NOVELTY - Nickel catalyst (I-II), is new.    USE - Nickel catalyst used in optoelectronic device selected form organic thin film transistors, organic light-emitting diodes or organic solar cells (all claimed).    ADVANTAGE - The nickel catalyst has solubility in common organic solvents, longer shelf life without having sensitivity to air and moisture, and is amenable for flow syntheses and ability to produce defect free regioregular poly(3-alkylthiophenes) and other conjugated polymers via Grignard metathesis polymerization (GRIM) with precise control over critical molecular design parameters, and can be prepared in a simple and cost-effective manner.    DETAILED DESCRIPTION - Nickel catalyst of general formulae (I-II), is new.    X=-I, -Br or Cl;    E=S, O -NR;    Y'=-CCMe3Si or 1-20C linear or branched alkyl group or aryl group optionally substituted;    L=1,3-bis(diphenylphosphino)propane or 1,2-bis(diphenylphosphino)ethane;    R=1-20C linear or branched alkyl group or aryl group optionally substituted; and    R'=R as defined above or 1-20C linear or branched alkyl group or aryl group optionally substituted.    INDEPENDENT CLAIMS are included for the following:    (1) a method for preparing nickel catalyst; and    (2) a method for synthesizing polymers, with one equivalent of alkyl Grignard reagent in a suitable solvent optionally in presence of an inorganic salt, and the polymerizing the formed intermediate by adding catalyst in a suitable solvent.    G=CH2CH(R') or CH2C(RR')CH2 group;    Q, Z and E=independently selected from O, -NR, S or Se;    J and M=independently selected from H, R, OR, NRR', SR, SeH or SeR group;    A=selected from optionally substituted ortho, meta or para -pheneylene or optionally substituted 2,7-carbazoles or optionally substituted 3,6-carbazoles or optionally substituted 2,7-fluorenes or optionally substituted 3,6-fluorenes, or optionally substituted 2,7-silafluorenes or optionally substituted 3,6-silafluorenes or optionally substituted 4,7-(21,3-thiadiazole)s, or optionally substituted thieno(3,2-b)thiophenes, or optionally substituted thieno(2,3-b)thiophenes;    R=H or 1-20C linear or branched alkyl group or aryl group optionally substituted or CH2-O-(CH2)A-B;    A=0010;    B'=H or 1-5C linear or branched alkyl or aryl group optionally substituted; and    R', R'' and R'''=R as defined above or 1-20C linear or branched alkyl group or aryl group optionally substituted.