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Experiments in Thermodynamics and Kinetics of Phosphine Substitution in (p-Cymene)RuCl2(PR3)

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Norris W. Hoffman

Department of Chemistry, University of South Alabama, Mobile, AL 36688

Oleg V. Ozerov and Claudia M. Fafard

Department of Chemistry, Brandeis University, Waltham, MA 02454

J. Chem. Educ., 2007, 84 (3), p 489

DOI: 10.1021/ed084p489

Publication Date (Web): March 1, 2007

Abstract

This manuscript describes a set of three experiments that investigates the thermodynamic and kinetic aspects of phosphine substitution at a Ru center. In the first experiment, the students synthesize a Ru organometallic complex containing a phosphine ligand. In the second, equilibria for phosphine substitution involving several different phosphines are studied. The equilibrium constants are converted into free energies of reactions which are compared with data from literature thermochemical studies. In the third experiment, the kinetics of the substitution of tris(p-fluorophenyl)phosphine is studied using variable-temperature (25–60 °C range) ¹⁹F NMR. The kinetic studies confirm that this reaction follows a simple first-order rate law. With some approximations, combining the data obtained here and the literature thermochemical data allow estimation of the strength of a bridging Ru–Cl bond in the starting material used in this laboratory set. The materials used in these experiments are relatively inexpensive and air-stable.