R. Mitsuhashi, M. Mikuriya
2016
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X-ray Structure Analysis Online
Abstract
Ethylenediaminetetraacetic acid (H4edta) is a typical chelate ligand, which has attracted much attention over the past five decades because of its usefulness for industrial applications as well as basic study applications such as the chelate titration method. Many metal complexes with the edta ligand have been reported.1 Probably, cobalt(III) complexes are one of the most studied compounds among metal edta complexes. As for X-ray crystallographic studies, NH4, Na+,3,4 Rb+,2 Mg2+,5 Ca2+,5 Sr2+,6 and Ca2+6 salts of [Co(edta)]– were investigated. However, the crystal structure of the potassium salt has not yet been reported. In this study, we isolated a cobalt(III) complex with edta as K+ salt, K[Co(edta)]·2H2O, and determined the crystal structure, as shown in Fig. 1. The present complex was prepared by a method described in the literature.7 Cobalt(II) chloride hexahydrate (2.38 g (0.01 mol), potassium acetate (5.89 g, 0.06 mol), and ethylenediaminetetraacetic acid (2.92 g, 0.01 mol) were dissolved in 15 cm3 of water, and the solution was heated for 30 min. To this solution was added 10 cm3 of a 3% H2O2 solution. The reaction solution was filtered while hot, and the filtrate was concentrated. To this concentrated solution was added 20 mL of ethanol to give a precipitate. The precipitate was collected, washed by ethanol, and dried under a vacuum. Yield, 4.15 g (98%). IR (KBr, cm–1): 3465, 3394, 3279, 2967, 2932, 1653 (nasCOO), 1361 (nsCOO). Absorption spectra: lmax 536 nm (e = 234 M–1 cm–1), 381 nm (e = 158 M–1 cm–1). X-ray quality crystals were grown by the slow diffusion of methanol to the aqueous solution. X-ray diffraction data for these crystals were collected at 293 K on a Bruker CCD X-ray diffractometer (SMART APEX) using graphite-monochromated Mo-Ka radiation. Crystal data and details concerning data collection are given in Table 1. The structure was solved by direct methods, and refined by fullSynthesis and Crystal Structure of Potassium Ethylenediaminetetraacetatocobaltate(III)