化学
分子内力
聚合
催化作用
碳负离子
密度泛函理论
配体(生物化学)
共价键
立体化学
戒指(化学)
动力学
结晶学
桥联配体
高分子化学
计算化学
晶体结构
聚合物
有机化学
受体
生物化学
物理
量子力学
作者
Marta Navarro,David González-Lizana,Luis F. Sánchez‐Barba,Andrés Garcés,Israel Fernández,Agustín Lara‐Sánchez,Ana Rodrı́guez
标识
DOI:10.1021/acs.inorgchem.3c02410
摘要
The successful architecture of active catalytic species with enhanced efficiencies is critical for the optimal exploitation of sustainable resources in industrially demanded processes. In this work, we describe the preparation of novel helical heterobimetallic Al/Mg-based complexes of the type [AlMe2(pbpamd–)MgR{κ1-O-(OC4H8O)}] [R = Et (1a), tBu (2a)] as potential catalysts. The design was performed through the sequential addition of the Al fragment to the ligand, followed by the Mg platform, resulting in a planar π-C2N2(sp2)–Al/Mg bridging core between metals. The new heterobimetallic species have been unambiguously characterized by single-crystal X-ray analysis. NOESY, DOSY, and EXSY NMR studies as well as density functional theory calculations corroborate both a rearrangement in solution to scorpionate complexes containing an unprecedented apical carbanion with a direct σ-C(sp3)–Al covalent bond named [{Mg(R)(pbpamd–) Al(Me)2}] [R = Et (1b), tBu (2b)] and an interconversion equilibrium between both isomers. We verified their utility and high efficiency as catalysts in the well-controlled ring-opening polymerization of the biorenewable l- and rac-lactide (LA) at 23 °C, reaching a remarkable turnover frequency value close to 25000 h–1 for rac-LA at this temperature and exerting a significant level of heteroselectivity (Pr = 0.80). Very interestingly, the kinetics demonstrate apparent first-order with respect to the catalyst and LA, which supports a synergic intramolecular cooperation between centers with electronic modulation among them.
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