The catalytic activity of a series of group VIII transition metal chlorides and acetylides containing different phosphine ligands: ML2(CdropCC(6)H(5))(2) and ML2Cl2 (M = Co, Ni, Pd and Pt; L = PPh3 and PBu3), towards polymerization of p-diethynylbenzene (p-DEB) is examined. The transition metals exert important effect on the catalytic activity of these complexes. The catalytic activity of these complexes falls in with the following order: Co > Ni > Pd > Pt. The catalytic properties of group VIII transition metal complexes are related to the electron configuration of metal elements. Cobalt and nickel chlorides and acetylides were found to be novel and efficient initiating systems for the polymerization of p-diethynylbenzene. The polymerization proceeds at room temperature to give soluble polymers with weight-average molecular weights as high as 2.2 x 10(4) in yields as high as 85%. The polymer obtained with these catalysts possesses a rich-trans extended pi-conjugated polyene chain structure with the pendent groups of p-C(6)H(4)CdropCH. (C) 2002 Elsevier Science B.V. All rights reserved.