Copolymerization of ethylene and vinyl fluoride by (phosphine-sulfonate)Pd(Me)(py) catalysts

The Pd-II complexes [PO]Pd(Me)(py) (1a-c; [PO] = 2-PAr2-4-Me-benzenesulfonate); Ar = 2-Et-Ph (a), 2-OMe-Ph (b), Ph (c)) catalyze the copolymerization of ethylene and vinyl fluoride in toluene at 80 0 C to produce fluorinated polyethylene. Low levels (0.1-0.5 mol %) of vinyl fluoride incorporation are observed. At 80 psi vinyl fluoride and 220 psi ethylene, la produces a linear copolymer with M-w = 35000, M-w/M-n = 3.0, and 0.17 mol % vinyl fluoride incorporation. At a total pressure of 300 psi, increasing the proportion of vinyl fluoride in the feed results in an increase in the level of vinyl fluoride incorporation (to 0.45 mol %) and a decrease in polymer yield and molecular weight. la is more reactive and produces higher molecular weight copolymer than 1b,c, but all three catalysts incorporate similar levels of vinyl fluoride. Control experiments rule out a radical copolymerization mechanism, and an insertion mechanism is proposed.