Synthetic and structural studies of piperidine carboxamide uranyl ion complexes

New piperidine based ligands of the type [C5H10NCONR2] (where R = CH3 (L1), C2H5 (L2) and iC3H7 (L3)) have been prepared and characterized. The complex chemistry of these ligands with uranyl chloride, bromide, nitrate and β-diketonates has been studied using IR and NMR spectroscopic methods. Crystal structures for the complexes [UO2Cl2(L3)2] (1), [UO2Br2(L3)2] (2) [UO2(NO3)2(L3)2] (5) and [UO2(C4H3SCOCHCOCF3)2(L3)] (8) have been determined by the X-ray diffraction method. The structures of 1 and 2 show that the uranyl ion is surrounded by two of the ligands and two halogen atoms in an octahedral geometry. The structure of 5 shows that the uranyl group is surrounded by two nitrate groups and two ligands in a hexagonal bipyramidal geometry. The structure of 8 shows that the uranyl group is surrounded by two β-diketonates and one ligand in a pentagonal bipyramidal geometry. The structures show that the carboxamide ligands are strongly bonded to the uranyl group, showing a near linear geometry for the U–O–C bond (angle 150–159°). The prepared chloro and bromo compounds are air and moisture stable and show good solubility in normal organic solvents.

The complex chemistry of piperidine based amide ligands with uranyl chloride, bromide, nitrate and β-diketonates shows that the ligands bond through the amido oxygen atom to the uranyl group. The structures of the uranyl halides, nitrate and bis(β-diketonates) show octahedral, hexagonal bipyramidal and pentagonal bipyramidal geometries around the uranyl group respectively. The structures further show that the carboxamide ligands are strongly bonded to the uranyl group by showing a near linear geometry for the U–O–C bond angles (150–159°).Figure optionsDownload as PowerPoint slide