PRESSURE-INDUCED LATTICE DISTORTION IN SOME CO(III)-AMMINE COMPLEXES, [CO(NH3)5NO2]XY (XY=CL2, BR2, CL(NO3))

Lattice parameters were measured at pressures up to 4 GPa (40 kbar) for [Co(NH3)5NO2]Xy (XY=Cl2, Br2, Cl(NO3)) by X-ray powder diffraction using a Diamond Anvil Cell (DAC) technique. Continuous anisotropic lattice distortion with increasing pressure was observed. Strain tensors were calculated at different pressures, and the orientation of strain ellipsoids with respect to the crystallographic axes and the directions of various bonds in the structures was considered. Pressure induced lattice distortion was compared with lattice distortion in the course of homogeneous nitro-nitrito linkage isomerization in the crystals. The data on the orientation of Co-NO2 bonds with respect to the directions of main compression in the crystals correlate with previously obtained data on pressure induced frequency shifts in the solid state IR-absorption spectra in the same series.