Dioxouranium(VI) complexes with 2,6-acetylpyridinebenzoylhydrazones and -semicarbazones

• Published in: Inorganica Chimica Acta Vol. 357; no. 15; pp. 4405 - 4412
• Main Authors: Gatto, C.C., Lang, E. Schulz, Jagst, A., Abram, U.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2004
• Subjects: Actinides; Benzoylhydrazones; Semicarbazones; Structure analysis; Uranium; Uranium; Actinides; Semicarbazones; Structure analysis; Benzoylhydrazones
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2004.07.011

Symmetric and asymmetric benzoylhydrazones and semicarbazones derived from 2,6-diacetylpyridine react with common dioxouranium(VI) compounds to form air-stable complexes. The neutral compounds contain doubly deprotonated ligands and possess uranium atoms with distorted pentagonal-bipyramidal coordination spheres. The equatorial coordination spheres of the metal atoms can be extended by the addition of a monodentate ligand such as pyridine or DMSO. Benzoylhydrazones and semicarbazones derived from 2,6-diacetylpyridine react with common dioxouranium(VI) compounds such as uranyl nitrate or [NBu 4] 2[UO 2Cl 4] to form air-stable complexes. 2,6-Diacetylpyridinebis(benzoylhydrazone) (H 2L 1), 2,6-diacetylpyridinebis(N4-phenylsemicarbazone) (H 2L 2) and the asymmetric proligand 2,6-diacetylpyridine(benzoylhydrazone)(N4-phenylsemicarbazone) (H 2L 3) give yellow products of the composition [UO 2(L)]. The neutral compounds contain doubly deprotonated ligands and possess uranium atoms with distorted pentagonal-bipyramidal coordination spheres. The equatorial coordination spheres of the metal atoms can be extended by the addition of a monodentate ligand such as pyridine or DMSO. The uranium atoms in the resulting complexes have hexagonal-bipyramidal coordination environments with the oxo ligands in axial positions. X-ray diffraction studies on [UO 2(L 1)(DMSO)], [UO 2(L 2)], [UO 2(L 2)(DMSO)] and [UO 2(L 3)] show relatively short U–O bonds to the benzoylic oxygen atoms between 2.273(6) and 2.368(5) Å. This suggests a preference of these donor sites of the ligands over their imino and amine functionalities (U–N bond lengths: 2.502(7)–2.671(7) Å). The addition of a sixth ligand to the equatorial coordination sphere results in a lengthening of the metal–pyridine bonds.