The first hexaoxoselenate(VI) - Synthesis and characterization of Na-12(SeO6)(SeO4)(3)

Pure Na-12(SeO6)(SeO4)(3) has been prepared by solid state reaction at 500 degreesC from a mixture of Na2O and Na2SeO4 in silver crucibles. The crysta l structure has been determined from single crystal data (Pnma, a = 1577.2( 7), b = 781.7(3), c = 1475.5(7) pm, Z = 4, R1 = 0.030, wR2 = 0.058, 2480 ob served reflections [I-o greater than or equal to 2 sigma (I-o)]). Na-12(SeO 6)(SeO4)(3) contains novel SeO66- anions. There exists an unexpected topolo gical relationship between the (SeO6Na8Na2Na4/2a)-Na-i-Na-a part of the str ucture and the MoCl2 structure type (Mo(6)Cl(8)(1)Cl(2)(a)qCl(4/2)(a)). The srystal structure as determined is consistent with spectroscopic data (IR, Raman, Se-77-MAS-NMR).