COPOLYMERIZATION OF CYCLOPENTENE AND CARBON-MONOXIDE WITH PALLADIUM CATALYSTS

The alternating copolymerization of cyclopentene with carbon monoxide using palladium catalyst systems of the type [PdX(2)(L(2))] (where (L(2)) is a diphosphine or dinitrogen ligand, and X is a weakly coordinating or non-coordinating anion) is reported. High yields of the copolymer can be obtained in spite of the rather low catalytic activity of these systems. With molecular masses up to 8500 g mol(-1) the chains of these copolymers are short. The enchainment of the olefin comonomer occurs seemingly statistically by 1,2 and 1,3 insertion, the latter insertion type being normally prevailing. Within the copolymers 95/5% regioselectivity towards the 1,3 addition product have been achieved, whereby copolymers with higher contents of 1,3 insertion usually show lower molecular weights. The C-13 spectra of these copolymers are in most cases rather simple even in the region of the carbonyl signal. This region of the spectra does not seem to be particularly sensitive to the regiochemistry of the copolymer. Its narrowness is taken as an indication of stereoregularity of the copolymers, most probably of the isotactic type.