Reactivity of uranyl ion with quinquedentate chelating hydrazine derivatives. Part 3. 2,6-Diacetylpyridine (2′-pyridylhydrazone)(4″-toluoylhydrazone)

Abstract

The new title ligand HH* dappt reacts with [UO₂][NO₃]₂.6H₂O in ethanol to give [UO₂(Hdappt)][NO₃](1) in which the ligand is co-ordinated in its semienolized monodeprotonated form, with formation of four fused five-membered rings around the uranyl moiety. The related complex [UO₂(Hdappt)][BPh₄](2) has been synthesized by the action of an excess of Na[Bph₄] on (1). Compounds (1) and (2) when treated with a number of non-hydroxylated bases are transformed to deep violet [UO₂(dappt)](3) which, owing to the presence of only one reactive U–N covalent bond, reacts with hydroxylated species such as benzoic and acetic acid to give monomeric products in which the equatorial co-ordination number is increased from five to six; [UO₂(Hdappt)(O₂CC₆H₅)](4) and [UO₂(Hdappt)(O₂CCH₃)](5), in both of which the carboxylate group is unidentate, have been isolated. Both the ligand and complexes have been characterized by physicochemical measurements.