Infrared and p.m.r. investigations on some complexes of uranyl β-diketonates with methyl-substituted pyridine N-oxides

Several complexes of uranyl β-diketonates with pyridine N-oxides having varying relative degrees of steric hindrance to coordination (2-methyl-3-methyl-,4-methyl-and 2,6-dimethyl-pyridine N-oxide) were isolated by solvent extraction from the system UO22+-β-diketone-pyridine N-oxide in benzene. The β-diketones used were thenoyltrifluoroacetone (tta), benzoyltrifluoroacetone (btfa), acetyl-acetone (acac), benzoylacetone (ba) and dibenzoylmethane (dbm). The analytical data of these complexes lead to their formulation as UO2(β-diketone)2 pyridine N-oxide. Infrared and N.M.R. spectra of these complexes are discussed and interpreted in terms of the substituent constants of the pyridine N-oxide.

Complexes of uranyl β-diketonates with sulphoxides

The proton magnetic resonance spectra of the synergistic complexes of uranyl β-diketonates with dihexyl sulphoxide as the neutral donor give a multiplet consisting of eight lines for the terminal methylene group protons adjacent to the sulphur atom of the sulphoxide and a triplet for the β-methylene protons. This conforms to an ABX2 pattern arising as a result of nonequivalence of the two protons of the terminal methylene group as a result of steric hindrance to free rotation about the C-S bond. The presence of such restricted rotation has been adduced as evidence for a direct donor-metal bond.