Low temperature crystal structure of [Cr(NH 3) 6](BF 4) 3

• Published in: Journal of alloys and compounds 2007-09, Vol.442 (1), p.80-82
• Main Authors: Górska, N., Hetmańczyk, Ł., Łasocha, W., Mikuli, E.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystal structure; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Inorganic compounds; Phase transition; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Transition metal coordination compound; X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2006.12.151

The crystal structure of [Cr(NH 3) 6](BF 4) 3 at 150 K was determined from X-ray powder diffraction data. Rietveld method was applied to initial starting model obtained from FOX Monte Carlo computer program. The low temperature phase of the titled compound crystallises in orthorhombic crystal system in space group Pnma (no. 62) with lattice constant a = 15.953(2) Å, b = 11.293(1) Å, c = 8.025(1) Å and four molecules per unit cell. Complex [Cr(NH 3) 6] 3+ cation has octahedral and BF 4 − anion tetrahedral symmetry. Differences between the structures of the high (cubic, F m 3 ¯ m ) and the low (orthorhombic, Pnma) temperature phases indicate an order-disorder character of the structural phase transition at T C = 238 K.