Nuclear Magnetic Resonance Study of the Stoichiometry and Stability of Several Li+-Crown Ether Complexes in Various Acetonitrile-Nitrobenzene Mixtures

Lithium‐7 NMR spectrometry was used to study the complexation reaction between lithium ions and several 12‐, 15‐ and 18‐membered crown ethers in a number of binary acetonitrile‐nitrobenzene mixtures. Formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift‐mole ratio data. There is an inverse relationship between the complex stability and the amount of acetonitrile in the mixed solvent. Among different sized crown ethers used, 15‐crowns were found to form the most stable Li+ complexes in the series. The influence of substitution on the macrocyclic rings on the stability of the resulting complexes is discussed.