Halogen effects on phenylethynyl palladium(II) complexes for living polymerization of isocyanides: a combined experimental and computational investigation

Phenylethynyl palladium(II) complexes have proven to be effective catalysts for coordination polymerization of isocyanides. In this work, two new phenylethynyl palladium(II) initiators bearing bromide (1b) and iodide (1c) were synthesized and applied for living polymerization of aryl and alkyl isocyanides. The coordinated halogen anions can significantly influence the kinetics of polymerization, with the observed order of reaction rates being 1c (I)>1b (Br)>1a (Cl). Impressively, 1c not only accelerates the reaction rate in both the initiation stage and propagation stage, but also can polymerize less active monomers that cannot be reacted by 1a. DFT calculations were then employed to understand the detailed mechanism and the halogen effects in this insertion polymerization process.

苯乙炔基钯(II)配合物已被证明是异腈配位聚合的有效催化剂。在这项工作中，合成了两种带有溴离子（1b）和碘离子（1c）的新型苯乙炔基钯(II)引发剂，并将其应用于芳基和烷基异腈的活性聚合。配位的卤素阴离子能显著影响聚合动力学，观察到的反应速率顺序为1c（I）>1b（Br）>1a（Cl）。令人印象深刻的是，1c不仅在引发阶段和增长阶段都加快了反应速率，而且还能使1a无法反应的活性较低的单体发生聚合。随后采用密度泛函理论（DFT）计算来了解这种插入聚合过程的详细机理和卤素效应。