Ammonium, barium hexacyanoferrate(II) trihydrate: Synthesis, crystal structure, thermal decomposition and spectroscopic study

L. MEDINA CÓRDOBA; G. A. ECHEVERRÍA; O. E. PIRO; M. I. GÓMEZ

JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY

Springer

Lugar: Berlin; Año: 2015 vol. 120 p. 1 - 8

1388-6150

The ammonium, barium hexacyanoferrate(II) trihydrate, Ba(NH4)2[Fe(CN)6].3H2O, has been synthesized for the first time, characterized by TGA, IR and Raman spectroscopy and chemical analysis and its crystal and molecular structure determined by X-ray diffraction methods. The chemical composition was determined assaying Ba(II) through EDTA, ammonia nitrogen with Nessler´s Reagent as indicator and Fe(II) through spectrophotometry with ortho-fenantroline method. The hydration number was estimated by Thermogravimetric Analysis. The compound crystallizes in the trigonal R-3c space group with (in the hexagonal setting) a=b=7.3744(2), c=45.758(2) Å, and Z=6 molecules per unit cell. The structure was solved from 451 reflections with I>2(I) and refined to an agreement R1-factor of 0.016. The ferrocyanide anion has an almost perfect octahedral shape with its Fe(II) ion in a crystallographic special position of point symmetry S6 [d(Fe-C)=1.912(2) Å, d(C-N)=1.153(3) Å]. The barium, ammonium nitrogen and water oxygen atoms are also at lattice special positions with site symmetries D3, C3 and C2, respectively. The thermal decomposition process was also studied using thermogravimetric and differential thermal analysis (TGA-DTA) and the products of decomposition were identified by IR spectroscopy.