The crystal and molecular structures of [Co(NH 3) 6][CuCl 5] as determined from single crystal X-ray and neutron diffraction data

Abstract

The crystal structure of the title compound was determined at room temperature ( ca. 21°C) using single crystal X-ray and neutron diffraction data. The substance crystallizes in the cubic space group O h 8-Fd3c in a unit cell whose edge is a = 21.992(3)Å. The X-ray data were refined to R(F 0) = 0.026 and R w(F 0) = 0.027, while the neutron data refined to R(F 0) = 0.055. The two sets of coordinates obtained agree remarkably well even for the hydrogen atoms but, since the neutron results are more reliable for the hydrogen atom positions, our discussion is based on these. The Co-N and <N-H > distances are, respectively, 1.968(2)Å and 0.953(5)Å. The most important result, namely the Cu-Cl(axial)Cu-Cl(equat.) ratio, is 0.955; the individual values of these quantities being Cu-Cl(ax) = 2.301 and Cu-Cl(equat.) = 2.409. Thus, the CuCl 5 3− anion is axially compressed by a substantial amount and, in this respect, resembles its octahedral CuF 6 4− relative.