Synthesis and X-ray diffraction study of new uranyl malonate and oxalate complexes with carbamide

Two new malonate-containing uranyl complexes with carbamide of the formulas [UO 2 (C 3 H 2 O 4 )( Urea ) 2 ] ( I ) and [UO 2 (C 3 H 2 O 4 )( Urea ) 3 ] ( II ), where Urea is carbamide, and one uranyl oxalate complex of the formula [UO 2 (C 2 O 4 )( Urea ) 3 ] ( III ) were synthesized, and their crystals were studied by X-ray diffraction. The main structural units in crystals I are the electroneutral chains [UO 2 (C 3 H 2 O 4 )( Urea ) 2 ] ∞ belonging to the crystal-chemical group AT 11 M 2 1 ( A = UO 2 2+ , T 11 = C 3 H 2 O 4 2- , M 1 = Urea ) of uranyl complexes. Crystals II and III are composed of the molecular complexes [UO 2 ( L )( Urea ) 3 ], where L = C 3 H 2 O 4 2- or C 2 O 4 2- , belonging to the crystal-chemical group AB 01 M 3 1 ( A = UO 2 2+ , B 01 = C 3 H 2 O 4 2- or C 2 O 4 2- , M 1 = Urea ). The characteristic features of the packing of the uranium-containing complexes are discussed in terms of molecular Voronoi–Dirichlet polyhedra. The effect of the Urea : U ratio on the structure of uranium-containing structural units is considered.