The proton nmr isotropic shifts of pyridine type ligands coordinated to paramagnetic nickel(II) and cobalt(II) acetylacetonate are reported, and the mechanisms of unpaired electron spin delocalization in these complexes are discussed. It is found that a σ-delocalization mechanism is in dominant, but the π-contribution can not be rule out. The calculations of the geometric factor for Co(II) complexes are done. It is used in the ratio method to separate the contribution of pseudo-contact shift from isotropic shift for Co(II) complexes. The effect of pseudoaromatic chelate ring on contact shift is not so large as previous reported.
關聯:
中國化學會會誌=Journal of the Chinese Chemical Society 25(4)，頁185-194
