Different Types of Coordinated Urea Molecules in its Complexes with Rare‐Earth Iodides and Perchlorates

Abstract

AbstractAn earlier reported series of the [Ln(Ur)4(H2O)4]I3 (Ln = Y, La, Nd, Eu, Gd, Dy, Ho, Er; Ur = urea) complexes was completed with seven new compounds (Ln = Ce, Pr, Sm, Tb, Tm, Yb, Lu); one of them, [Ce(Ur)4(H2O)4]I3, was studied by X‐ray diffraction. The most striking feature of the [Ln(Ur)4(H2O)4]I3 structures is the presence of two types of coordinated urea molecules. There are two planar symmetric and two non‐planar asymmetric urea molecules. The Ln–O–C bond angles vary in the ranges 163.06–165.71° and 148.42–152.42° for symmetric and asymmetric urea ligands, respectively, correlating with the ionic mode of urea coordination. To elucidate the role of aqua ligands for the urea coordination mode, two water‐free perchlorate complexes, [La(Ur)8](ClO4)3·2Ur and [La(Ur)7(OClO3)](ClO4)2 were synthesized and structurally characterized. In these complexes, all urea molecules are planar symmetric; however, both covalent and ionic types of urea coordination with the La–O–C bond angles varying in the 132.4–142.3° and 145.5–159.1° ranges, respectively can be observed.