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Correlation between the Li-6, N-15 coupling constant and the coordination number at lithium

机译：Li-6，N-15耦合常数与锂配位数之间的相关性

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摘要

The (LiN)-Li-6-N-15 coupling constants of lithium amide dimers and their mixed complexes with n-butyllithium, formed from five different chiral amines derived from (S)-[N-15]phenylalanine, were determined in diethyl ether (Et2O), tetrahydrofuran (THF) and toluene. Results of NMR spectroscopy studies of these complexes show a clear difference in Li-6,N-15 coupling constants between di-, tri- and tetracoordinated lithium atoms. The lithium amide dimers with a chelating ether group exhibit Li-6 N-15 coupling constants of similar to 3.8 and similar to 5.5 Hz for the tetracoordinated and tricoordinated lithium atoms, respectively. The lithium amide dimers with a chelating thioether group show distinctly larger Li-6, N-15 coupling constants of similar to 4.4Hz for the tetracoordinated lithium atoms, and the tricoordinated lithium atoms have smaller Li-6 N-15 coupling constants, -4.9 Hz, than their ether analogues. In diethyl ether and tetrahydrofuran, mixed dimeric complexes between the lithium amides and n-butyllithium are formed. The tetracoordinated lithium atoms of these complexes 15 have Li-6, N-15 coupling constants of similar to 4.0 Hz, and the Li-6, N-15 coupling constants of the tricoordinated lithium atoms differ somewhat, depending on whether the chelating group is an ether or a thioether; similar to 5.1 and similar to 4.6Hz, respectively. In toluene, mixed trimeric complexes are formed from two lithium amide moieties and one n-butyllithium. In these trimers, two lithium atoms are tricoordinated with Li-6, N-15 coupling constants of similar to 4.6 Hz and one lithium is dicoordinated with Li-6, N-15 coupling constants of similar to 6.5 Hz.
机译：在二乙基乙基酯中测定了酰胺酰胺二聚​​体及其与正丁基锂的混合配合物的（LiN）-Li-6-N-15偶联常数，由五种不同的衍生自（S）-[N-15]苯基丙氨酸的手性胺形成醚（Et 2 O），四氢呋喃（THF）和甲苯。这些络合物的NMR光谱研究结果表明，二配位，三配位和四配位的锂原子之间的Li-6，N-15偶联常数存在明显差异。具有螯合醚基的氨基酰胺锂二聚体对于四配位和三配位的锂原子表现出分别类似于3.8和5.5Hz的Li-6N-15偶联常数。具有螯合硫醚基的酰胺酰胺锂二聚体对于四配位的锂原子显示出明显更大的Li-6，N-15耦合常数，类似于4.4Hz，三配位的锂原子具有较小的Li-6 N-15耦合常数，-4.9 Hz，比其以太类似物。在乙醚和四氢呋喃中，在酰胺酰胺和正丁基锂之间形成混合的二聚配合物。这些络合物15的四配位的锂原子具有与4.0Hz相似的Li-6，N-15的耦合常数，并且三配位的锂原子的Li-6，N-15的耦合常数根据螯合基团是否为正而有所不同。醚或硫醚;分别类似于5.1和4.6Hz。在甲苯中，混合的三聚体配合物由两个锂酰胺基团和一个正丁基锂形成。在这些三聚体中，两个锂原子与Li-6，N-15的耦合常数三配位，近似于4.6 Hz，一个锂原子与Li-6，N-15的耦合常数，近似6.5 Hz。

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