The 13C and 7Li NMR spectra of the title adducts were observed in THF. In a temperature range from 20 to −80 °C the adducts existed as contact ion pairs in THF. Below −70 °C, the adduct derived from pyridine or 4-phenylpyridine showed three 7Li signals related to three different associated species in solutions. On the other hand, the adduct derived from 2- or 3-phenylpyridine did not give such multiplet signals at −70 °C. The results are related to the interaction between nitrogen and lithium, and the extent of negative-charge migration into the substituent (phenyl ring) in the adduct.
在
四氢呋喃中观察到了标题加合物的 13C 和 7Li NMR 光谱。在 20 至 -80 °C 的温度范围内,加合物在 THF 中以接触离子对的形式存在。温度低于 -70 ℃ 时,由
吡啶或
4-苯基吡啶衍生的加合物显示出三个 7Li 信号,分别与溶液中三个不同的相关物种有关。另一方面,由 2-或
3-苯基吡啶衍生出的加合物在-70 °C时则不会出现这种多重信号。这些结果与氮和
锂之间的相互作用以及负电荷迁移到加合物中取代基(苯基环)的程度有关。