Catalytic conversions in water Part 14. The alternating copolymerization of ethene and CO catalyzed by water-soluble Pd catalysts

The alternating copolymerization of ethene and carbon monoxide proceeds eff iciently in aqueous media in the presence of the water-soluble Pd/DPPPr-S/H OTs (DPPPr-S: C3H6-1,3-(P(C6H4-m-SO3Na)(2))2, HOTs: p-toluenesulfonic acid) catalyst system. A maximum catalyst activity of 7.7 kg copolymer (g Pd)(-1 ) h(-1) was observed at 90 degrees C and 60 bar. The molecular weights of t he copolymer samples increased with increasing pressure and decreasing temp erature and ranged from M-n=50.0 kg mol(-1) (50 degrees C, 40 bar) to M-n=9 .6 kg mol(-1) (90 degrees C, 40 bar). High reaction rates were observed whe n ethene/CO mixtures richer in CO (optimum at 64% v/v CO) were used, but th e highest molecular weights were obtained when the ethene/CO ratio was 1.0. The water-soluble catalysts containing the water-soluble ligands 1,2-bis(di (m-sodiumsulfonatophenyl)phosphino)pentane (DPPEt-S), 1,4-bis(di(m-sodiumsu lfonatophenyl)phosphino)butane (DPPBu-S) and (s, s) 2,4-bis(di(m-sodiumsulf onatophenyl)phosphino)pentane (2,4-DPPPen-S), having a C2H4, n-C4H8 Or 2.4- n-C5H10 bridge between the phosphorus atoms, respectively, were also tested in the copolymerization. Pd/DPPEt-S/HOTs was less stable, Pd/DPPEt-S/HOTs also exhibited a lower catalyst activity, while Pd/DPPBu-S/HOTs was more ac tive compared to the catalyst system based on DPPPr-S. In all cases, the av erage molecular weights of the products were considerably lower compared to those of samples obtained with Pd/DPPPr-S/HOTs. (C) 2000 Elsevier Science B.V. All rights reserved.