Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States.
J Org Chem. 2013 Dec 6;78(23):11733-46. doi: 10.1021/jo401740g. Epub 2013 Nov 13.
We report the development of isotopic-labeled (13)C diffusion-ordered NMR spectroscopy (DOSY) NMR with diffusion coefficient-formula weight (D-FW) analysis and its application in characterizing the aggregation state of methyllithium aggregates and complexes with several widely used diamines. Commercially available (13)C-labeled benzene and several easily synthesized (13)C-labeled compounds using (13)C-labeled iodomethane as the isotopic source are developed as internal references for diffusion-formula weight analysis (D-FW). The technique greatly expands the applicability of DOSY D-FW analysis to a much wider variety of compounds because of isotopic labeling. These results reveal that methyllithium exists as a tetrasolvated tetramer in diethyl ether and exclusively as bis-solvated dimers with chelating diamines.
我们报告了（13）C 扩散有序 NMR 光谱（DOSY）NMR 的同位素标记的发展及其与扩散系数-分子量（D-FW）分析的结合，以及在表征甲基锂聚集体和几种广泛使用的二胺的配合物的聚集状态中的应用。商业上可获得的（13）C 标记的苯和几种使用（13）C 标记的碘甲烷作为同位素源的容易合成的（13）C 标记的化合物被开发为扩散分子量分析（D-FW）的内部参考。由于同位素标记，该技术极大地扩展了 DOSY D-FW 分析的适用性，使其适用于更多种类的化合物。这些结果表明，甲基锂在二乙醚中以四配位的四聚体存在，而与螯合二胺则仅以双配位的二聚体存在。
