Naƒon® supported cationic palladium complexes as catalysts (II)

Abstract

A comprehensive investigation of the ability of Naƒon to influence catalytic reactions has been undertaken using the [Pd( 1,10-phen)₂]²⁺ species immobilized in Naƒon—H⁺. The effects of catalyst loading, solvent, substrate, temperature and pressure on catalytic activity have been studied. We have found that whilst the homogeneous [Pd(1,10-phen)₂][p-tolyl-SO₃]₂ model complex dimerizes ethene and propene, and isomerizes 1-butene, Naƒon supported [Pd(1,10-phen)₂]²⁺ effectively dimerizes ethene only. The ethene dimerization activity of the supported catalyst has been found to be highly dependent on catalyst loading and solvent. Rate limitations are overcome at very low catalyst loadings and activities as high or higher than homogeneous activities were obtained. It appears likely that ethene solubility in the reaction solvent, ethene diffusion through Naƒon, Naƒon morphology, and possible steric constraints on the catalyst at high loadings are important factors. The use of water as the reaction solvent resulted in a dramatic increase in the activity of the supported catalyst and adds weight to the argument that cation-anion separation and a non-coordinating anion are important aspects of catalysis using cationic Pd(II) species. Tests with propene and 1 -butene as the feed indicate that the activity of the supported catalyst is limited by the diffusion of these substrates in Naƒon.