The Structure of Zinc Chloride Complexes in Aqueous Solution

Abstract The structure of zinc chloride complexes with different ratios of chloride to zinc, formed in concentrated ZnCl 2 aqueous solutions, were determined from large-angle X-ray scattering using concentrations of the chloride complexes estimated by complementary Raman spectroscopic measurements. The highest chloro complex, [ZnCl 4 ] 2- , is tetrahedral with a Zn-Cl bond length of 2.294(4) Å. The trichloro complex, [ZnCl 3 ] - , which coordinates one water molecule, is pyramidal with the Cl-Zn-Cl angle 111°. The Zn-Cl and the Zn-H 2 O bonds are 2.282(4) and 1.9 Å, respectively. The two lower complexes, [ZnCl 2 ] and [ZnCl] + , cannot be separated by Raman spectra. The average Zn-Cl distance in these complexes is 2.24 Å, and the average Zn-H 2 O distance is 1.9 Å. In [Zn(H 2 O) 6 ] 2+ the Zn-H 2 O distance is 2.15 Å.