美国埃克森美孚科技公司Alexander V. Zabula团队报道了甲基铝氧烷（MAO）的结构——用于预催化剂活化的可萃取[Al(CH₃)₂]⁺。相关研究成果发表在2024年6月28日出版的《科学》。

甲基铝氧烷（MAO）被用作百万吨级商业聚烯烃生产的预催化剂活化剂，但其精确的结构和相关的活化机制一直是40多年来的一个基本研究难题。

该文中，研究人员报道了活性MAO组分的晶体学表征，揭示了一个离散的二维片状团簇[Al₃₃O₂₆(CH₃)₄₇][Al(CH₃)₃]₂。该结构数据与活性位点带有配位的Al(CH₃)₃并为预催化剂活化提供[Al(CH₃)₂]⁺的假设一致。

量子化学计算揭示了[Al(CH₃)₂]⁺提取的最优选位点（吉布斯自由能的变化为0.0千卡/摩尔）。在结晶MAO活化的茂金属上进行的烯烃聚合试验显示出比商业MAO更高的活性。

附：英文原文

Title: Structure of methylaluminoxane (MAO): Extractable [Al(CH3)2]+ for precatalyst activation

Author: Lubin Luo, Jarod M. Younker, Alexander V. Zabula

Issue&Volume: 2024-06-28

Abstract: Methylaluminoxane (MAO) is used as a precatalyst activator for million ton–scale production of commercial polyolefins, but its precise structure and associated activation mechanisms have been a fundamental research puzzle for more than 40 years. We report here the crystallographic characterization of an active MAO component, which reveals a discrete two-dimensional sheet cluster [Al33O26(CH3)47][Al(CH3)3]2 featuring two trimethylaluminum units, Al(CH3)3, coordinated to two unsaturated aluminum sites. Our structural data are consistent with the hypothesis that the active sites bear coordinated Al(CH3)3 and provide [Al(CH3)2]+ for precatalyst activation. Quantum chemical calculations revealed the most preferred sites for [Al(CH3)2]+ abstraction (a change in Gibbs free energy of 0.0 kilocalories per mole). Olefin polymerization tests on metallocenes activated with the crystallized MAO show higher activities than with the commercial MAO.

DOI: adm7305

Source: https://www.science.org/doi/10.1126/science.adm7305