Syntheses and crystal structures of Pb(SeO3)2 and two modifications of Sn(SeO3)2

Single crystals of two modifications of Sn(SeO3)2 have been synthesized from SnCl2, SeO2 and H2O at low-hydrothermal conditions (T = 490 K), tiny crystals of Pb(SeO3)2 were precipitated at T = 363 K from solutions of SeO2 (aq.) and Pb(CH3COO)4 in pure acetic acid. The structures were determined from CCD X-ray diffraction data and refined to R1 = 0.019, 0.029 and 0.045, respectively. α-Sn(SeO3)2: space group Pa3¯, a = 8.1725(5) Å, V = 545.84(6) Å3, Z = 4. β-Sn(SeO3)2 and Pb(SeO3)2: space group P21/c, a = 4.784(1)/4.811(2), b = 8.529(1)/8.768(4), c = 6.943(1)/7.079(3) Å, β = 111.01(1)/110.10(2)°, V = 264.43(7)/280.4(2) Å3, Z = 2. β-Sn(SeO3)2 and Pb(SeO3)2 crystallize isotypic in a structure type known from Ti(SeO3)2, while α-Sn(SeO3)2 is structurally related to Me2+(NO3)2 compounds. Both structure types are built from Me4+O6 (Me = Sn, Pb) octahedra, which are interlinked by trigonal pyramidal SeO3 groups via common corners to framework structures.