Neutron diffraction analysis of barium nitroprusside trihydrate at room temperature
Abstract
The crystal structure of barium nitroprusside trihydrate, Ba[Fe(CN)5NO].3H2O, at room temperature has been refined using neutron diffraction measurements (F(000) = 41.8, Dx = 2.13 g cm−3, μ = 0.6 cm−1 (evaluated), space group Pbcm (57), orthorhombic, Z = 4, a = 7.620(7), b = 19.394(17), and c = 8.631(8) Å, V = 1276(4) Å3). A final R factor of 0.060 was obtained using 1349 observed structure factors. The nitroprusside ion in Ba[Fe(CN)5NO].3H2O presents a distorted octahedral configuration similar to that found in other nitroprusside salts determined by X-ray and neutron diffraction methods. Its polar axis lies in a symmetry plane, which also includes the Ba2+ and the oxygen of one of the water molecules. A positional disorder of the other two water molecules is observed. Two structural phase transitions were found at 130(3) and 112(4) K; they were analyzed from the evolution of selected reflections as a function of temperature in the range between 295 and 77 K.