The synthesis of organo‐functionalized polyhedral oligomeric silsesquioxanes (POSS, (R‐SiO_1.5)_n, T_n) is an area of significant activity. To date, T₁₄ is the largest such cage synthesized and isolated as a single isomer. Herein, we report an unprecedented, single‐isomer styryl‐functionalized T₁₈ POSS. Unambiguously identified among nine possible isomers by multinuclear solution NMR (¹H, ¹³C, and ²⁹Si), MALDI‐MS, FTIR, and computational studies, this is the largest single‐isomer functionalized T_n compound isolated to date. A ring‐strain model was developed to correlate the ²⁹Si resonances with the number of 6‐, 5‐, and/or 4‐Si‐atom rings that each non‐equivalent Si atom is part of. The model successfully predicts the speciation of non‐equivalent Si atoms in other families of T_n compounds, demonstrating its general applicability for assigning ²⁹Si resonances to Si atoms in cage silsesquioxanes and providing a useful tool for predicting Si‐atom environments.

中文翻译：

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大型多面体低聚倍半硅氧烷笼：前所未有的Si18O27核心功能化的POSS的隔离。

有机功能化的多面体低聚倍半硅氧烷（POSS，（R-SiO _1.5）_n，T _n）的合成是一个重要的领域。迄今为止，T ₁₄是作为单一异构体合成和分离的最大的此类笼。在本文中，我们报道了史无前例的单一异构体苯乙烯基官能化的T ₁₈ POSS。间通过多核NMR溶液九个可能的异构体（明确地识别¹ H，¹³ C，和²⁹ Si）的，MALDI-MS，FTIR，和计算研究，这是最大的单一异构体官能化Ť _Ñ分离迄今为止化合物。建立了环应变模型以关联²⁹具有每个不等价的Si原子一部分的6、5和/或4-Si原子环的Si共振。该模型成功地预测了其他T _n族化合物中非等价Si原子的形态，证明了其在笼型倍半硅氧烷中为Si原子分配²⁹ Si共振的普遍适用性，并为预测Si原子环境提供了有用的工具。