Crystal structures of potassium, ammonium, rubidium, and cesium tetrafluoborates

Abstract

The crystal structures of potassium, ammonium, and rubidium tetrafluoborates have been redetermined. The structure of cesium tetrafluoborate has also been established. These 4 compounds are isomorphous and show orthorhombic symmetry, space group Pbnm. Atomic parameters have been obtained from a block diagonal least squares refinement using anisotropic temperature parameters. The final agreement residuals for observed reflections were KBF4, R = 0.072; NH4BF4, R = 0.075; RbBF4, R = 0.064; and CsBF4, R = 0.051.There are significant differences between some of the B-F bond distances in the [BF4]-ions. The shortest N---(H)F distance in NH4BF4 is 2.914 A (estimated standard deviation 0.005 A) which is long for a hydrogen bond. The positions of the hydrogen atoms in the NH4+ ion could not be established.

Synthesis of Zinc Hydroxyfluoride Nanofibers through an Ionic Liquid Assisted Microwave Irradiation Method

“…The formation of the Zn(OH)F nanofibers may be possibly explained by a hydrogen bonding π-π stacking mechanism. As shown in Scheme 1b, the F-F distance in the BF 4 -anion is about 2.28 Å, [12] which is close to the distance (ca. 2.1 Å) [3] between coplanar anions placed at each Zn(OH) 3 F 3 octahedron.…”

Comparison of the crystal structures of alkaline (M = Li,Na,K,Rb,Cs) and pseudo-alkaline (M = NO,NH4) tetrachloroaluminates, MAlCl4

“…In contrast to other tetrahedral anion salts such as MBF 4 (Clark & Lynton, 1969;Brunton, 1969) and MCIO 4 (Johansson & Lindqvist, 1977;Choi, Prask & Prince, 1976), the K + salt does not crystallize in the same space group as the Rb +, Cs + and NH + salts (Table 1). The KAICI 4 lattice symmetry of P2~ is close to P2~/m but, as can be seen from its Raman spectrum (Rubbens, Barbier, Mairesse, Wallart & Wignacourt, 1977), the crystal behaves like an apparent orthorhombic crystal in P2~2~2~, the space group of NaA1CI 4.…”

Structure of 1,3-xylyl-(18-crown-5)–ammonium catecholborate (1/1)

“…Interestingly, the ammonium cation forms hydrogen bonds preferentially with the O atoms of the crown ether in spite of the fact that the catecholborate anion is negatively charged and carries four O atoms that are eminently suited to form hydrogen bonds. By way of comparison, ammonium tetrafluoroborate crystallizes as a three-dimensional structure with each H atom of the ammonium cation hydrogen bonded, albeit weakly (Pendred & Richards, 1955), to an F atom of a neighbouring tetrafluoroborate anion (Clark & Lynton, 1969; Van Rensburg & Boeyens, 1972;Stromme, 1974 LSCELD (Davis, 1969 …”