Hydration of the Yttrium(III) Ion in Aqueous Solution. An X-ray Diffraction and XAFS Structural Study

Abstract

The yttrium(III) ion is found by means of extended X-ray absorption fine-structure spectroscopy (EXAFS) and large angle X-ray scattering (LAXS) to be hydrated by eight water molecules in aqueous solution. The EXAFS data show a slightly asymmetric distribution of the Y−O bond distances with the centroid of the distribution at 2.368(5) Å. The width of the distribution implies a positional disorder of about 0.1 Å on top of the thermally induced variation in the Y−O bond distances. The aqueous solutions and the solid compound [Y(OH2)8]Cl3·(15-crown-5), in which eight water oxygen atoms form a distorted bicapped trigonal prism around the hydrated yttrium(III) ion, show very similar near-edge and EXAFS spectra. For aqueous solutions the LAXS data give a mean Y−O bond distance of 2.365(5) Å and show the presence of a second hydration sphere consisting of approximately 16 oxygen atoms at a mean Y···O distance of 4.40(4) Å.