Structural characterization of nitro-substituted phenoxyiminato nickel complexes; inter-molecular π–π interactions in the solid states and effect of the electron drawing groups on catalytic activity

Three phenoxyiminato nickel complexes [(L)Ni(PPh3)(Ph)] have been prepared by the introduction of the electron drawing nitro substitutes on ortho or para-position of phenoxy and characterized by X-ray crystallography. Experimental and theory calculation suggested that the ortho and para nitro groups may be equally responsible for the small net charge on the central metal atoms because the interplanar angles between o-nitro planes and aromatic rings (28.7–37.3°) are much higher than those between p-nitro planes and aromatic rings (8.2–13.8°). In the solid states of these nickel complexes there exist the short inter-molecular π–π stacking interactions with the distances of 3.5828 Å (ortho-nitro), 3.5844 Å (para-nitro), and 3.0929 Å (ortho- and para-nitro) between two neighboring nitro-phenyl moieties.