Effect of solvent on the exchange of ethylene for propylene on cis-PtCl₂(C₃H₆)(TPPTS), TPPTS = P(m-C₆H₄SO₃Na)₃

Abstract

To further understand the effect of water as a solvent in organometallic reactions, the lability of η²-alkenes coordinated to platinum(II) phosphine complexes has been studied in water and chloroform as a comparison of solvent effects on the exchange kinetics and alkene complex stability. ¹H NMR techniques with both deuterated chloroform and a deuterium oxide/deuterated methanol mixture as solvent systems were used at temperatures as low as −50°C. Reaction of cis-PtCl₂L(η²-C₃H₆) [L = PPh₃ (triphenylphosphine) (1a), TPPTS (tris(m-sulfonatophenyl)phosphine) 1b] with ethylene to form cis-PtCl₂L(η²-C₂H₄) (2 a, b) was observed with dependence on the rate by starting platinum complex and ethylene. The role of water on this reaction, as well as its effect on the equilibrium, will be discussed. The equilibrium constant shows preference for coordination of ethylene and the temperature dependence indicates the reaction is entropy controlled.

Keywords:

• Exchange kinetics
• Platinum
• Water as solvent

Acknowledgments

The authors greatly appreciate the careful reading and advice of Professor Jerome B. Keister.