| Abstrakt: |
Reactions of 3,5-dichloropyrazoles and 3,3'-dichloro-5,5'-bipyrazoles with zerovalent nickel complex, Ni(0)Lm, have been studied. In cases of 3,5-dichloro-1,4-dimethylpyrazole and 3,5-dichloro-4-methoxycarbonyl-1-methylpyrazole, only the C(5)–Cl bond of the two C–Cl bonds reacts with Ni(0)Lmto afford novel bis(pyrazolyl)nickel(II) complexes with the intact C(3)–Cl bond in moderate yields. Treatment of the bis(pyrazolyl)nickel(II) complexes with H2SO4gives the new dichloro monomers: 3,3'-dichloro-1,1',4,4'-tetramethyl-5,5'-bipyrazole and its 4,4'-bis(methoxycarbonyl) analogue. These undergo dehalogenative polycondensation to give poly(1,1',4,4'-tetramethyl-5,5'-bipyrazole-3,3'-diyl) (6) and its 4,4'-bis(methoxycarbonyl) analogue (7), respectively. Polymer 6is soluble in formic acid, and gives an intrinsic viscosity of 39 cm3g-1in formic acid, whereas polymer 7is soluble in various organic solvents and has an Mnvalue of 8800 (Mw/Mn= 1.56) as estimated from GPC. They show photoluminescent peaks at the onset position of the respective p–p* absorption bands. |
