EXAFS INVESTIGATION OF INNER-SPHERE AND OUTER-SPHERE CHLOROAQUO COMPLEXES OF CR3-SOLUTIONS( IN AQUEOUS)

The structure of four solutions containing the isolated chromochloroaq uo complexes, [CrCln(H2O)(6-n)]((3-n)+) (n = 1-3), have been investiga ted with the aid of EXAFS. Synthesis and isolation processes are descr ibed. In the inner-sphere complexes, Cr3+ ions are surrounded by 5H(2) O + 1Cl(-) (species [I], 1 m), 4H(2)O + 2Cl(-) (species [II], 1 and 0. 005 m), and 3H(2)O + 3Cl(-) (species [III], 0.005 m), with Cr-O and Cr -Cr average distances of 2.00 and 2.30 Angstrom, respectively. In the four solutions a second coordination sphere is detected between 3.9 an d 4.5 Angstrom. In solution containing species [I], this sphere is for med by water molecules (similar to 14) at 3.97 Angstrom whereas for so lutions containing [II] and [III], several outer-sphere chloride anion s are detected. For species [II] the second coordination sphere is for med by 3.3 (1 m) or 4.9 (0.005 m) chloride ligands, depending upon con centration of the complex, at around 4.3 Angstrom and by 8.0 (1 m) or 7.2 (0.005 m) water molecules at 3.9 a. For species [III], where [HCl] = 12 M, this sphere is formed exclusively by seven chloride ligands a t 4.3 Angstrom.