Refinement of the structure of NaIO₄

Abstract

NaIO4 has been re-examined. It crystallizes in space group 141/a with a = b = 5"337, c = 11.947 A; Z= 4.Anisotropic refinement reduced R to 8"94% for 740 observed reflexions. The vibrationally corrected I-O length is 1"775 + 7 A.. The structure consists of IOn-anions, slightly compressed in the c direction, and Na + cations, each surrounded by eight oxygen atoms at distances of 2.54 or 2"60/~. In~oducfionSodium periodate together with other periodates e.g. KIO4 (Hylleraas, 1926), crystallizes with the lattice type of scheelite (CaWO4) (Hiorthdahl, 1887). The lattice parameters and the space group C~h-I4Ja were determined by Kirkpatrick & Dickinson (1926) who assigned the iodine and sodium atoms to the two fourfold positions (4a and 4b). The oxygen atom parameters were later determined approximately by Hazlewood (1938).The present reinvestigation was undertaken to provide the more precise dimensions now needed for discussions of the bonding in tetrahedral oxyanions. ExperimentalTetragonal bipyramidal crystals of NaIO4 were obtained from an aqueous solution of a Hopkins & Williams Ltd. product, held slightly above 40 ° C. A small well-developed crystal was placed in a drop of distilled water and was rotated in the water by a fine needle slowly but continuously. The progress of the etching of the surface was observed through a binocular stereomicroscope. In this way a small almost spherical specimen was prepared with an average diameter of 0.1 mm. The specimen was then mounted at random on a special goniometer head (K~ilm~in, 1967) by means of which one of the a axes was properly oriented. Equiinclination multiple-film photographs were taken with Mo K~ radiation for the layers: hOl-->h4l. The intensifies were estimated visually using standard scales, made from one good reflexion on each layer. After the data reduction 927 independentt IFol values were obtained, of which 187 were too weak for observation, mainly due to the absence of the iodine and sodium contributions from hkl reflexions with 2k + l= 2n + 2.Owing to the small diameter of the specimen (/zR= 0.47) RefinementFollowing Hazlewood (1938), the space group representation with the iodine atom at the origin at 4 was used. His oxygen parameters were taken as the starting point for a full-matrix least-squares refinement with a program written by Dr J. S. Stephens for the ATLAS computer. Five independent scale factors were used and all atoms were treated with anisotropic vibrations. In order to correct for anomalous dispersion, complex scattering factors were used for iodine [Af'=-0.64, Af"=2.15, Cromer (1965)]. Form factors for neutral atoms were taken from a recent table supplied by Ibers (1968). The final weighting scheme was w--(7.0 + 0.151Fol + 0"008lFol2) -a .The refinement reduced the unweighted residual R to 8. 94% and R'=[~wAZ)/(~w[kFol2)]l/z to 11.60% for the 740 observed reflexions. The final parameters are shown in Table 1 and the structure factors in Table 2.

Tetrahedral Tellurate

“…The Te−O bond lengths in the anion are significantly shorter than those observed for the telluric acid and other tellurate anions where the Te atoms are coordinated by six O atoms that form an octahedron. – The lengths of the shorter Te−O2 bonds are comparable to those of I−O bonds in the tetrahedral IO 4 − ion. , These facts are consistent with the tetrahedral structure of the current anion, where the Te atom is coordinated by only four O atoms. Yet the Te−O length in the TeO 4 2− anion is long for a tetrahedral oxo anion.…”

Sodium Periodate (NaIO4) in Organic Synthesis

“…Eight oxygen atoms, spaced 2.54 Å and 2.60 Å apart, encircle the Na + ions in sodium metaperiodate (NaIO 4 ), which forms tetragonal crystals (space group I41/a) with somewhat deformed IO -4 ions and average I-O bond lengths of 1.775 Å. 2,3 The synthesis of many bioactive compounds and fine chemicals depends critically on the study of novel oxidative transformations for the creation of heteroatom-heteroatom and carbon-heteroatom bonds. In this context, the intriguing reagent NaIO 4 has garnered more interest since it makes it possible to produce these extraordinary oxidative changes that would be challenging to accomplish in any other way.…”