The crystal structure of Na₂[B₄O₆(OH)₂]

Abstract

The crystal structure of the synthetic compound Na20. 2B203.H20, orthorhombic space group Pbea, a = 8.540 (4), b = 10.263, c = 14.547 (6) A, was determined from single-crystal X-ray diffractometer data. The unit cell contains eight formula units. The crystal structure was solved by means of direct methods and refined by least-squares calculations to an R index of 0.050. Present in the structure are B-O chains, with repeat unit [B406(OH)2] 2-, which are the product of polymerization, by elimination of water, of the isolated polyanions [B405(OH)4] 2-found in the structure of some sodium or potassium borates, e.g. borax and tincalconite. Na(1) and Na(2) are coordinated by six and seven O atoms respectively. The Na-O irregular polyhedra are connected to each other in various ways. Connexions between B-O chains are provided by Na polyhedra and by the hydrogen-bonding system to form a three-dimensional network. The crystal-chemical formula is Na2[BaO6(OH)2].

Potassium Strontium Tetraborate Decahydrate and Ammonium Calcium Tetraborate Octahydrate

“…The crystal structures of tetraborate compounds have been extensively explored in recent years. The structures the following monovalent-ion tetraborates have been solved: NI-h (Janda, Heller & Pickardt, 1981), Na (Menchetti & Sabelli, 1978;Powell, Gaines, Zerella & Smith, 1991), K (Marezio, Plettinger & Zachariasen, 1963) and T1 (Touboul, Bois & Amoussou, 1983). Only the structures of tetraborates containing Mg (Wan & Ghose, 1977) and Mn (Berzinja, Ozols & Ievinsh, 1975) as divalent ions and [K,Ca] (Solans, Font-Altaba, Solans & Dombnech, 1982) and [Rb,Sr] (Ivchenko & Kurkutova, 1975) as mixed monovalent and divalent ions have been solved.…”