Crystal structure of tetra-ammonium uranyl tricarbonate

Crystals of the title compound are monoclinic, a= 10·68, b= 9·38, c= 12·85, β= 96° 27′, Z= 4, space group C2/c. The structure was solved by Patterson and electronic-density syntheses by use of three-dimensional counter data, and refined by least-squares to R 0·076 for 1833 reflections. The uranium(VI) atom is in an eight-coordinate distorted hexagonal environment. The linear uranyl group is perpendicular to the equatorial plane in which three carbonate groups are chelated. The NH4+ groups which fill holes in the structure link the anions through hydrogen bonding.