Screw-sense-selective polymerization of aryl isocyanides initiated by a Pd-Pt μ-ethynediyl dinuclear complex:: A novel method for the synthesis of single-handed helical poly(isocyanide)s with the block copolymerization technique
Screw-sense-selective polymerization of aryl isocyanides initiated by a Pd-Pt μ-ethynediyl dinuclear complex:: A novel method for the synthesis of single-handed helical poly(isocyanide)s with the block copolymerization technique
复制标题
DOI：
10.1002/(sici)1521-3765(20000317)6:6
复制
发表时间：
2000-03-17
影响因子：
4.3
通讯作者：
Takahashi, S
中科院分区：
文献类型：
--
作者：
Takei, F;Yanai, K;Takahashi, S
手性芳基异氰化物的活性聚合，如间和对甲基羰基苯基异氰化物2和5，由Pd-Pt多-乙炔-二基双核配合物1引发，以高旋感选择性得到聚（异氰化物）s 3和6，由于其螺旋手性，它们具有较大的比旋和在λ = 364nm处的强CD带。所得聚合物3和6的摩尔旋光度和摩尔圆二色性在聚合度（P-n）大于30时达到恒定值。非手性芳基异氰化物具有非常大的取代基，如3,5-二（丙氧羰基）苯基异氰化物（11），3,5-二（丁氧羰基）苯基异氰化物（13）和3.5-二（环己基羰基）苯基异氰化物（15），通过使用手性低聚物配合物3（30）和6(30)，通过1与30等价物2或5的反应，作为引发剂，得到主要的单手螺旋聚合物，实现了螺旋选择性聚合。相比之下，较小的芳基异氰酸酯也被3、和6聚合，在反应的初始阶段具有螺旋选择性，但单手螺旋在高分子量时不能保留。对(L)-和(D)-2，或(L)-和(D)-5与手性低聚物(L)-3（50）或(L)-6（100）聚合的动力学研究表明，聚合物主链的螺旋感不受动力学控制，而是产生了热力学稳定的螺旋感。
Living polymerization of chiral aryl isocyanides, such as m- and p-menthoxycarbonylphenyl isocyanides 2 and 5, initiated by the Pd-Pt mu-ethyne-diyl dinuclear complex 1, proceeds with a high screw-sense selectivity to give the poly(isocyanide)s 3 and 6, which exhibit a large specific rotation and an intense CD band at lambda = 364 nm as a consequence of a helical chirality. The molar optical rotation and molar circular dichroism of the resulting polymers 3 and 6 reach a constant Value at a degree of polymerization (P-n) of more than 30. Screw-sense-selective polymerization of achiral aryl isocyanides that bear very bulky substituents, such as 3,5-di(propoxycarbonyl)phenyl isocyanide (11), 3,5-di(butoxycarbonyl)phenyl isocyanide (13), and 3.5-di(cyclohexyloxycarbonyl)phenyl isocyanide (15), is achieved by the use of chiral oligomer complexes 3(30) and 6(30) prepared from the reaction of 1 with 30 equivalents of 2 or 5, as an initiator to give predominantly single-handed helical polymers. In contrast, smaller aryl isocyanides are also polymerized by 3,, and 6, with screw-sense selectivity in the initial stage of the reaction, but the single-handed helix is not preserved up to high molecular weight. Kinetic studies of the polymerization of (L)- and (D)-2, or (L)- and (D)-5 with chiral oligomer complexes (L)-3(50) or (L)-6(100) suggests that the screw sense of the polymer backbone is not controlled kinetically, but rather that the thermodynamically stable screw sense is produced.