Stable Anilinyl Radicals Coordinated to Nickel: X-ray Crystal Structure and Characterization.

Two anilinosalen and a mixed phenol-anilinosalen ligands involving sterically hindered anilines moieties were synthesized. Their nickel(II) complexes 1, 2, and 3 were prepd. and characterized. They could be readily one-electron oxidized (E1/2=-0.30, -0.26 and 0.10 V vs. Fc+/Fc, resp.) into anilinyl radicals species [1]+, [2]+, and [3]+, resp. The radical complexes are extremely stable and were isolated as single crystals. X-ray crystallog. structures reveal that the changes in bond length resulting from oxidn. do not exceed 0.02 {\AA} within the ligand framework in the sym. [1]+ and [2]+. No quinoid bond pattern was present. In contrast, larger structural rearrangements were evidenced for the unsym. [3]+, with shortening of one Cortho-Cmeta bond. Radical species [1]+ and [2]+ exhibit a strong absorption band at ∼6000 cm-1 (class III mixed valence compds.). This band is significantly less intense than [3]+, consistent with a rather localized anilinyl radical character, and thus a classification of this species as class II mixed-valence compd. Magnetic and electronic properties, as well as structural parameters, have been computed by DFT methods. [on SciFinder(R)]


Soumis le 12 avril 2018