New Selenites: Hydrothermal Syntheses, Crystal Structures, and Characterization of Rb3HGa2(OH)2(SeO3)4, Rb3Ga5(SeO3)8(HSeO3)2·0.5H2O, and RbGa(SeO3)2·H2O

Three new gallium selenites, Rb3HGa2(OH)2(SeO3)4, Rb3Ga5(SeO3)8(HSeO3)2·0.5H2O, and RbGa­(SeO3)2·H2O, have been synthesized by hydrothermal reactions using Rb2CO3, Ga­(NO3)3·xH2O, and SeO2 as reagents. Rb3HGa2(OH)2(SeO3)4 consists of unidimensional corner-linked chains of GaO4(OH)2 that are connected by a SeO3 group, whereas Rb3Ga5(SeO3)8(HSeO3)2·0.5H2O and RbGa­(SeO3)2·H2O exhibit three-dimensional frameworks consisting of three, mutually perpendicular, eight-membered rings (8-MRs). In all three reported materials, Se4+ is in an asymmetric coordination environment attributable to the stereoactive lone pair. Ion-exchange reactions, infrared spectroscopy, thermal analysis, elemental analysis, and dipole moment calculations for the reported materials are also presented. Crystal data: Rb3HGa2(OH)2(SeO3)4, orthorhombic, space group Cmca (No. 64), with a = 7.17890(10) Å, b = 18.0925(2) Å, c = 12.6972(2) Å, and Z = 4; Rb3Ga5(SeO3)8(HSeO3)2·0.5H2O, triclinic, space group P-1 (No. 2), with a = 10.7727(2) Å, b = 12.5372(3) Å, c = 12.6952(3) Å, α = 87.210(10)°, β = 85.447(10)°, γ = 72.519(10)°, and Z = 2; RbGaSe2O6·H2O, triclinic, space group P-1 (No. 2), with a = 8.7027(6) Å, b = 9.7622(7) Å, c = 15.3347(14) Å, α = 105.622(4)°, β = 90.210(4)°, γ = 116.385(2)°, and Z = 2.