Structural Determination and Acidolysis Reactions of Ortho-Metalated Rhenium Tetrahydride Compounds Prepared from Reactions of ReH(7)(PPh(3))(2) with Benzylic Imines.

Reactions between ReH(7)(PPh(3))(2) and a series of benzylic imines, PhCHNR (R = Me, Ph, or Bn), produce the compounds ReH(4)eta(2)-(1,2-C(6)H(4))CHNR(2). One such compound, ReH(4)eta(2)-(1,2-C(6)H(4))CHNPh(2), was characterized by X-ray diffraction analysis. The compound ReH(4)eta(2)-(1,2-C(6)H(4))CHNPh(2) crystallizes in the P(&onemacr;) space group with the following unit cell dimensions: a = 12.422(3) Å, b = 12.696(3) Å, c = 13.604(5) Å, alpha = 93.26(2) degrees, beta = 90.66(2) degrees, gamma = 107.03(2) degrees, V = 2047.2 Å(3), and Z = 2. The structure was refined to R(F(o)) = 0.029 (R(w)(F(o)) = 0.034) for 5352 data with I > 3.0sigma(I). The structure determination indicates that ortho-metalation of the imine reactant occurs during the reaction of ReH(7)(PPh(3))(2) with PhCHNPh. The observation of four nu(Re-H) absorptions in the infrared spectrum of each ReH(4)eta(2)-(1,2-C(6)H(4))CHNR(2) compound indicates that the rhenium-bound hydrogen atoms, in these compounds, are better regarded as classical hydride ligands rather than as elongated dihydrogen ligands. Acidolysis reactions of the compounds ReH(4)eta(2)-(1,2-C(6)H(4))CHNR(2), with HBF(4).Et(2)O in acetonitrile, result in loss of the ortho-metalated imine ligands from the rhenium coordination spheres and in reduction of the imine functional groups to secondary ammonium cations. One hydride ligand is transferred to the imine carbon atom, during the course of each acidolysis reaction.