Macaranas Joahanna A, Luke Anna M, Mandal Mukunda, Neisen Benjamin D, Marell Daniel J, Cramer Christopher J, Tolman William B
Currently: Department of Chemistry , Washington University in St. Louis , One Brookings Drive, Campus Box 1134 , St. Louis , Missouri 63130 , United States.
Inorg Chem. 2018 Mar 19;57(6):3451-3457. doi: 10.1021/acs.inorgchem.8b00250. Epub 2018 Feb 27.
Aluminum alkoxide complexes supported by salen ligands [salen = N, N'-bis(salicylaldimine)-2-methylpropane-1,2-diamine or N, N'-bis(salicylaldimine)-2,2-dimethylpropane-1,3-diamine] with o-adamantyl substituents have been synthesized and investigated for the polymerization of ε-caprolactone. Geometric analysis of the catalysts used for the reaction reveals the metal coordination geometries to be intermediate between square-pyramidal and trigonal-bipyramidal. A detailed kinetic study accompanied by density functional theory modeling of key mechanistic steps of the reaction suggest that, in addition to the length of the backbone linker, the o-aryl substituents have a significant impact on the catalyst's reactivity. Bulky ortho substituents favorably distort the precatalyst geometry and thereby foster the achievement of the rate-limiting transition-state geometry at low energetic cost, thus accelerating the reaction.
已合成了由具有邻金刚烷基取代基的salen配体（salen = N，N'-双（水杨醛亚胺）-2-甲基丙烷-1,2-二胺或N，N'-双（水杨醛亚胺）-2,2-二甲基丙烷-1,3-二胺）支撑的烷氧基铝配合物，并对其用于ε-己内酯聚合反应进行了研究。对反应所用催化剂的几何分析表明，金属配位几何结构介于四方锥和三角双锥之间。一项详细的动力学研究以及对反应关键机理步骤的密度泛函理论建模表明，除了主链连接基的长度外，邻芳基取代基对催化剂的反应活性有显著影响。庞大的邻位取代基有利地扭曲了前催化剂的几何结构，从而以较低的能量成本促进了限速过渡态几何结构的实现，从而加速了反应。
