THE STRUCTURE OF ZINC-CHLORIDE COMPLEXES IN AQUEOUS-SOLUTION

The structure of zinc chloride complexes with different ratios of chlo ride to zinc, formed in concentrated ZnCl2 aqueous solutions, were det ermined from large-angle X-ray scattering using concentrations of the chloride complexes estimated by complementary Raman spectroscopic meas urements. The highest chloro complex, [ZnCl4](2-) is tetrahedral with a Zn-Cl bond length of 2.294(4) Angstrom. The trichloro complex, [ZnCl 3](-), which coordinates one water molecule, is pyramidal with the Cl- Zn-Cl angle 111 degrees. The Zn-Cl and the Zn-H2O bonds are 2.282(4) a nd 1.9 Angstrom, respectively. The two lower complexes, [ZnCl2] and [Z nCl](+), cannot be separated by Raman spectra. The average Zn-Cl dista nce in these complexes is 2.24 Angstrom, and the average Zn-H2O distan ce is 1.9 Angstrom. In [Zn(H2O)(6)](2+) the Zn-H2O distance is 2.15 An gstrom.