Synthesis and Crystal Structure of New Iodate Na3Fe[IO3]6 of the A3M[IO3]6 Structural Family (A = Na, K, Rb, Cs, Tl; M = Ti, Fe, Ge, In, Pt)

Crystals of new iodate Na3Fe[IO3](6) were prepared by the hydrothermal synthesis (the unit cell parameters a = 6.6886(2) angstrom, b = 6.7756(3) angstrom, c = 10.1396(6) angstrom, alpha = 74.590(4)degrees, beta = 71.510(4)degrees, gamma = 79.960(4)degrees; sp. gr. P, R = 2.7%). The new compound belongs to the family containing the {M[IO3](6)} structural unit (M = Ti, Ge, In, Pt, Fe3+). The latter is composed of a MO6 octahedron sharing vertices with six [IO3](-) groups. The Na3Fe[IO3](6) structure is the first one, in which an octahedral M site is occupied by Fe3+ cations. The Na atoms are distributed over two sites between the {Fe[IO3](6)}(3-) units and are located in oxygen octahedra. A comparison of the new structure with Rb3In[IO3](6) showed that inversion centers are differently occupied by alkali metals Na and Rb.