Hydrothermal Synthesis and Crystal Structures of Na2Be3(SeO3)4·H2O and Cs2[Mg(H2O)6]3(SeO3)4

The selenites, Na 2 Be 3 (SeO 3 ) 4 · H 2 O and Cs 2 [Mg(H 2 O) 6 ] 3 (SeO 3 ) 4 , were synthesized under hydrothermal conditions. The crystal structures of Na 2 Be 3 (SeO 3 ) 4 · H 2 O and Cs 2 [Mg(H 2 O) 6 ] 3 (SeO 3 ) 4 were determined by single-crystal X-ray diffractions. Na 2 Be 3 (SeO 3 ) 4 · H 2 O crystallizes in the triclinic space group P 1 (no. 2) with unit cell parameters a = 4.8493(9), b = 12.013(2), c = 12.077(2) Å, and Z = 2, whereas Cs 2 [Mg(H 2 O) 6 ] 3 (SeO 3 ) 4 crystallizes in the monoclinic space group C 2/ m (no. 12) with lattice cell parameters a = 12.596(6), b = 7.297(4), c = 16.914(8) Å, and Z = 2. Na 2 Be 3 (SeO 3 ) 4 · H 2 O features a three-dimensional open framework structure formed by BeO 4 tetrahedra and SeO 3 trigonal pyramids. Na cations and H 2 O molecules are located in different tunnels. Cs 2 [Mg(H 2 O) 6 ] 3 (SeO 3 ) 4 has a structure composed of isolated [Mg(H 2 O) 6 ] octahedra and SeO 3 trigonal pyramids interacted by hydrogen bonds, and Cs cations are resided in-between. Both compounds were characterized by thermogravimetric analysis and FT-IR spectroscopy.