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)
- 1 January 1981
- journal article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 2,p. 501-505
- https://doi.org/10.1039/dt9810000501
Abstract
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– < Cl– < ClO4 –≈ SCN– < picrate. The benzene and the methylene chloride solutions of L1 extract lithium salts selectively from aqueous solutions. In the latter solvent the selectivity factor γ(Li+/Mn+) was found to be 2.5, 44, 216, and 355 for Na+, K+, Mg2+, and Ca2+ 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.Keywords
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