Abstract
Proton magnetic resonance spectra of a series of alkyl(oxinato)tin(IV) complexes, alkyl(oxinato)thallium(III), dimethylbis(oxinato)lead(IV), 8‐methoxyquinoline, 2‐methyl‐8‐hydroxyquinoline and 8‐hydroxyquinoline were studied. The indirect spin‐spin coupling constants J~23~, J~34~ and J~24~ of the oxinato ligand in the alkyl(oxinato)tin(IV) complexes and of 8‐methoxyquinoline were found to be 4.4 ± 0.2, 8.3 ± 0.2 and 1.7 ± 0.2 Hz, respectively. When the interaction between tin and nitrogen in the oxinato ligand is not strong as in trialkyl(oxinato)tin(IV), the resonance of the 2‐proton of the ligand shifts to high magnetic field relative to that of 8‐methoxyquinoline, but in the case of the strong interaction, as in dimethyl(oxinato)halogenotin(IV), the resonance is shifted to low magnetic field. The 4‐proton signals, however, shift monotonously to low magnetic field with increasing interaction. The behaviour of the 2‐proton signals was explained by a paramagnetic anisotropic effect of a nitrogen lone pair of the oxinato ligand and an intramolecular electric field effect and that of the 4‐proton by the latter effect. By comparing the change of the δ‐values of the 2‐, 3‐ and 4‐protons of the alkyl(oxinato)tin(IV) complexes and those of 8‐hydroxyquinoline by altering the solvents, from methylene chloride to benzene, it was found that the electron density around the 2‐carbon is reduced in the complexes compared with that of 8‐hydroxyquinoline.