Structure of Cobalt(II) Ion and Tri- and Tetrachlorocobaltate(II) Complexes in N,N-Dimethylformamide Determined by the Fluorescent EXAFS Method

Abstract

Abstract EXAFS (extended X-ray absorption fine structure) spectra were measured for N,N-dimethylformamide (DMF) solutions containing cobalt(II) ion and its chloro complexes of low concentration (20–40 mmol dm−3) by a laboratory EXAFS spectrometer modified for the fluorescence detection. The analysis of the EXAFS data for a cobalt(II) perchlorate DMF solution showed that cobalt(II) ion in DMF has an octahedral structure with six DMF molecules. The Co-O (DMF) bond length within [Co(dmf)6]2+ in DMF is 206(1) pm and is practically the same as that within [Co(H2O)6]2+ (208 pm) in water within experimental uncertainties. It was also shown that the tri- and tetrachlorocobaltate(II) complexes in DMF have a tetrahedral structure. The Co–O and Co–Cl lengths within [CoCl3(dmf)]− in DMF are 202(1) and 227(1) pm, respectively. The Co–Cl distances within [CoCl]2− in DMF and in water are the same and 229(1) pm.