Metal (Ca, Ba, Sr, Pb) heptafluorotantalates(V): Synthesis, Raman spectra and crystal structures

• Published in: Solid state sciences 2007, Vol.9 (1), p.88-94
• Main Authors: Bunič, Tina, Tramšek, Melita, Goreshnik, Evgeny, Žemva, Boris
• Format: Article
• Language: English
• Subjects: Barium; Calcium; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Crystal structure; Exact sciences and technology; General and physical chemistry; Heptafluorotantalates(V); Lead; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Physics; Strontium; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Theory of reactions, general kinetics; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Twinning
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2006.11.017

MTaF 7 (M = Ca, Sr, Ba, Pb) were prepared by the reaction of MF 2 + Ta + F 2 (Ca, Sr, Ba) or MF 2 + TaF 5 in anhydrous HF. CaTaF 7 crystallizes in a monoclinic P2 1/ a space group, a = 9.793(3) Å, b = 11.608(3) Å, c = 13.359(4) Å, β = 90.539(13)°, V = 1518.5(7) Å 3. All Ta atoms possess distorted pentagonal-bipyramidal environment with Ta–F distances of 1.878(14)–2.044(13) Å. Three crystallographically independent Ca atoms have coordination number 8. Ca–F distances lie in the range of 2.239(16)–2.836(17) Å. Each Ca 2+ and TaF 7 2− moiety is bonded to 6 counter-ions. BaTaF 7 crystallizes in a cubic system, space group P a 3 ¯ , a = 9.9009(3)Å, V = 970.56(5) Å 3. Coordination sphere around Ta atom is mono-capped trigonal prism with a Ta–F distance of 1.916(5)–2.004(5) Å. Two crystallographically independent barium atoms have different coordination numbers: for Ba1 C.N. is 12 with Ba1–F distances of 6 × 2.761(5) Å and 6 × 2.858(5) Å, for Ba2 C.N. is 14 with Ba2–F bond lengths 6 × 2.718(5), 2 × 2.814(8) and 6 × 3.236(5) Å. Ba 2+ and TaF 7 2− moieties are bonded to 8 neighbors. Isostructural PbTaF 7 and SrTaF 7 appear to be monoclinic, space group P2 1/ m, a = 4.8657(11) Å, b = 7.2298(16) Å, c = 6.7370(16) Å, β = 93.932(13)°, V = 236.44(9) Å 3 for PbTaF 7, and a = 4.875(3) Å, b = 7.196(4) Å, c = 6.7218(13) Å, β = 94.265(10), V = 235.2(2) Å for SrTaF 7. Tantalum coordination polyhedron may be described as a distorted mono-capped trigonal prism with the capping atom located on one of the rectangular faces with Ta–F distances of 1.868(3)–1.982(3) Å (PbTaF 7) and 1.908(16)–2.019(12) Å (SrTaF 7). Lead (or strontium) atoms are 9-coordinated and may be viewed as strongly distorted tri-capped trigonal prism, Pb–F 2.438(4)–2.669(3) Å, Sr–F 2.501(19)–2.860(19) Å. Each cation is connected to 8 anions. [Display omitted]