Neutron and X-ray single-crystal structure determination of Be(IO3)2 · 4H2O

The crystal structure of Be(IO3)2 · 4H2O has been determined by both 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 the basis of 402 and 1063 reflections, respectively, and synchrotron X-ray powder diffraction. The layered structure is built up of tetrahedral Be(H2O)4 2+ units linked to adjacent iodate ions by hydrogen bonds. 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 those of other iodate hydrates. The four crystallographically different hydrogen bonds (rH…o: 159.6 pm, 166.0 pm, 167.0 pm and 178.4 pm), which are the strongest bonds known so far of salt hydrates, as also established 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.