Complexation and Solvent Extraction of Lithium Salts with 2,3,6,7,9,10-Hexahydro-5H-1,4,8,11-benzotetraoxacyclotridecin (Benzo-13-crown-4)

Article abstract of DOI:10.1039/DT9810000501

Solubility measurements were conducted in order to compare the affinity towards lithium salts of several 12- to 16-membered ring 'crown' ethers.The 13-membered ring benzo-13-crown-4 (L¹) was found to be the most effective complexing agent for lithium among the investigated macrocyclic ethers.The effect of counter ions on the solubility was found to be OH(1-) < Cl(1-) < ClO4(1-) ca.SCN(1-) < picrate.The benzene and the methylene chloride solutions of L¹ extract lithium salts selectively from aqueous solutions.In the latter solvent selectivity factor γ(Li(1+)/M(n+)) was found to be 2.5, 44, 216, and 355 for Na(1+), K(1+), Mg(2+), and Ca(2+) respectively.Hydrogen-1 n.m.r. measurements for the solutions of the lithium complexes of L¹ indicate that a planar conformation of the quadridentate macrocyclic ring seems to be favoured in the complexed L¹. The 1 : 1 complexes have been found to be dominant in all investigated solvent systems.However, in methylene chloride and in nitromethane the 2 : 1 'sandwich' type complexes could also be detected.The stability constants of the complexes were found to increase in order of decreasing donicity of the solvent media.

Full text of DOI:10.1039/DT9810000501

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