The periodatonickelates are a series of anions and salts of

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

complexed to the

periodate Periodate is an anion composed of iodine and oxygen. It is one of a number of oxyanions of iodine and is the highest in the series, with iodine existing in oxidation state +7. Unlike other perhalogenates, such as perchlorate, it can exist in two ...

anion. The diperiodatonickelates with nickel in the +4

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

are powerful oxidising agents that are capable of oxidising

bromate The bromate anion, BrO, is a bromine-based oxoanion. A bromate is a chemical compound that contains this ion. Examples of bromates include sodium bromate, (), and potassium bromate, (). Bromates are formed many different ways in municipal drinki ...

perbromate In chemistry, the perbromate ion is the anion having the chemical formula . It is an oxyanion of bromine, the conjugate base of perbromic acid, in which bromine has the oxidation state +7. Unlike its chlorine () and iodine () analogs, it is diff ...

. Sodium nickel periodate, NaNiIO₆·0.5H₂O and potassium nickel periodate, KNiIO₆·0.5H₂O were discovered in 1949 by P. Ray and B. Sarma. These

double salt A double salt is a salt that contains two or more different cations or anions. Examples of double salts include alums (with the general formula ) and Tutton's salts (with the general formula ). Other examples include potassium sodium tartrate, ammo ...

s are coloured dark purple. The salts were made by oxidising

nickel sulfate Nickel(II) sulfate, or just nickel sulfate, usually refers to the inorganic compound with the formula NiSO4(H2O)6. This highly soluble blue green coloured salt is a common source of the Ni2+ ion for electroplating. Approximately 40,000 tonnes ...

mixed with

potassium periodate Potassium periodate is an inorganic salt with the molecular formula KIO4. It is composed of a potassium cation and a periodate anion and may also be regarded as the potassium Salt (chemistry), salt of periodic acid. Note that the pronunciation is ...

(or

sodium periodate Sodium periodate is an inorganic salt, composed of a sodium cation and the periodate anion. It may also be regarded as the sodium salt of periodic acid. Like many periodates, it can exist in two different forms: sodium ''meta''periodate (formula‍ ...

) with the alkali

persulfate A persulfate (sometimes known as peroxysulfate or peroxodisulfate) is a compound containing the anions or . The anion contains one peroxide group per sulfur center, whereas in , the peroxide group bridges the sulfur atoms. In both cases, sulfu ...

salt in boiling water. Similar solids exist for other alkalis such as RbNiIO₆·0.5H₂O ,CsNiIO₆·0.5H₂O and NH₄NiIO₆·0.5H₂O. The crystalline salts are insoluble in water, acids or bases.

Ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

can also be used as the oxidiser. The colour is due to absorbance of visible light shorter than 800 nm, with a peak at 540 nm. The crystal structure of all the solids has

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unchan ...

''P''312. It contains layers of hexagon arrangements of oxygen, in every second layer the alkali atoms fill one third of the holes, and in the alternative layers

iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...

and nickel fill two thirds of the holes. Analogous mixed periodates also exist for some other tetravalent metals, including

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors s ...

tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...

and

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

. The diperiodatonickelates, also known as dihydroxydiperiodatonickelates, contain nickel in the +4 oxidation state along with two periodate anions. The i(OH)₂[IO₅OHsub>2">O<sub>5<_sub>OH.html" ;"title="i(OH)₂[IO₅OH">i(OH)₂[IO₅OHsub>2sup>6− ion can form a brown salt with sodium: Na₄H₂ i(OH)₂ O₅OHsub>2�6H₂O, another acidic sodium salt Na₅ i(OH)₂ O₅OHsub>2�H₂O and another orange salt with cobalt: [Co(ethylenediamine)₃]₂Ni(OH)₂[IO₅OH]₂. Diperiodatometalates with the same formula also exist for palladium and nickel. Similar diperiodatometalates can also be made for Cu, Ag, Au, Ru and Os. Diperiodatonickelate is a strong oxidiser. It can dissolve in water in alkaline conditions. An equilibrium between several ions is produced, depending on pH and concentration: i(OH)₂[IO₃(OH)₃sub>2">O<sub>3<_sub>(OH)<sub>3<_sub>.html" ;"title="i(OH)₂[IO₃(OH)₃">i(OH)₂[IO₃(OH)₃sub>2sup>2−, [Ni(OH)₂[IO₃(OH)₃][IO₄(OH)₂³⁻. The ability to oxidise bromate to perbromate is unusual, and very few reagents can do this. The reaction occurs by Ni(IV) changing to Ni(III) with the release of

hydroxyl radical The hydroxyl radical is the diatomic molecule . The hydroxyl radical is very stable as a dilute gas, but it decays very rapidly in the condensed phase. It is pervasive in some situations. Most notably the hydroxyl radicals are produced from the ...

which can react with bromate. Ni(III) converts BrO₄²⁻ radical to perbromate BrO₄⁻. A solid monoperiodatonickelate salt KNiIO₆·0.5H₂O dissolves in a

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

and

solution to yield diperiodatonickelate in solution.

References

{{Reflist, 30em Periodates Nickel complexes Oxidizing agents