A structural study on uranyl (VI) nitrate complexes with cyclic amides:: N-n-butyl-2pyrrolidone, N-cyclohexylmethyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidone

Structural analyses Of UO2(NO3)(2)L-2 [L = N-n-butyl-2-pyrrolidone (NBP), N-cyclohexylmethyl-2-pyrrolidone (NCMeP), and 1,3dimethyl-2-imidazolidone (DMI)] have been carried out using X-ray diffraction method. These uranyl complexes were found to have a hexagonal bipyramidal structure. The bond distances (angstrom) of U=O and U-O(ligand), and bond angles (degrees) of U-O-C(carbonyl) are determined as follows: 1.774(2), 2.374(2), and 137.6(2) for UO2(NO3)(2)(NBP)(2); 1.770(l), 2.383(2), and 135.3(l) for UO2(NO3)(2)(NCMeP)(2); 1.771(2), 2.361(2), and 143.3(2) for UO2(NO3)(2)(DMI)(2)- In uranyl nitrate complexes with cyclic amides such as 2-pyrrolidone, urea, and caprolactam derivatives, a linear correlation was found to hold between U-O(ligand) bond distances and U O-C(carbonyl) bond angles. Vibrational frequencies Of UO2(NO3)(2)L-2 have also been measured by IR and Raman spectrophotometers. Using relationships between vibrational frequencies of O=U=O bonds and donor numbers (DNs) of ligands, it was found that donicities of N-substituted2-pyrrolidones (Me, Et, Bu, cyclohexyl, and cyclohexylmethyl) are in the range of 26-29, and the DN of 1,3-dimethyl-2-imidazolidone was estimated as 27.8. (c) 2005 Elsevier B.V. All rights reserved.