Etude vibrationnelle des associations ioniques dans les solvants aprotiques. 7. Solvatation de (LiNCS)p par les solvants peu polaires

Abstract

Solutions of LiSCN in donor solvent – benzene mixtures have been investigated by solubility measurements and by infrared spectrometry. The state of aggregation of LiSCN has been obtained from the ir spectra in the ν(CN) region 2100–2000 cm−1. The selected solvents (tetrahydrofuran, pyridine, acetone, diethylcarbonate, butylacetate, ethylmethylketone) are more or less associating towards LiSCN. The addition of benzene causes an increase of the associating ability of the solvents. By changing the donor solvent and the amount of benzene it has been possible to obtain the ion pair LiNCS, the dimer (LiNCS)2, and higher aggregates in various proportions. The solvation number of lithium has been measured in solvent vibration regions. Each step of aggregation is accompanied by lithium desolvation. The coordination of lithium in all the species which are formed remains equal to 4, or slightly lower in some cases.