b have been characterized by X-ray diffraction studies.