Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States.
J Am Chem Soc. 2022 Jul 27;144(29):13311-13318. doi: 10.1021/jacs.2c04655. Epub 2022 Jul 14.
Cobalt-mediated radical polymerization (CMRP) is a versatile technique for controlling the polymerization of vinyl monomers reversible termination using Co complexes as persistent radical deactivators. Here, we report a facile approach for the generation of Co-H as a discrete initiator and mediator for CMRP of acrylate and acrylamide monomers, overcoming the limitations of existing initiation strategies. oxidation of a Co complex followed by transmetalation with silane generates a Co-H species, which initiates polymerization hydrometalation of the monomer. This method precludes an induction period with excellent control over targeted molecular weight and dispersity. Strikingly, our approach allows complete polymerization when the induction period ends for conventional CMRP. A broad scope of monomers is amenable to this protocol, including acrylates and acrylamides. Tunable catalyst electronics afford tailored dispersity while maintaining agreement in molecular weight in stark contrast to conventional methods. Elimination of this induction period imbues polymerization behavior entirely to the catalyst electronic effects on reversible deactivation/activation rates.
钴介导的自由基聚合（CMRP）是一种通用技术，可控制乙烯基单体的聚合，可逆终止使用 Co 配合物作为持久自由基失活剂。在这里，我们报道了一种简便的方法，可将 Co-H 作为离散引发剂和介体制备丙烯酸酯和丙烯酰胺单体的 CMRP，克服了现有引发策略的局限性。钴配合物的氧化随后与硅烷进行转金属化，生成 Co-H 物种，引发聚合，单体的氢金属化。该方法不存在诱导期，对目标分子量和分散度具有出色的控制。引人注目的是，当传统 CMRP 的诱导期结束时，我们的方法允许完全聚合。该方法适用于多种单体，包括丙烯酸酯和丙烯酰胺。可调谐的催化剂电子给体提供了可调的分散性，同时保持分子量的一致性，与传统方法形成鲜明对比。消除该诱导期使聚合行为完全受催化剂对可逆失活/活化速率的电子效应的影响。
