PREPARATION AND CRYSTAL-STRUCTURE OF A BASIC ZIRCONIUM MOLYBDATE AND ITS RELATIONSHIP TO ION-EXCHANGE GELS
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abstract
ZrMo2O7(OH)2(H2O)2 was prepared in microcrystalline form by refluxing precipitated zirconium molybdate gels in 1-4M HCl. Macroscopic single crystals have been grown under hydrothermal conditions. In their amorphous, precipitated-gel form the gels are known to function as cation-exchangers. The crystal structure of zirconium molybdate was determined from integrated precession photographs using MoK radiation. Crystal data: tetragonal space group 141cd (No. 110); a = 1145001 A c = 1249001 (25C); {variant}obs = 4001, {variant}calc = 3774g.cm-3. The structure, refined by block diagonal least squares to (conventional) R = 0037, is a three-dimensional network of cross-linked chains built-up of quite regular [ZrO3eq(OH2eqO2ax]-pentagonal bipyramids and distorted cis-MoO4(OH)(H2O-octahedra. The structure is held together primarily by [Zr-O (and OH)-Mo]-bridges; chains of hydrogen bonds involving the oxo-, hydroxo-, and aquo- groups play a secondary role. Intermatomic distances and angles are normal, however, one oxygen atom has unusual coordination geometry; it forms a three-way bridge in a (symmetry-required) planar [ZrOMo2]-moiety. The structure provides a rationale for the thus far observed physical and chemical properties. 1972.