EXPERIMENTAL RESULTS INDICATE THAT THE METAL OF THE CATALYST STRONGLY AFFECTS THE KINETICS OF POLYMERIZATION AND THE REGIOREGULARITY OF SYNTHESIZED POLY-3-ALKYLTHIOPHENES IN M (DPPP) CL2 [DPPP: 1, 3-BIS (DIPHENYLPHOSPHINO) PROPANE] CATALYZED POLYMERIZATION OF 2, 5-DIBROMO-3-ALKYLTHIOPHENE MONOMERS. TO MAKE POSSIBLE ANALYZING SUCH EFFECTS IN MORE DETAIL, WE HAVE COMPUTATIONALLY INVESTIGATED ELECTRONIC STRUCTURE OF MOSTLY KNOWN DPPP INCLUDING CATALYSTS, M (DPPP) CL2, WITH M=NI, PD AND PT. TO THIS END, MOLECULAR STRUCTURE, PARTIAL CHARGE OF ATOMS, HOMO-LUMO ENERGY GAPS (DEHOMO-LUMO), AND THE VALUES OF THE ΡB, L1, L2, L3 AND Ñ2ΡB WERE FULLY DETERMINED BY DFT AND AIM ANALYSIS. RESULTS FROM MOLECULAR STRUCTURE ANALYSIS SHOWED THAT, BY REPLACING NI ATOM WITH PD AND PT, M-CL AND M-P BOND LENGTH INCREASE CONSIDERABLY, WHILE CL-M-CL ANGLE DECREASE SLIGHTLY. FURTHERMORE, DEHOMO-LUMO AND PARTIAL CHARGE ON METAL WERE DECREASED BY THIS ORDER NI<PD<PT. IN ADDITION, NI-P SHOWED LESS ELECTROSTATIC CHARACTERISTIC DUE TO LOWER ΡB, WHICH INDICATES MORE COVALENT CHARACTER OF THIS BOND IN NI (DPPP) CL2 CATALYST IN COMPARE WITH PD-P AND PT-P BONDS IN THEIR CORRESPONDING CATALYSTS.

IN THIS STUDY WE HAVE INVESTIGATED COMPUTATIONALLY THE MECHANISM OF POLYMERIZATION OF 2, 5-DIBROMO 3-BUTYLTHIOPHENE (1) VIA GRIM METHOD, WITH A FOCUS ON THE ORIGIN OF THE HEAD TO TAIL (HT) SELECTIVITY. TO THIS END, FIRST GRIGNARD REAGENT UNDERWENT OXIDATIVE ADDITION TO MONOMER (1) TO AFFORD THE 2-BROMO-5-CHLOROMAGNESIO-3-BUTYLTHIOPHENE (INTERMEDIATE I1) OR THE 2-CHLOROMAGNESIO 5-BROMO-3-BUTYLTHIOPHENE (INTERMEDIATE I2) REGIOISOMERS. THE MECHANISM OF POLYMERIZATION OF I1 OR I2 WITH NI (DPPP) CL2 [DPPP: 1, 3-BIS (DIPHENYLPHOSPHINO) PROPANE] CATALYST INVOLVES THREE MAIN CATALYTIC STEPS: OXIDATIVE ADDITION, TRANSMETALATION, AND REDUCTIVE ELIMINATION, WHICH WILL BE STUDIED IN THE PRESENT WORK IN MORE DETAIL.