Multinuclear NMR study of the solution structure and reactivity of tris(trimethylsilyl)methyllithium and its iodine ate complex.
Multinuclear NMR study of the solution structure and reactivity of tris(trimethylsilyl)methyllithium and its iodine ate complex.
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三（三甲基硅基）甲基锂及其碘配合物的溶液结构和反应性的多核核磁共振研究。
DOI：
10.1021/jo802032d
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Plessel,KristinN
中科院分区：
文献类型：
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作者：
Reich,HansJ;Sikorski,WilliamH;Sanders,AaronW;Jones,AmandaC;Plessel,KristinN
三(三甲基甲硅烷基)甲基衍生物(1-X)的极端空间体积为研究提供了有趣的结构和动态行为。对 1-SePhand1-I 的动态 NMR 研究表明，每个三甲基甲硅烷基的 C−Si 键周围的旋转受到限制。对天然丰度和 6Li 和 13C 富集 1-Li 进行的广泛多核 NMR 研究揭示了含 THF 溶剂中的三种物质：二聚体 1T 和两种单体、接触离子对 1C 和溶剂分离离子对 1S。观察到的 1-Li 聚集体相互转化的障碍异常高（1S 和 1C 交换的 ΔG⧧ca. 9 kcal/mol，1T 与 1C 和 1S 交换的 ΔG⧧41= 16.4 kcal/mol），允许单独研究每种聚集体的反应性。我们可以证明，1S 对 MeI 的反应性至少是 1C 的 50 倍，并且至少是 1T 的 5 × 1010 倍。反应活性的巨大差异允许进一步研究 1-I 与 1-Li 的锂-碘交换机制以及中间体碘配合物的表征4。对灵敏但化学惰性的 13 C NMR 化学位移温度计 1-H 进行了额外的校准。
The extreme steric bulk oftris(trimethylsilyl)methyl derivatives (1-X) provides interesting structural and dynamic behavior for study. Dynamic NMR studies on1-SePhand1-Ishowed restricted rotation around the C−Si bonds of each trimethylsilyl groups. An extensive multinuclear NMR study of natural abundance and6Li and13C enriched1-Lirevealed three species in THF-containing solvents, a dimer1T, and two monomers, the contact ion pair1C, and solvent separated ion pair1S. Observed barriers for interconversion of1-Liaggregates were unusually high (ΔG⧧ca. 9 kcal/mol for exchange of1Sand1C, ΔG⧧41= 16.4 kcal/mol for exchange of1Twith1Cand1S), allowing for study of reactivity of each aggregate individually. We can show that1Sis at least 50 times as reactive as1Cand at least 5 × 1010times as reactive as1Ttoward MeI. The large difference in reactivity allowed further study on the mechanism of the lithium−iodine exchange of1-Iwith1-Liand characterization of the intermediate iodine ate complex4. Additional calibrations are presented for the sensitive yet chemically inert13C NMR chemical shift thermometer1-H.