1H, 13C, 14N, 19F Nuclear Magnetic Resonance Contact Shifts and Electron Spin Distribution in Aniline and Fluoroanilines – Ni(II) Acetylacetonate Complexes

Abstract

The contact shifts of 1H, 13C, 14N, and 19F in chloroform solutions of Ni(II) acetylacetonate -aniline and fluoraniline complexes have been studied by high resolution n.m.r. The unpaired electron spin distribution in these ligands is compared to that calculated by the INDO method for the corresponding aniline cation radicals. The ratio of the hyperfine coupling constants aNHH/aN suggests that in these aniline complexes the [Formula: see text] fragment is pyramidal with an angle of 13–15° between the perpendicular of the C—N bond and the axis of the p like orbital centered on nitrogen. The electron spin distribution between the NH2 group and the phenyl ring may be partially accounted for by assuming an internal rotation about the C—N bond. The 13C relaxation indicates a N—Ni distance of the order of 2 Å for aniline and 2 fluoraniline complexes and an electron spin-lattice relaxation time of ∼5 × 10−10 s at 300 °K.