Catalyst-transfer polycondensation. Mechanism of Ni-catalyzed chain-growth polymerization leading to well-defined poly(3-hexylthiophene)

被引:510
作者
Miyakoshi, R [1 ]
Yokoyama, A [1 ]
Yokozawa, T [1 ]
机构
[1] Kanagawa Univ, Dept Appl Chem, Kanagawa Ku, Yokohama, Kanagawa 2218686, Japan
关键词
D O I
10.1021/ja0556880
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
We studied the mechanism of the chain-growth polymerization of 2-bromo-5-chloromagnesio3-hexylthiophene (1) with Ni(dppp)Cl-2 [dppp = 1,3-bis(diphenylphosphino)propane], in which head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a low polydispersity is obtained and the M-n is controlled by the feed ratio of the monomer to the Ni catalyst. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that the HT-P3HT uniformly had a hydrogen atom at one end of each molecule and a bromine atom at the other. The reaction of the polymer with aryl Grignard reagent gave HT-P3HT with aryl groups at both ends, which indicates that the H-end was derived from the propagating Ni complex. The degree of polymerization and the absolute molecular weight of the polymer could be evaluated from the H-1 NMR spectra of the Ar/Ar-ended HT-P3HT, and it was found that one Ni catalyst molecule forms one polymer chain. Furthermore, by reaction of 1 with 50 mol % Ni(dppp)Cl-2, the chain initiator was found to be a bithiophene-Ni complex, formed by a coupling reaction of 1 followed by insertion of the Ni(0) catalyst into the C-Br bond of the dimer. On the basis of these results, we propose that this chain-growth polymerization involves the coupling reaction of 1 with the polymer via the Ni catalyst, which is transferred intramolecularly to the terminal C-Br bond of the elongated molecule. We call this mechanism "catalyst-transfer polycondensation".
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页码:17542 / 17547
页数:6
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