<br>六甲基二硅氮化钾 (KHMDS)：溶剂依赖性溶液结构,Journal of the American Chemical Society

当前位置： X-MOL 学术 › J. Am. Chem. Soc. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

六甲基二硅氮化钾 (KHMDS)：溶剂依赖性溶液结构
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2024-06-20 , DOI: 10.1021/jacs.4c03418
Jesse A Spivey ₁ , David B Collum ₁

Affiliation

使用多种分析方法（包括²⁹ Si NMR 光谱和密度泛函理论计算）检查了六甲基二硅氮化钾 [KHMDS] 和标记的 [ ¹⁵ N]KHMDS 的溶液结构。 ¹⁵ N- ²⁹ Si 耦合、 ²⁹ Si 化学位移和连续变化方法的组合揭示了二聚体、单体和离子对。弱配位单官能配体如甲苯、 N,N-二甲基乙胺和Et ₃ N仅提供二聚体。 1,3-二氧戊环、THF、二甲氧基乙烷、六甲基磷酰胺和二甘醇二甲醚在低配体浓度下提供二聚体，在高配体浓度下提供单体。 N,N,N',N'-四甲基乙二胺和N,N,N',N'-四甲基环己二胺在环境温度下在所有配体浓度下仅提供二聚体，在-80°C下提供显着的单体。 12-crown-4的研究遇到了技术问题。等摩尔的 15-crown-5 形成二聚体，而过量的 15-crown-5 则提供假定的离子对。等摩尔的 18-crown-6 也提供二聚体，过量则提供单体而不是溶剂分离的离子对。 [2.2.2]穴状配体提供了被认为是接触离子配对穴状化合物。主要使用密度泛函理论 (DFT) 计算来探讨溶剂化。热校正能量与低温下较低的聚集体和较高的溶剂化物一致，但计算出的温度依赖性的幅度远大于实验得出的数据。

"点击查看英文标题和摘要"

Potassium Hexamethyldisilazide (KHMDS): Solvent-Dependent Solution Structures

Solution structures of potassium hexamethyldisilazide [KHMDS] and labeled [¹⁵N]KHMDS were examined using a number of analytical methods including ²⁹Si NMR spectroscopy and density functional theory computations. A combination of ¹⁵N–²⁹Si couplings, ²⁹Si chemical shifts, and the method of continuous variations reveals dimers, monomers, and ion pairs. Weakly coordinating monofunctional ligands such as toluene, N,N-dimethylethylamine, and Et₃N afford exclusively dimers. 1,3-Dioxolane, THF, dimethoxyethane, hexamethylphosphoramide, and diglyme provide dimers at low ligand concentrations and monomers at high ligand concentrations. N,N,N′,N’-Tetramethylethylenediamine and N,N,N′,N’-tetramethylcyclohexanediamine provide exclusively dimers at all ligand concentrations at ambient temperatures and significant monomer at −80 °C. Studies of 12-crown-4 ran into technical problems. Equimolar 15-crown-5 forms a dimer, whereas excess 15-crown-5 affords a putative ion pair. Whereas equimolar 18-crown-6 also affords a dimer, an excess provides a monomer rather than a solvent-separated ion pair. [2.2.2]cryptand affords what is believed to be a contact-ion-paired cryptate. Solvation was probed using largely density functional theory (DFT) computations. Thermally corrected energies are consistent with lower aggregates and higher solvates at low temperatures, but the magnitudes of the computed temperature dependencies were substantially larger than the experimentally derived data.

更新日期：2024-06-20

点击分享查看原文

点击收藏

阅读更多本刊新发论文本刊介绍/投稿指南