Crystal and molecular structure of (NH4)2[UO2(NO3)4] and [(NH4)(18C6)]2[UO2(NO3)4

Abstract

Single crystals of diammonium tetranitratouranylate (NH4)2[UO2(NO3)4] (I) and a new diammonium tetranitratouranylate complex with 18-crown-6 [(NH4)(18C6)]2[UO2(NO3)4] (II) have been synthesized by the reaction of diaquadinitratouranyl tetrahydrate with ammonium nitrate in a nitric acid solution and the reaction of the same reagents with 18C6 in an ethanol solution, respectively. The X-ray diffraction analysis of compounds I and II has been performed. Crystals of compounds I and II are monoclinic, Z = 2, space group P21/n, a = 6.4075(5) A, b = 7.7851(7) A, c = 12.4461(12) A, β = 101.239(1)°, V = 608. 94(9) A3 for compound I and a = 10.542(9) A, b = 8.590(8) A, c = 22.5019(19) A, β = 101.632(1)°, V = 2058.3(3) A3 for compound II. The [UO2(NO3)4]2− complex anion in compounds I and II contains two monodentate and two bidentate cyclic nitrato groups, and the coordination number of uranyl is 6. The 18C6 molecule in the structure of compound II has the classic crown conformation and combined with the ammonium ion by three hydrogen bonds. Compounds I and II formed by electrostatic attraction forces between counterions are stabilized by (NH 4 + )NH...O(NO 3 − ) interionic hydrogen bonds.