THE CRYSTAL STRUCTURE OF SYNTHETIC GRIMSELITE, K3Na[(UO2)(CO3)3](H2O)

Crystals of grimselite, K3Na[(UO2)(CO3)3](H2O), were synthesized by room-temperature evaporation of an aqueous solu-tion. The structure of grimselite is hexagonal, a 9.302(2), c 8.260(3) Å, V 618.9(3) Å3, space group P¯62c, Z = 2. The crystal structure was refined on the basis of F2 for all 546 unique reflections measured using MoK X-radiation and a CCD-based detector to an R1 of 2.55%, calculated using the 459 unique observed reflections with Fo ≥ 4F. Consistent with other uranyl carbonates with a U: C ratio of 1: 3, the structure of grimselite contains the uranyl tricarbonate cluster [(UO2)(CO3)3], which consists of a uranyl hexagonal bipyramid that shares three equatorial edges with (CO3) triangles. The uranyl tricarbonate clusters are oriented perpendicular to [001] and are interconnected through bonds to Na and K polyhedra