Dehalogenation polycondensation of dihaloorganic compounds with zerovalent nickel complex afforded π-conjugated polymers such as poly(p-phenylene) (PPP) and poly(2,5-thienylene) (PTh) (n X-Ar-X+n Ni (0) L m → (Ar) n + n NiX 2L m) in good yields. PPP and PTh had high crystallinity and doping of powdery PTh with iodine afforded a material with electrical conductivity of 8 S cm −1. Poly(3-hexyl-2,5-thienylene) had degree of polymerization of ca. 500.