The effect of the electronegativity of donor atoms in coordinated beta-diketonato ligands on the chromatographic behaviour metal complexes
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The effect on chromatographic behavior, on thin layers of silica gel, of the electronegativity of ligator atoms has been studied for three series of beta-diketonato complexes of the type [M(acac(3-n)(phac-phac)(n)], [M(acac)(3-n)(phacphSac)(n)], and [M(acac)(3-n)(phSacphSac)(n)] (where M represents cobalt(III), chromium(III) or ruthenium(III), acac is the 2,4-pentanedionato ion, phacphac is the 1,3-diphenyl-1,3-propanedionato ion, phacphSac is 3-mercapto-1,3-diphenyl-rop-2-en-1-one, phSacphSac is the 3-mercapto-1,3-diphenyl-prop-2-en-1-tion ion, and n = 0-3). For chromatographic separations, ten typical normal-phase mobile phases were used, five mono-component and five two-component. For all the complexes examined it was found that substitution of the donor oxygen atom by a less electronegative sulfur atom resulted in increased mobility of the complex. It was also established that substitution of the acac ligand resulted in increased hR(F) values. For all the complexes examined a linea...r dependence was observed between the R-M values of the complexes and the number of acac ligands substituted by phSacphSac ligands. On the basis of these results, possible separation mechanisms are discussed.
Keywords:thin-layer chromatography / silica gel / beta-diketonato complexes / ligand substituents / donor atom electronegativity
Source:Journal of Planar Chromatography: Modern TLC / Thin Layer Chromatography, 2004, 17, 4, 250-254
- Research Inst Medicinal Plants, Budakalasz