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·<i>x</i>H₂O, 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 <i>Cmca</i> (No. 64), with <i>a</i> = 7.17890(10) Å, <i>b</i> = 18.0925(2) Å, <i>c</i> = 12.6972(2) Å, and <i>Z</i> = 4; Rb₃Ga₅(SeO₃)₈(HSeO₃)₂·0.5H₂O, triclinic, space group <i>P</i>-1 (No. 2), with <i>a</i> = 10.7727(2) Å, <i>b</i> = 12.5372(3) Å, <i>c</i> = 12.6952(3) Å, α = 87.210(10)°, β = 85.447(10)°, γ = 72.519(10)°, and <i>Z</i> = 2; RbGaSe₂O₆·H₂O, triclinic, space group <i>P</i>-1 (No. 2), with <i>a</i> = 8.7027(6) Å, <i>b</i> = 9.7622(7) Å, <i>c</i> = 15.3347(14) Å, α = 105.622(4)°, β = 90.210(4)°, γ = 116.385(2)°, and <i>Z</i> = 2