Structural Diversity of Sheets in Rubidium Uranyl Oxoselenates: Synthesis and Crystal Structures of Rb 2 [(UO 2 )(SeO 4 ) 2 (H 2 O)](H 2 O), Rb 2 [(UO 2 ) 2 (SeO 4 ) 3 (H 2 O) 2 ](H 2 O) 4 , and Rb 4 [(UO 2 ) 3 (SeO 4 ) 5 (H 2 O)]

Single crystals of three rubidium uranyl selenates, Rb 2 [(UO 2 )(SeO 4 ) 2 (H 2 O)](H 2 O) ( 1 ), Rb 2 [(UO 2 ) 2 (SeO 4 ) 3 (H 2 O) 2 ](H 2 O) 4 ( 2 ), and Rb 4 [(UO 2 ) 3 (SeO 4 ) 5 (H 2 O)] ( 3 ), have been prepared by evaporation from aqueous solutions made out of mixtures of uranyl nitrate, selenic acid and Rb 2 CO 3 . The structures of all compounds have been solved by direct methods on the basis of X‐ray diffraction data sets. The crystallographic data are as follows: ( 1 ): orthorhombic, Pna 2 1 , a = 13.677(2), b = 11.8707(13), c = 7.6397(9) Å, V = 1240.4(3) Å 3 , R 1 = 0.045 for 2396 independent observed reflections; ( 2 ): triclinic, P 1¯, a = 8.4261(12), b = 11.8636(15), c = 13.3279(18) Å, α = 102.612(10), β = 107.250(10), γ = 102.510(10)°, V = 1183.7(3) Å 3 , R 1 = 0.067 for 4762 independent observed reflections; ( 3 ): orthorhombic, Pbnm , a = 11.3761(14), b = 15.069(2), c = 19.2089(17) Å, V = 3292.9(7) Å 3 , R 1 = 0.075 for 3808 independent observed reflections. The structures of the phases 1 , 2 , and 3 are based upon uranyl selenate hydrate sheets composed from corner‐sharing pentagonal [UO 7 ] 8— bipyramids and [SeO 4 ] 2— tetrahedra. In the crystal structure of 1 , the sheets have composition [(UO 2 )(SeO 4 ) 2 (H 2 O)] 2— and run parallel to (001). The interlayer contains Rb + cations and additional H 2 O molecules. In structure of 2 , the [(UO 2 ) 2 (SeO 4 ) 3 (H 2 O) 2 ] 2— sheets are oriented parallel to (101). Highly disordered Rb + cations and H 2 O molecules are located between the sheets. The structure of 3 is based upon [(UO 2 ) 3 (SeO 4 ) 5 (H 2 O)] 4— sheets stacked parallel to (010) and contains Rb + cations in the interlayers. The topologies of the uranyl oxoselenate sheets observed in the structures of 1 , 2 , and 3 are related to the same simple and highly‐symmetric graph consisting of 3‐connected white and 6‐connected black vertices.