The catalytic activity of a series of nickel acetylides and chlorides containing different phosphine and alkynyl ligands: NiL2(C equivalent to CR)(2); NiL2(C equivalent to CR)Cl and NiL2Cl2 (L-2 = (PPh3)(2), (PBu3)(2) and Ph2PCH2CH2PPh2; R = p-C6H4C equivalent to CH, C6H5. H, CH2OH and CH2OCOCH3), towards p-diethynylbenzene polymerization is compared. The catalytic property of these acetylides is related to chlorine, phosphines and alkynyl ligands bonded to the metal atoms. The polarity, steric hindrance and electron-donating ability of ligands are main factors influencing the catalytic activity of these complexes. Nickel acetylides were found to be novel efficient initiating systems for the alkyne polymerization. The polymerization proceeds under mild conditions to give soluble rr-conjugated polymers with weight average molecular weights as high as 4.8 x 10(4) in yields as high as 95%,