Advances in Structural Studies on Alkylaluminum Species in the Solid State via Challenging ²⁷Al–¹³C NMR Spectroscopy and X‑ray Diffraction

Advanced multinuclear solid state NMR experiments were developed to probe the structure of two organometallic aluminum derivatives, Li­[Al­(CH3)3CH2Si­(CH3)3] (1) and Li­[Al­(CH3)4] (2), which are relevant to olefin polymerization processes. For the first time, NMR observation of 27Al–13C covalent bonds in solids is performed with the natural abundance material 1. Unprecedented triple-resonance (1H–13C–27Al) and quadruple-resonance (1H–7Li–13C–27Al) heteronuclear correlation two-dimensional NMR experiments are also introduced to probe 27Al–13C and 13C–7Li proximities for 2. High-resolution solid-state NMR spectra thus obtained provide information on the local structure of these representative organometallic derivatives that proved to be most complementary and in full agreement with the structures obtained by X-ray diffraction.本研究研发了先进的多核固体核磁共振（Nuclear Magnetic Resonance, NMR）实验技术，用以探究两种有机金属铝衍生物——Li[Al(CH₃)₃CH₂Si(CH₃)₃]（化合物1）与Li[Al(CH₃)₄]（化合物2）的结构，这两种衍生物与烯烃聚合工艺密切相关。本研究首次以天然丰度的化合物1为样本，实现了固体状态下27Al–13C共价键的核磁共振观测。本次研究还首次提出了前所未有的三共振（1H–13C–27Al）与四共振（1H–7Li–13C–27Al）异核相关二维核磁共振实验技术，用以探究化合物2的27Al–13C与13C–7Li原子间的邻近关系。通过上述实验获得的高分辨固体核磁共振谱图，可为这两类典型有机金属铝衍生物的局域结构提供有效信息，所得结果与X射线衍射得到的结构具有高度互补性且完全一致。