| The coordination chemistry of several Rh and Ir precursors, containing monodentate tertiary phosphines (PR3, R = aryl), in the presence of N-donor ligands (imines and amines), and aspects of the resulting mechanistic implications in their use as catalysts for the homogeneous H2-hydrogenation of imines, were investigated. The reactivity of the Rh(I) and Ir(I) precursors [M(diene)(PR3)2]PF6 (1) under 1 atm H2 was examined and several of the corresponding M(III)-bis(hydndo) complexes [M(H)2(PR3)2-(solv)2]PF 6 (2) formed in MeOH and acetone were isolated and characterized. While for M = Rh, complexes 2 exhibit moderate and low stability in the solid state and in solution, respectively, toward reductive elimination of H2, when M = Ir the corresponding species 2 display no tendency to lose H2 neither in the solid state nor in solution. Consequently, upon loss of H2 in solution ready formation of the corresponding cis-[M(PR3)2(solv) 2]PF6 (3), characterized in situ for solv = MeOH, acetone, was observed only when M = Rh.*; The new Rh(I) dimeric complexes [Rh2(PR3) 4][PF6]2 (R = Ph, 4a; p-tolyl, 4b), obtained by in vacuo removal of the coordinated solvent and hydrides from the corresponding 2, were isolated and characterized in both the solid state and in solution. The dimeric assembly observed in the solid state for complexes 4a and 4b is retained and as such observable only in CDCl3 and CD2Cl 2 solutions; however, evidence for a change in hapticity of the bridging arenes from η6 in the solid state to η4 in solution is presented. When R = benzyl (Bz), the 1:1 (Rh:phosphine) dimer Rh2(PBz3)2·PF5 ( 4c) was obtained. In coordinating media, species 4a and 4b generate 2 equivalents of the corresponding monomeric 3, and in either form provide useful precursors for an array of Rh(I) complexes.; Several of the aryl imines investigated undergo ortho-metallation at both Rh and Ir centers. Several new M(III)-o-metallated complexes [M(H){lcub}R′N=C(R″ )(o-C6H4){rcub}-(PR3) 2(solv)]PF6, with different combinations of R, R′ and R″, were isolated and/or characterized in situ for M = Ir and Rh (5–11). The Ir species display an inherent stability in all solvents, whereas some of the Rh analogues are fluxional in MeOH solution: solvent-exchange, discussed on the basis of variable temperature NMR studies, is proposed, and the implications of the kinetic lability of MeOH in catalytic hydrogenation reactions are discussed. (Abstract shortened by UMI.); *Please refer to dissertation for diagrams. |
