Synthesis, spectroscopic and structural studies of alkali metal–nickel periodates MNilO6(M = Na, K, Rb, Cs or NH4)

Abstract

The dark red-purple nickel(IV) periodataes MNilO₆(M = Na, K, Rb, Cs or NH₄) have been prepared by peroxohexaoxodisulfate oxidation of mixtures of nickel(II) salts, MNO₃ and periodate ions in hot aqueous solution. Powder X-ray diffraction studies showed that the structures adopted the space group P312, with hexagonal close-packed layers of oxide ions. One-third of the octahedral holes in every second layer contained M ions, and in the other layers one-third of the octahedral holes contained I and one-third Ni. The Ni–O,I–O, Ni ⋯ I and Ni ⋯ Ni distances have been determined by a combination of nickel and iodine K-edge extended X-ray absorption fine structure (EXAFS) data. IR, Raman and UV/VIS spectroscopic data for MNiIO₆ were obtained. Iodine K-edge EXAFS data have also been obtained for the related periodates M′M″IO₆(M″= K or Rb; M″= Ge, Sn, Pb or Mn).