Preparation of a nitrate-coordinated copper(ii) complex of 2-(pyrazol-3-yl)-6-(pyrazolate)pyridine as an efficient catalyst for methyl methacrylate polymerization

摘要

Treatment of [CuCl _2(bppyH _2)] (1, bppyH _2 = 2,6-di(1H-pyrazol-3-yl)pyridine) with 2 equiv. of AgNO _3 in DMF gave rise to a binuclear Cu(ii) complex [Cu _2(bppyH) _2(NO _3) _2] (bppyH = 2-(pyrazol-3-yl)-6-(pyrazolate)pyridine) (2). Complex 2 was characterized by elemental analysis, IR and single crystal X-ray diffraction. Complex 2 has a dimeric structure in which the two Cu(ii) centers are bridged by a couple of the in situ-generated bppyH - anions. Each Cu(ii) center is further coordinated by one O atom of a NO _3 - anion and three N atoms of one bppyH - anion. Complex 2 exhibited a higher catalytic activity in the polymerization of methyl methacrylate (MMA) than the precursor complex 1. Even though the ratio of catalyst to MMA was raised up to 1:1500, the PDI for 2 (reaction time was fixed at 4 h) is 1.63 and the conversion is up to 72%. The effects of solvent, reaction temperature and the ratio of MMA to catalyst were also investigated.