Cobalt(II)–halide association equilibria in ammonium nitrate–dimethyl sulfoxide melts: I. Cobalt(II) chloride

✍ Scribed by Borko Matijević; István J. Zsigrai; Milan Vraneš; Slobodan B. Gadžurić

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 491 KB
• Volume: 154
• Category: Article
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2010.04.003

✦ Synopsis

The cobalt(II)-chloride association equilibria in ammonium nitrate-dimethyl sulfoxide (DMSO) melts of the type NH 4 NO 3 •xDMSO at five different compositions in the range 1.0 ≤ x ≤ 5.0 have been investigated by the spectrophotometric method. Absorption spectra of cobalt(II) chloride solutions containing variable amounts of ammonium chloride at different temperatures from 35 to 65 °C have been recorded in the wavelength range of 400-800 nm. In the absence of chloride, the solutions show spectra typical for octahedral coordination of cobalt (II). Addition of chloride changed the absorption spectra to a tetrahedral or severely distorted octahedral coordination. Stability constants for the complexes [Co(NO 3 ) 2 (DMSO) 2 ], [Co(NO 3 ) 2 X 2 ] 2-and [CoCl 4 ] 2-, and the species spectra for all complexes are reported. The effect of varying the DMSO/NH 4 NO 3 mole ratio is discussed. A sharp increase of the stability constants around x = 2 is correlated to the competition between the solvent molecules or ions and the cobalt(II) ions for the ligand and to the solvation of NH 4 + with two DMSO.