Elucidation of Structure of the Second Coordination Sphere of Tris(ethylenediamine) Complex by the Isomorphous-Substitution Technique on Solution X-Ray Diffraction

点击翻译按钮获取中文摘要

X-ray diffraction measurements have been carried out for aqueous solutions of chloride, bromide, iodide, perchlorate, and sulfate of tris(ethylenediamine)rhodium(III) and chromium(III) complexes. The radial distribution functions, D^<Rh>(r), around a rhodium atom were derived from the X-ray intensity data in a manner of the isomorphous substitution between Rh and Cr. The following values of metal-ligand intramolecular interactions obtained in this study were almost consistent with the crystarographic results: r_<Rh-N>=2.08A^^ﾟ(n=6) and r_<Rh-c>=2.90-2.95A^^ﾟ(n=6). Beyond 3A^^ﾟ a separated group of peaks attributable to the second coordination-sphere interactions in the vicinity of amino groups of the ligand was appeared in the region of 3.5-5.0A^^ﾟ of each D^<Rh>(r). The anion dependence of these peaks was found to suggest the existence of the anions in contact with the amino group. The peak area in the region of 3.5-5.0A^^ﾟ of D^<Rh>(r) for the perchlorate solution was smaller than th … More at for the chloride solution, while in the region of 5.0-7.5A^^ﾟ the situation was reverse. This means that the associated perchlorate ions exist around the methylene group and do not contribute to the distribution around 3.5-5.0A^^ﾟ. Therefore, the peaks in D^<Rh>(r) of the perchlorate solution were attributed to the hydration water molecules and were and were analyzed by comparing theoretical curves; the water molecules were situated at 3.90A^^ﾟ(n=2.5), 4.34A^^ﾟ(n=4.7), and 4.85A^^ﾟ(n=3.1). Considering this result, D^<Rh>(r) of the bromide and chloride solutions were analyzed and it was proved that the associated bromide ions existed at 4.64A^^ﾟ(n=1) and the chloride ions at 4.50A^^ﾟ(n=1) in both 0.3 M and 0.9 M solutions. These halide ions were considered to be in contact with the amino group by replacing one water molecule situated at 4.34A^^ﾟ. From D^<Rh>(r) of the iodide solution meaningful results were not obtained because of its low concentration(0.06 M) due to poor solubility of the iodide. D^<Rh>(r) of the sulfate solution suggested that the associated sulfate ions were in contact with the amino group with various orientation. Less