Na4SeO5, a novel Pentaoxoselenate(VI) - Synthesis, charakterisation, and comparison with Na4MoO5

Na4SeO5 was prepared by high pressure solid state reaction at 500 degreesC and at a hydrostatic pressure of 2.5 Gpa from a mixture of Na2O and Na2SeO4 in silver crucibles and Na4MoO5 by solid state reaction at 450 degreesC fr om a mixture of Na2O and MoO3. The crystal structures of both new compounds were solved and refined using X-ray powder methods (Profilematching Na4SeO 5: P (1) over bar, a = 988.3(1), b = 988.4(1), c = 558.6(l)pm, a = 9625(1)d egrees, beta = 96.24(1)degrees, gamma = 113.41(1)degrees, R-p = 0.0783, R-w p = 0,1037. Profilematching Na4MoO5: pi, a = 999.5(1), b = 1002.0(1), c = 5 65.1(1) pm, Rp = 0.0623, alpha = 96.54(1)degrees, beta = 96.29(1)degrees, g amma = 113.35(1)degrees, R-p = 0.0623, R-wp = 0.0867), Both compounds conta in novel XO54- anions of approximately tetragonal pyramidal shape. The crys tal structures are consistent with spectroscopic data (IR, Raman).