Publication Date:
2012-10-20
Description:
An earlier reported series of the [ Ln (Ur) 4 (H 2 O) 4 ]I 3 ( 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 (H 2 O) 4 ]I 3 , was studied by X-ray diffraction. The most striking feature of the [ Ln (Ur) 4 (H 2 O) 4 ]I 3 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 ](ClO 4 ) 3 · 2Ur and [La(Ur) 7 (OClO 3 )](ClO 4 ) 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.
Print ISSN:
0044-2313
Electronic ISSN:
1521-3749
Topics:
Chemistry and Pharmacology
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