Increased catalytic activity of cationic palladium(II) complexes on immobilisation in Nafion-H+

Catalytic dimerisation of ethene by [Pd(1,10-phen)2]2+ supported in three forms of Nation has confirmed that diffusion of reactants and/or products through Nation is rate-limiting. However, a combination of low catalyst loading and high dispersion of Nation has resulted in extraordinary increases in ethene dimerisation activities when compared with the homogeneous analogue. Initial activities as high as 760,000 turnovers h-1 have been obtained for the supported complex compared with a homogeneous activity of 32,000 turnovers h-1. These increases in activity most likely result from the very polar, strongly acidic environment in Nation which ensures effective anion-cation separation and promotes labilisation of the nitrogen donor ligands. Enhancements in activities for co-polymerisation of ethene and carbon monoxide, and carbomethoxylation of ethene have also been observed using Nation supported Pd(II) catalysts in methanol.