Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
Abstract:
The reversible equilibrium conversion under H2 of [RuCl(dppb) (μ-Cl)]2 (1) to generate (η2-H2) (dppb) (μ-Cl)3RuCl(dppb) in CH2Cl2 (dppb = Ph2P(CH2)4PPh2) has been studied at 0–25 °C by UV-Vis and 31P{1H} NMR spectroscopy, and by stoppe kinetics; the equilibrium constant and corresponding thermodynamic parameters, and the forward and reverse rate constants at 25 °C have been determined. A measured ΔH° value of 0 kJ mol−1 allows for an estimation of an exothermicity of 60 kJ mol−1 for binding an η2-H2 at an Ru(II) centre; a ΔS° value of 60 J mol−1 K−1 indicates that in solution 1 contain s coordinated CH2Cl2. The kinetic and thermodynamic data are compared to those obtained from a previously studied hydrogenation of styrene catalyzed by 1. Preliminary findings on related systems containing Ph2P(CH2)3PPh2 and (C6H11)2P(C6H11)2 are also noted.