Comparison of PGSE NMR and ESI-MS Measurements on Methylaluminoxane

IF 6.1 1区 化学 Q1 CHEMISTRY, INORGANIC & NUCLEAR
Luca Rocchigiani, Scott Collins, J. Scott McIndoe, Mikko Linnolahti
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Abstract

PGSE NMR and ESI-MS studies of different grades of hydrolytic MAO demonstrate that the average dimensions and anion distribution of MAO are correlated with one another, as revealed through studies of aging and gelation of a commercial formulation of MAO. Formulations featuring an anion distribution skewed to higher m/z ratios have significantly higher activator contents as measured by 1H NMR spectroscopy in otherwise very similar formulations. PSGE NMR studies in toluene vs. chlorobenzene media demonstrate that the average hydrodynamic dimensions of MAO are largely unaffected by solvent polarity, though aggregation behavior is somewhat sensitive to solvent polarity. As for catalyst activation and ion-pair speciation, the situation in polar solvents is complicated by the formation of solvated cations (and anions) in chlorobenzene which dramatically lower dimensions. DFT studies of model aluminoxane structures in the size range for MAO featuring a variety of architectures, molar mass and Me3Al content reveal that a linear correlation between Dt, as measured by PGSE NMR, can be related to molar mass using simple relationships and estimates of molecular volume if suitable high molecular weight standards are available. There is a reasonable agreement in molar mass with available ESI-MS data, recognizing that MAO is not monodisperse.
对不同等级水解MAO的PGSE NMR和ESI-MS研究表明,MAO的平均尺寸和阴离子分布是相互关联的,这是通过对MAO的老化和凝胶化的研究揭示的。在非常相似的配方中,阴离子分布偏斜于较高的m/z比的配方具有显著较高的活化剂含量。在甲苯和氯苯介质中的PSGE核磁共振研究表明,MAO的平均水动力尺寸在很大程度上不受溶剂极性的影响,尽管聚集行为对溶剂极性有些敏感。至于催化剂的活化和离子对的形成,在极性溶剂中,由于氯苯中溶剂化阳离子(和阴离子)的形成而大大降低了维数,情况变得复杂。对具有多种结构、摩尔质量和Me3Al含量的MAO的尺寸范围内的模型铝氧烷结构的DFT研究表明,如果有合适的高分子量标准,PGSE NMR测量的Dt与摩尔质量之间可以使用简单的关系和分子体积估计之间的线性相关。摩尔质量与可用的ESI-MS数据有合理的一致,认识到MAO不是单分散的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Inorganic Chemistry Frontiers
Inorganic Chemistry Frontiers CHEMISTRY, INORGANIC & NUCLEAR-
CiteScore
10.40
自引率
7.10%
发文量
587
审稿时长
1.2 months
期刊介绍: The international, high quality journal for interdisciplinary research between inorganic chemistry and related subjects
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