Department of Chemistry, University of Victoria, 3800, Finnerty Road, Victoria, BC, V8P 5 C2, Canada.
Department of Chemistry, University of Eastern Finland, Joensuu Campus, Yliopistokatu 7, 80100, Joensuu, Finland.
Chemphyschem. 2021 Jul 2;22(13):1326-1335. doi: 10.1002/cphc.202100268. Epub 2021 Jun 14.
Density functional theory calculations on neutral sheet models for methylaluminoxane (MAO) indicate that these structures, containing 5-coordinate and 4-coordinate Al, are likely precursors to ion-pairs seen during the hydrolysis of trimethylaluminum (Me Al) in the presence of donors such as octamethyltrisiloxane (OMTS). Ionization by both methide ([Me] ) and [Me Al] abstraction, involving this donor, were studied by polarizable continuum model calculations in fluorobenzene (PhF) and o-difluorobenzene (DFB) media. These studies suggest that low MW, 5-coordinate sheets ionize by [Me Al] abstraction, while [Me] abstraction from Me Al-OMTS is the likely process for higher MW 4-coordinate sheets. Further, comparison of anion stabilities per mole of aluminoxane repeat unit (MeAlO) , suggest that anions such as [(MeAlO) (Me Al) Me] =[7,4] are especially stable compared to higher homologues, even though their neutral precursors are unstable.
通过对甲基铝氧烷（MAO）中性片模型的密度泛函理论计算表明，这些结构中含有 5 配位和 4 配位的铝，它们可能是在供体如八甲基环四硅氧烷（OMTS）存在下三甲基铝（Me Al）水解过程中观察到的离子对的前体。通过极化连续体模型在氟苯（PhF）和邻二氟苯（DFB）介质中研究了涉及该供体的甲化物（[Me]）和[Me Al]的离解。这些研究表明，低 MW、5 配位片通过[Me Al]的离解而电离，而 Me Al-OMTS 中的[Me]离解是更高 MW 4 配位片的可能过程。此外，比较每摩尔铝氧烷重复单元（MeAlO）的阴离子稳定性表明，与更高同系物相比，阴离子如[(MeAlO) (Me Al) Me] =[7,4]特别稳定，尽管它们的中性前体不稳定。
