Dioxouranium(VI) complexes of aliphatic (mono- and di-) hydrazone-oximes

Summary Uranyl acetate dihydrate reacts with several hydrazone-oximes, derived from aliphatic (mon-annd di-) hydrazides and 2,3-butanedione monoxime in the absence of NaOAc, to form complexes of general formulae [UO₂(HL)₂] and [UO₂(HL)₂SZ] (where H₂L=aliphatic acid monohydrazone-oximes; S=EtOH and Z=H₂O). With aliphatic acid dihydrazone and monomaleoyl-hydrazone-oximes, different complexes have been synthesized in 50% EtOH and in the absence of NaOAc. The products have been characterized by elemental analyses, molar conductivities, spectral (u.v., i.r., n.m.r.), pH, conductometric titrations, molecular weights and magnetic measurements. I.r. spectral data indicate that the aliphatic hydrazone-oximes, except monomaleoyl-hydrazone-oxime, behave in a similar way to tridentate ligandsvia the azomethine nitrogen and the NOH groups, with replacement of a hydrogen atom from the latter group. On the other hand, malonyl dihydrazone- and adipoyldihydrazone-oximes coordinate in a bi-, and tridentate manner, respectively, towards one uranyl ion, while monomaleoyl- and oxaloyldihydrazone-oximes behave in a penta-and hexadentate fashion, respectively, towards two uranyl ions. Elemental analyses, molecular weight measurements as well as spectral data confirm the existence of a binuclear complex for monomaleoyl- and oxaloyldihydrazone-oximes, whereas a monomer for the rest. Finally, the role of solvent, absence of NaOAc and the type of ligand on the structure of the complexes are discussed.