New neutral Ni(II)- and Pd(II)-based initiators for polymerization of styrene

Neutral nickel and palladium σ-acetylide complexes [Ni(CCPh)2(PBu3)2] and [Pd(CCPh)2(PBu3)2] are novel initiators for the polymerization of styrene in CHCl3 over a range of polymerization temperature from 40 to 60 °C. Between them, the nickel catalyst exhibited much higher activity than the palladium catalyst. The polystyrene obtained with Ni(II) initiator was a syndio-rich atactic polymer and its weight-average molecular weight reached 279 000. The mechanism of the polymerization was discussed and a radical mechanism was proposed.