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

Abstract

Abstract The ammonium, barium hexacyanoferrate(II) trihydrate, Ba(NH4)2[Fe(CN)6]·3H2O, has been synthesized for the first time, was characterized by thermogravimetric and differential thermal analysis (TG-DTA), infrared (IR) and Raman spectroscopy and chemical analysis, and its crystal and molecular structures were determined by X-ray diffraction methods. The chemical composition was determined by assaying Ba(II) with EDTA, ammonia nitrogen with Nessler's reagent as indicator and Fe(II) using spectrophotometry with ortho-phenanthroline method. The hydration number was estimated by thermogravimetric analysis. The compound crystallizes in the trigonal R-3c space group. 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 TG-DTA, and the products of decomposition were identified by IR spectroscopy. It proposes a mechanism of decomposition.