Photooxidative Generation of Dodecaborate-Based Weakly Coordinating Anions
Photooxidative Generation of Dodecaborate-Based Weakly Coordinating Anions
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DOI：
10.1021/acs.inorgchem.9b00935
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发表时间：
2019-08-19
影响因子：
4.6
通讯作者：
Spokoyny, Alexander M.
中科院分区：
文献类型：
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作者：
Axtell, Jonathan C.;Messina, Marco S.;Spokoyny, Alexander M.
在可见光引发苯乙烯家族聚合的实验和计算研究中引入了类型为B-12（OCH 2 Ar）（12）[Ar = C6 F5（1）、4-CF 3C 6 H4（2）、3，5-（CF 3）（2）C6 H3（3）]的氧化还原活性前阴离子。中性的、空气稳定的前阴离子1-3被发现在蓝光照射下通过单电子氧化引发苯乙烯聚合，产生数均分子量（M-n）在6至100 kDa范围内的聚合物。在大多数实验中观察到较短的聚合物产物，除了在苯乙烯单体上含有4-X（X = F，Cl，Br）取代基的单体的情况下，当在CH 2Cl 2中1的存在下聚合时。仅在这些特定条件下观察到较长的聚合物（>100 kDa），这强烈支持反应条件显著调节十二硼酸根阴离子和阳离子链端之间的离子配对程度的表述。这也表明1-3在单电子还原时表现为弱配位阴离子（WCA），因为在所分析的聚合物产物中没有观察到基于簇的光引发剂的掺入。总的来说，这项工作是一个概念性的实现，一个单一的试剂，可以作为一个强大的光氧化剂，随后形成一个WCA。
Redox-active proanions of the type B-12(OCH2Ar)(12) [Ar = C6F5 (1), 4-CF3C6H4 (2), 3,5-(CF3)(2)C6H3 (3)] are introduced in the context of an experimental and computational study of the visible-light initiated polymerization of a family of styrenes. Neutral, air stable proanions 1-3 were found to initiate styrene polymerization through single-electron oxidation under blue-light irradiation, resulting in polymers with number-average molecular weights (M-n) ranging from similar to 6 to 100 kDa. Shorter polymer products were observed in the majority of experiments, except in the case of monomers containing 4-X (X = F, Cl, Br) substituents on the styrene monomer when polymerized in the presence of 1 in CH2Cl2. Only under these specific conditions are longer polymers (>100 kDa) observed, strongly supporting the formulation that reaction conditions significantly modulate the degree of ion pairing between the dodecaborate anion and cationic chain end. This also suggests that 1-3 behave as weakly coordinating anions (WCA) upon one-electron reduction because no incorporation of the cluster-based photoinitiators is observed in the polymeric products analyzed. Overall, this work is a conceptual realization of a single reagent that can serve as a strong photooxidant, subsequently forming a WCA.