| Abstract: | Crystal Structures and Hydrogen Bonding for β-Be(OH)2 and ϵ-Zn(OH)2 Crystals of β-Be(OH)2 sufficient for x-ray structure determination were grown from a saturated hot solution of freshly prepared Be(OH)2 in NaOH by slowly cooling down and in the case of ϵ-Zn(OH)2 by electrochemical oxidation of zinc in a NaOH/NH3 solution. The structures of the isotypic compounds were determined including the H-positions: β-Be(OH)2: P212121, Z = 4, a = 4.530(2) Å, b = 4.621(2) Å, c = 7.048(2) Å N(F > 3σ F ) = 432, N(parameters) = 36, R/Rw = 0.044/0.052 ϵ-Zn(OH)2: P212121, Z = 4, a = 4.905(3) Å, b = 5.143(4) Å, c = 8.473(2) Å N(F > 3σ F ) = 1107, N(parameters) = 36, R/Rw = 0.025/0.027For neutron diffraction experiments microcrystalline β-Be(OD)2 was prepared. With time-of-flight data the D positions were determined giving d(O–D) = 0.954(4) Å. The structures are closely related to that of β-cristobalite: As in SiO2 a quarter of tetrahedral interstices in a distorted cubic close packed arrangement of O is regularily occupied by the metal atoms. The filled O tetrahedra are twisted against one another in such a way, that O–H…O–H hydrogen bonds are favoured which are surprisingly stronger in the zinc than in the beryllium compound. |
