Kinetic investigation of a PC(sp3)P pincer palladium (II) complex in the Heck reaction

An investigation of the kinetics of the Heck reaction between 4-iodoanisole and styrene catalysed by {cis-1,3-bis[(di-tert-butylphosphino)methyl]-cyclohexane} palladium (II) iodide (1) has been performed in DMF-d7 solution. Based on mercury poisoning experiments a heterogeneous palladium catalyst formed from the PCsp3PPd(II) pre-catalyst is proposed. Saturation behaviour with respect to the olefin concentration suggests a mechanism consisting of a pre-equilibrium association of the olefin followed by a rate determining reaction with aryl halide. The equilibrium constant for the olefin association, K1, and the rate constant for the subsequent oxidative addition step, k2, were determined to (5.7 ± 2.5) × 10−3 and 18.4 ± 2.7 M−1 s−1, respectively.

An investigation of the kinetics of the Heck reaction catalysed by (1) has been performed in DMF-d7 solution. Based on mercury poisoning experiments a heterogeneous palladium catalyst is proposed. A mechanism consisting of a pre-equilibrium association of the olefin followed by an irreversible reaction with the aryl halide is suggested.Figure optionsDownload as PowerPoint slide