Crystal structure of [Co(NH3)5NO2]C2O4. Analysis of specific contacts and structural effects hindering inner-spheric nitro-nitrito isomerization

The structure of [Co(NH₃)₅NO₂]C₂O₄ is solved and refined (space group Immm, a=7.428(2), b=9.790(3), c=6.568(1) Å, V=477.6(2) ų, Z=2; R₁=0.0177, wR₂=0.0279 for F²>4σ(F²); R₁=0.1177, wR₂=0.0643 for all data; residual electron density from 0.125 to ?0.140 e/ų). Specific contacts in the structure are analyzed. Crystal chemical interpretation is suggested to explain the occurrence of photodecomposition rather than photochemical bond isomerization under the action of light in cobalt(III) nitropentammoniate oxalate crystals, in contrast to all previously investigated cobalt(III) nitropentammoniates.