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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity??
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Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity??

机译：调整钴电子化合物的配体电子学和外围取代：结构和聚合活性？

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摘要

A series of cobalt salen complexes, where salen represents an N_2O_2 bis-Schiff-base bis-phenolate framework, are prepared, characterised and investigated for reversible-termination organometallic mediated radical polymerisation (RT-OMRP). The salen ligands contain a cyclohexane diimine bridge and systematically altered para-substituted phenoxide moieties as a method to examine the electronic impact of the ligand on complex structure and reactivity. The complexes are characterised by single crystal X-ray diffraction, cyclic voltammetry, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy and computational methods. Structural studies all support a tailorable metal centre reactivity altered by the electron-donating ability of the salen ligand. RT-OMRP of styrene, methyl methacrylate and vinyl acetate is reported and suggests that cobalt–carbon bond strength varies with the ligand substitution. Competing β-hydrogen abstraction affords long-chain olefin-terminated polymer chains and well controlled vinyl acetate polymerisations, contrasting with the lower temperature associative exchange mechanism of degenerative transfer OMRP.
机译：制备，表征和研究了可逆终止有机金属介导的自由基聚合（RT-OMRP）的一系列塞伦钴配合物，其中塞伦代表N_2O_2双席夫碱双酚盐骨架。萨伦配体包含环己烷二亚胺桥和系统地改变的对位取代的酚盐部分，以此作为检查配体对复杂结构和反应性的电子影响的方法。配合物的特征在于单晶X射线衍射，循环伏安法，X射线光电子能谱，电子顺磁共振谱和计算方法。结构研究均支持可调整的金属中心反应性，该反应性可通过Salen配体的供电子能力改变。据报道，苯乙烯，甲基丙烯酸甲酯和乙酸乙烯酯的RT-OMRP值表明钴-碳键强度随配体取代而变化。竞争性的β-氢提取可提供长链烯烃封端的聚合物链，且乙酸乙烯酯的聚合反应得到良好控制，这与变性转移OMRP的低温缔合交换机理形成了鲜明的对比。

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