Potassium heptafluoroniobate

Crystal structure
__ K +      __ Nb 5+      __ F -
General
Surname	Potassium heptafluoroniobate
other names	Potassium niobium heptafluoride Potassium Heptafluoridoniobate ( IUPAC )
Ratio formula	K 2 [NbF 7 ]
Brief description	white solid
External identifiers / databases
CAS number 16924-03-1 EC number 240-987-7 ECHA InfoCard 100.037.246 PubChem 44890706 Wikidata Q15069049
properties
Molar mass	304.09 g mol −1
Physical state	firmly
density	3.19 g cm −3
Melting point	733 ° C
solubility	soluble in water (80 g l −1 at 18 ° C)
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 315-319-335 P: 261-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium heptafluoroniobate is an inorganic chemical compound of potassium from the group of potassium fluorine complexes .

Extraction and presentation

Potassium heptafluoroniobate can be obtained by reacting niobium (V) oxide with hydrofluoric acid and potassium hydrogen difluoride .

${\displaystyle \mathrm {Nb_{2}O_{5}+6\ HF+4\ KHF_{2}\longrightarrow 2\ K_{2}[NbF_{7}]+5\ H_{2}O} }$

properties

Potassium heptafluoroniobate is a hygroscopic white solid that is soluble in water and comes in the form of small, very shiny needles. [NbF ₇ ] ²⁻ easily hydrolyzes to [NbOF ₅ ] ²⁻ . Potassium heptafluoroniobate has a monoclinic crystal structure with the space group P 2 ₁ / c (space group no. 14) and the lattice parameters a = 5.846 Å , b = 12.69 Å, c = 8.515 Å and β = 90.0 °.

use

Potassium heptafluoroniobate is used for the electrochemical synthesis of niobium diboride NbB ₂ . It also serves as an intermediate for the production of niobium from Nioberzen as niobite by electrolysis at about 800 ° C. K ₂ [NbF ₇ ] doped with Mn ⁴⁺ has been proposed as a luminescent material for warm white LEDs, since it exhibits intense narrow-band red luminescence under UV or blue excitation.

Individual evidence

1. ↑ ^{a b c d} data sheet potassium heptafluoroniobate from AlfaAesar, accessed on October 14, 2013 ( PDF )(JavaScript required) .
2. ↑ Anatoly Agulyansky: Chemistry of Tantalum and Niobium Fluoride Compounds . Elsevier, 2004, ISBN 0-08-052902-X , pp. 64 ( limited preview in Google Book search).
3. ↑ ^{a b c} Georg Brauer , with the assistance of Marianne Baudler a . a. (Ed.): Handbook of Preparative Inorganic Chemistry . 3rd, revised edition. tape I . Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , pp. 262 .
4. ↑ ^{a b c} data sheet Potassium heptafluoroniobate (V), 98% from Sigma-Aldrich , accessed on October 14, 2013 ( PDF ).
5. ↑ GM Brown, LA Walker; Refinement of the Structure of Potassium Heptafluoroniobate, K ₂ NbF ₇ , from Neutron-Diffraction Data. In: Acta Crystallographica , 20, 1966, pp. 220-229, doi: 10.1107 / S0365110X66000458 .
6. ^ Hans Günther Hirschberg: Handbook of process engineering and plant construction: chemistry, technology, economic efficiency . Springer DE, 1999, ISBN 3-642-58357-1 , p. 284 ( limited preview in Google Book search).
7. ↑ Thomas Jansen, Florian Baur, Thomas Jüstel: Red emitting K2NbF7: Mn4 + and K2TaF7: Mn4 + for warm-white LED applications . In: Journal of Luminescence . tape 192 , p. 644–652 , doi : 10.1016 / j.jlumin.2017.07.061 ( elsevier.com [accessed October 12, 2017]).