Syntheses and structures of [UO2(L)5](ClO4)2 and [U(L′)4(H2O)4](ClO4)4 (L is dimethylformamide, L′ is N,N-dimethylcarbamide)

Resumo

The reaction of aqueous solutions of uranyl perchlorate with selected organic amides was studied in the dark and under the sunlight. The complexes [U^VIO₂(C₃H₇NO)₅](ClO₄)₂ (I) and [U^IV(C₃H₈N₂O)₄(Н₂О)₄](ClO₄)₄ (II), where C₃H₇NO is N,N-dimethylformamide (Dmfa) and C₃H₈N₂O is N,N-dimethylcarbamide (a-Dmur), were studied by X-ray diffraction. Complex II and the complex U^IV(s-Dmur)₄(Н₂О)₄(ClO₄)₄ (III), where s-Dmur is N,N'-dimethylcarbamide, were studied by IR spectroscopy. Crystals I and II are composed of mononuclear [UO₂(Dmfa)₅]²⁺ and [U(Dmur)₄(Н₂О)₄]⁴⁺ groups as uranium-containing structural units belonging to the crystal-chemical groups AМ₇¹ (А = U^VI, М¹ = O^2– and Dmfa) and AМ₈¹ (А = U^IV, М¹ = Dmur and Н₂О) of uranium complexes, respectively. The mononuclear uranium- containing complexes in the crystals of U(IV) and U(VI) perchlorates were found to obey the 14 neighbors rule.