Joshi Anuj, Collins Scott, Linnolahti Mikko, Zijlstra Harmen S, Liles Elena, McIndoe J Scott
Department of Chemistry, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada.
C/o Department of Chemistry, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada.
Chemistry. 2021 Jun 16;27(34):8753-8763. doi: 10.1002/chem.202100271. Epub 2021 May 11.
Hydrolysis of trimethylaluminum (Me Al) in polar solvents can be monitored by electrospray ionization mass spectrometry (ESI-MS) using the donor additive octamethyltrisiloxane [(Me SiO) SiMe , OMTS]. Using hydrated salts, hydrolytic methylaluminoxane (h-MAO) features different anion distributions, depending on the conditions of synthesis, and different activator contents as measured by NMR spectroscopy. Non-hydrolytic MAO was prepared using trimethylboroxine. The properties of this material, which contains incorporated boron, differ significantly from h-MAO. In the case of MAO prepared by direct hydrolysis, oligomeric anions are observed to rapidly form, and then more slowly evolve into a mixture dominated by an anion with m/z 1375 with formula [(MeAlO) (Me Al) Me] . Theoretical calculations predict that sheet structures with composition (MeAlO) (Me Al) are favoured over other motifs for MAO in the size range suggested by the ESI-MS experiments. A possible precursor to the m/z 1375 anion is a local minimum based on the free energy released upon hydrolysis of Me Al.
三甲基铝（Me₃Al）在极性溶剂中的水解反应可以通过电喷雾电离质谱法（ESI-MS）进行监测，使用供体添加剂八甲基三硅氧烷[（Me₃SiO）₃SiMe₂，OMTS]。使用水合盐时，水解甲基铝氧烷（h-MAO）具有不同的阴离子分布，这取决于合成条件，并且通过核磁共振光谱法测量其具有不同的活化剂含量。非水解MAO是使用三甲基硼酸酯制备的。这种含有硼的材料的性质与h-MAO有显著差异。在通过直接水解制备MAO的情况下，观察到低聚阴离子迅速形成，然后更缓慢地演变成以m/z 1375的阴离子为主的混合物，其化学式为[（MeAlO）₁₀（Me₂Al）₂Me]⁻。理论计算预测，在ESI-MS实验所建议的尺寸范围内，组成（MeAlO）₁₀（Me₂Al）₂的片状结构比MAO的其他结构单元更受青睐。m/z 1375阴离子的一种可能前体是基于Me₃Al水解时释放的自由能的局部最小值。
