Figure 1.

Molecular structures of all studied compounds derived from the X-ray diffraction data collected in complete darkness. Atomic thermal motion is represented as ellipsoids at the 50% probability level, selected hydrogen atoms are omitted for clarity, and the disorder is shown as a semitransparent fragment. For the Ni-2a complex, only the nitro isomer is labeled for clarity; for the Ni-2b complex, the atom labeling is shown for the low-temperature triclinic structure (the labeling of the high-temperature monoclinic structure follows that of the molecule A).