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Aggregation of perchlorates in aprotic donor solvents. Part 1.—Lithium and sodium perchlorates

1996; Royal Society of Chemistry; Volume: 92; Issue: 21 Linguagem: Inglês

10.1039/ft9969204199

1364-5455

Martial Chabanel, D. Legoff, Khlifa Touaj,

Molecular Sensors and Ion Detection

Non-aqueous solutions of lithium and sodium perchlorates have been investigated by IR and Raman spectroscopy. The 35ClO4 and 37ClO4 isotopomers induce an asymmetry or a splitting of ν3 and ν4 bands. All spectra are interpreted by assuming that the bands of possible solvent-separated species are at the same wavenumbers as if they were free ions ('spectroscopically free ions'). In ionizing solvents (dimethylsulfoxide, N,N-dimethylformamide, acetonitrile or acetone) these perchlorates are partly or completely dissociated into free ions while in associating solvents (esters, cyclic ethers or nitromethane) LiClO4 is in part dimerized. In nitromethane, LiClO4 ion pairs are slightly dissociated into free ions at low concentrations and dimerized at high concentrations. The coordination of ClO4 in the ion pairs is either monodentate (LiClO4) or bidentate (NaClO4). Both ClO4 groups in the LiClO4 dimer are linked by two lithium bridges into a centrosymmetrical structure.