NEUTRON AND X-RAY SINGLE-CRYSTAL STRUCTURE DETERMINATION OF BE(IO3)(2)CENTER-DOT-4H(2)O

The crystal structure of Be(IO3)(2) . 4 H2O has been determined by bot h neutron and X-ray single-crystal studies (Pccn, Z = 4, a = 1581.0(6) pm, b = 650.66(10) pm and c = 877.5(2) pm, R = 4.20% and 2.50%) on th e basis of 402 and 1063 reflections, respectively, and synchrotron X-r ay powder diffraction. The layered structure is built up of tetrahedra l Be(H2O)(4)(2+) units linked to adjacent iodate ions by hydrogen bond s. The shortest interionic I...I and I...O distances are with 360.1 pm and 276.8 pm unusually small, the intraionic bond lengths resemble th ose of other iodate hydrates. The four crystallographically different hydrogen bonds (H-r...O: 159.6 pm, 166.0 pm, 167.0 pm and 178.4 pm), w hich are the strongest bonds known so far of salt hydrates, as also es tablished by the wavenumbers of the uncoupled OD stretching modes, are discussed in connection with the bond valences of the intramolecular OH bonds and the great synergetic effect of Be2+ ions.