Synthesis, structure, and kinetic studies on [RuCl2(NCCH3)2(cod)]
Autores: Jesús J. Pérez-Torrente, Carmen Cunchillos, Daniel Gómez-Bautista, M. Victoria Jiménez, Ricardo Castarlenas, Fernando J. Lahoz y Luis Oro
Ref. revista: Journal of Coordination Chemistry, 65, 2981-2991 (2012)
[RuCl2(NCCH3)2(cod)], an alternative starting material to [RuCl2(cod)]n for the preparation of ruthenium(II) complexes, has been prepared from the polymer compound and isolated in yields up to 87% using a new work-up procedure. The compound has been obtained as a yellow solid without water of crystallization. The complexes [RuCl2(NCR)2(cod)] spontaneously transform into dimers [Ru2Cl(-Cl)3(cod)2(NCR)] (R¼Me, Ph). 1H NMR kinetic experiments for these
transformations evidenced first-order behavior. [RuCl2(NCPh)2(cod)] dimerizes slower by a factor of ten than [RuCl2(NCCH3)2(cod)]. The following activation parameters, DH#¼114 3 kJ mol1 and DS#¼669 JK1 mol1 for R¼CH3CN (DG#¼945 kJ mol1, 298.15 K) and DH#¼1222 kJ mol1 and DS#¼756JK1 mol1 for R¼Ph (DG#¼1004 kJ mol1,298.15 K), have been calculated from the first-order rate constants in the temperature range
294–323 K. The kinetic parameters are in agreement with a two-step mechanism with dissociation of acetonitrile as the rate-determining step. The molecular structures of [Ru2Cl(- Cl)3(cod)2(NCR)] (R¼Me, Ph) have been determined by X-ray diffraction.
[RuCl2(NCCH3)2(cod)], an alternative starting material to [RuCl2(cod)]n for the preparation of ruthenium(II) complexes, has been prepared from the polymer compound and isolated in yields up to 87% using a new work-up procedure. The compound has been obtained as a yellow solid without water of crystallization. The complexes [RuCl2(NCR)2(cod)] spontaneously transform into dimers [Ru2Cl(-Cl)3(cod)2(NCR)] (R¼Me, Ph). 1H NMR kinetic experiments for these
transformations evidenced first-order behavior. [RuCl2(NCPh)2(cod)] dimerizes slower by a factor of ten than [RuCl2(NCCH3)2(cod)]. The following activation parameters, DH#¼114 3 kJ mol1 and DS#¼669 JK1 mol1 for R¼CH3CN (DG#¼945 kJ mol1, 298.15 K) and DH#¼1222 kJ mol1 and DS#¼756JK1 mol1 for R¼Ph (DG#¼1004 kJ mol1,298.15 K), have been calculated from the first-order rate constants in the temperature range
294–323 K. The kinetic parameters are in agreement with a two-step mechanism with dissociation of acetonitrile as the rate-determining step. The molecular structures of [Ru2Cl(- Cl)3(cod)2(NCR)] (R¼Me, Ph) have been determined by X-ray diffraction.