CRYSTAL-STRUCTURE OF THE MONOCLINIC POLYMORPH [CO(NH3)(5)NO2]I-2

X-ray diffraction study of [Co(NH3)(5)NO2]I-2 needle crystals war carr ied out at 293 and 150 K an automatic diffractometer, MoKalpha radiati on, lambda = 0.71073 Angstrom space group C2/m, Z = 8. The unit cell p arameters are a = 24.047(5), b = 7.648(2), c = 17.599(4) Angstrom, bet a = 132.48(3)degrees, V-cell = 2387.0910 Angstrom(3), d(calc) = 2.479 g/cm(3) at 293 K and a = 23.763(5) b = 7.577(2), c = 17.551(4) Angstro m, beta = 132.12(3)degrees, V-cell = 2343.9(1) Angstrom(3), d(calc)= 2 .516 g/cm(3) at 150 K, respectively. The R(F) values are 11.93% (at 29 3 K) and 12.30% (at 150 K) for 2032 and 2948 observed reflections, res pectively. The structure is of the ionic-island type. [Co(NH3)(5)NO2]( 2+) complex cations are clustered in [Co(NH3)(5)NO2](4) ''supercations ,'' which are linked by N-(NH3)...O-(NO2) hydrogen bonds and have 2/m symmetry. A shortening of the distances between certain I ions is indi cative of their noticeable interaction. Short contacts also exist betw een the iodine anions and the ammonia molecules of the complex cations , suggesting the possible formation of NH3...I hydrogen bonds. The str ucture investigated is compared with the structures of the orthorhombi c and tetragonal modifications of [Co(NH3)(5)NO2]I-2, along with the s tructures of alpha-Ag1 and transition-metal hexaammoniate polyiodides.