Department of Chemistry, University of Victoria, P. O. Box 3065, Victoria BC V8W 3V6, Canada.
Department of Chemistry, University of Eastern Finland, P. O. Box 111, FI-80101 Joensuu, Finland.
Dalton Trans. 2018 Dec 28;47(48):17291-17298. doi: 10.1039/c8dt04242j. Epub 2018 Nov 27.
Methylalumoxane (MAO) ionizes highly selectively in the presence of octamethyltrisiloxane (OMTS) to generate [MeAl·OMTS] [(MeAlO)(MeAl)Me]. We can take advantage of this transformation to examine the reactivity of a key component of MAO using electrospray ionization mass spectrometry (ESI-MS), and here we describe the reactivity of this pair of ions with other trialkyl aluminum (RAl) components. Using continuous injection methods, we found EtAl to exchange much faster and extensively at room temperature in fluorobenzene (t∼2 s, up to 25 exchanges of Me for Et) than iBuAl (t∼40 s, up to 11 exchanges) or OctAl (t∼200 s, up to 7 exchanges). The exchanges are reversible and the methyl groups on the cation are also observed to exchange with the added RAl species. These results point to the reactive components of MAO having a structure that deviates significantly from the cage-like motifs studied to date.
甲基铝氧烷（MAO）在八甲基环四硅氧烷（OMTS）的存在下高度选择性地离解，生成 [MeAl·OMTS] [(MeAlO)(MeAl)Me]。我们可以利用这种转化，使用电喷雾电离质谱（ESI-MS）来研究 MAO 的关键组成部分的反应性，在这里我们描述了这对离子与其他三烷基铝（RAl）成分的反应性。使用连续注入方法，我们发现 EtAl 在室温下在氟苯中交换得更快、更广泛（t∼2 s，Me 对 Et 的交换高达 25 次），而 iBuAl（t∼40 s，交换高达 11 次）或 OctAl（t∼200 s，交换高达 7 次）。这些交换是可逆的，阳离子上的甲基也被观察到与添加的 RAl 物种交换。这些结果表明 MAO 的反应性成分具有明显偏离迄今为止研究的笼状结构的结构。
