title: Disordering of the [NbOF5]2- complex anions in bis(glycinium) pentafluoridooxidoniobate(V) and bis(beta-alaninium) pentafluoridooxidoniobate(V) dihydrate.
abstract: The title compounds, (C(2)H(6)NO(2))(2)[NbOF(5)], (I), and (C(3)H(8)NO(2))(2)[NbOF(5)].2H(2)O, (II), are built from isolated distorted octahedral [NbOF(5)](2-) complex anions, amino acid cations and water molecules [for (II)]. In the pentafluoridooxidoniobate(V) anions, the Nb and O atoms, and the F atoms in trans positions with respect to the O atoms, are disordered about an inversion centre for both structures. The Nb atoms are shifted from the inversion centres by distances of 0.1455 (1) and 0.1263 (2) A for (I) and (II), respectively. The Nb=O and Nb-F(trans) bond lengths are 1.7952 (3) and 2.0862 (3) A, respectively, for (I), and 1.8037 (7) and 2.0556 (7) A for (II). In the crystal structures, cations and water molecules [for (II)] are linked to the [NbOF(5)](2-) anions via hydrogen bonds. This study demonstrates the possibility of true geometry determination of disordered [NbOF(5)](2-) complex anions in centrosymmetric structures.
authors.affiliation: Institute of Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Prospekt 100-letiya Vladivostoka 159, Vladivostok 690022, Russian Federation. gerasimenko@ich.dvo.ru
authors.forename: A V
authors.initials: AV
authors.lastname: Gerasimenko
authors.forename: M A
authors.initials: MA
authors.lastname: Pushilin
authors.forename: R L
authors.initials: RL
authors.lastname: Davidovich
mesh_terms: D000409:Alanine / Q000138:chemical synthesis / Q000737:chemistry; D000838:Anions / Q000138:chemical synthesis / Q000737:chemistry; D018360:Crystallography, X-Ray; D005998:Glycine / Q000138:chemical synthesis / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000138:chemical synthesis* / Q000737:chemistry*; D015091:beta-Alanine / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D000838:Anions; D010087:Oxides; D009556:Niobium; D015091:beta-Alanine; D000409:Alanine; D005998:Glycine