DISTORTION OF CRYSTAL-STRUCTURES OF SOME CO-III AMMINE COMPLEXES .2. DISTORTION OF CRYSTAL-STRUCTURES OF [CO(NH3)(5)NO2]X-2 (X=CL, BR) ON COOLING

For two solid complexes, [Co(NH3)(5)NO2]X-2 (X = Cl-, Br-), pentaammin enitrocobalt(III) dichloride/dibromide, the anisotropy of structural d istortion on cooling the samples from 290 to 150 K was studied by vari able-temperature single-crystal X-ray diffraction. The changes in latt ice parameters were used to calculate the strain tensors and to scan l inear strain in various crystallographic directions. The changes in di fferent intra- and intermolecular distances in the structure were foll owed. Lattice strain on cooling was compared with lattice strain in th e same structures under high hydrostatic pressure and with structural distortion in the course of homogeneous nitro-nitrito linkage isomeriz ation. The effect of isomorphous substitution (Br- for Cl-) with respe ct to structural strain was discussed. Structural strain in the monocl inic chloride and bromide was compared also with the previously obtain ed data [Boldyreva, Kivikoski & Howard (1997). Acta Cryst. B53, 394-40 4] on strain in the orthorhombic structure of another compound of the same Co-III nitropentaammine series, [Co(NH3)(3)NO2]Cl(NO3).