Synthesis, crystal structure and topological features of microporous 'anti-zeolite' Yb-3(BO3)(OH)(6)center dot 2.1 H2O, a new cubic borate with isolated BO3 groups

摘要

A new cubic borate, Yb-3[BO3](OH)(6)center dot 2.1H(2)O was synthesized in a multi-component hydrothermal system Yb-2(CO3)(3):B2O3: P2O5 = 5 : 2: 1 (T = 280 degrees C; P = 90-100 atm; pH = 3). The crystal structure was studied using single crystal X-ray analysis. The structure has been refined in the space group 1432, possesses the unit cell parameter a = 12.2808(15) angstrom. A microporous positively charged framework is formed by predominant Yb cations coordinated by O-2(-), OH- as a tetragonal antiprism, which are linked together via common edges and vertices. The extra framework BO3 triangles center narrow channels, directed along 3-fold axis, are perpendicular to them and clamped between large Yb polyhedra. The large cavities with the effective cavity width 7.7 angstrom are filled by disordered water molecules. The crystal chemical formula could be written as (Z = 8): [(BO3)(H2O)(2.1)] [Yb-3(OH)(6)]. A topological analysis was performed using the ToposPro software. The framework is characterized by the following tile sequence: [3(4)](6)[3(24).4(6).6(8)] the calculated structural complexity parameters are: v = 48 atoms, I-G = 1.500 bits/atom, and I-G,(total) = 72.000 bits/unit cell; the framework density is 12.96 Yb/1000 angstrom(3). The Yb-borate is similar to the tetragonal compounds with the general formula ABa(12)(BO3)(7)F-4 (A = Li, Na) and LixNa1-xBa12(BO3)(7)F-4, which are characterized by co-called "anti-zeolite" frameworks, formed by Ba(2+ )cations. The excess of water in the structure of the new borate compound Yb-3[BO3](OH)(6)center dot 2.1H(2)O is determined by its zeolitic nature and by hydrothermal growth conditions.