Periodatonickelates

The periodatonickelates are a series of anions and salts of nickel complexed to the periodate anion. The diperiodatonickelates with nickel in the +4 oxidation state are powerful oxidising agents that are capable of oxidising bromate to perbromate.

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 salts are coloured dark purple.[1] The salts were made by oxidising nickel sulfate mixed with potassium periodate (or sodium periodate) with the alkali persulfate salt in boiling water.[1] 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.[2] Ozone can also be used as the oxidiser.[2] The colour is due to absorbance of visible light shorter than 800 nm, with a peak at 540 nm.[2] The crystal structure of all the solids has space group P312. 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 and nickel fill two thirds of the holes.[2] Analogous mixed periodates also exist for some other tetravalent metals, including manganese, germanium, tin and lead.[2]

The diperiodatonickelates, also known as dihydroxydiperiodatonickelates,[3] contain nickel in the +4 oxidation state along with two periodate anions. The [Ni(OH)2[IO5OH]2]6− ion can form a brown salt with sodium: Na4H2[Ni(OH)2[IO5OH]2]·6H2O, another acidic sodium salt Na5[Ni(OH)2[IO5OH]2]·H2O and another orange salt with cobalt: [Co(ethylenediamine)3]2Ni(OH)2[IO5OH]2.[4][5] Diperiodatometalates with the same formula also exist for palladium and nickel. Similar diperiodatometalates can also be made for Cu, Ag Au, Ru and Os.[4] 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: [Ni(OH)2[IO3(OH)3]2]2−, [Ni(OH)2[IO3(OH)3][IO4(OH)2]]3−.[6] 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 which can react with bromate. Ni(III) converts BrO42− radical to perbromate BrO4−.[6] A solid monoperiodatonickelate salt KNiIO6·0.5H2O dissolves in a potassium hydroxide and potassium periodate solution to yield diperiodatonickelate in solution.[7]

References

  1. 1 2 Ray, P.; Sarma, B. (11 May 1946). "Tetrapositive Nickel as Alkali Nickel Periodates". Nature. 157 (3993): 627. doi:10.1038/157627a0.
  2. 1 2 3 4 5 Currie, David B.; Levason, William; Oldroyd, Richard D.; Weller, Mark T. (1994). "Synthesis, spectroscopic and structural studies of alkali metal–nickel periodates MNilO6(M = Na, K, Rb, Cs or NH4)". J. Chem. Soc., Dalton Trans. (9): 1483–1487. doi:10.1039/DT9940001483.
  3. ↑ Li, Zhi-Ting; Chang, Qing; Li, Bao-Wen; Yang, Li-Ting; Wang, An-Zhou (May 2000). "Kinetics and Mechanism of Oxidation of Ethylenediamine by Dihydroxydiperidatonickelate(Ⅳ) Complex Ion in Alkaline Medium". Retrieved 3 June 2016.
  4. 1 2 Dengel, Andrew C.; El-Hendawy, Ahmed M.; Griffith, William P.; Mostafa, Sahar I.; Williams, David J. (1992). "Transition-metal periodato complexes. Their preparations and properties as catalytic oxidants, and X-ray crystal structure of Na4 K[Au{IO5(OH)}2]·KOH·15H2O". J. Chem. Soc., Dalton Trans. (24): 3489–3495. doi:10.1039/DT9920003489.
  5. ↑ Mukherjee, H. G.; Mandal, Bhansidhar; De, Shyamali (9 October 1984). "Preparation and studies of the complex periodatoferrate (III) hexahydrate and periodatonickelate (IV) monohydrate". Chemischer Informationsdienst. 15 (41). not consulted
  6. 1 2 Bilehal, Dinesh C.; Kulkarni, Raviraj M.; Nandibewoor, Sharanappa T. (January 2002). "Kinetics and Mechanism of Oxidation of Bromate by Diperiodatonickelate(IV) in Aqueous Alkaline Medium--A Simple Method for Formation of Perbromate". Inorganic Reaction Mechanisms. 4 (1-2): 103–109. doi:10.1080/1028662021000020244.
  7. ↑ Hiremath, Chanabasayya V.; Hiremath, Deepak C.; Nandibewoor, Sharanappa T. (May 2007). "Ruthenium(III) catalysed oxidation of gabapentin (neurontin) by diperiodatonickelate(IV) in aqueous alkaline medium: A kinetic and mechanistic study". Journal of Molecular Catalysis A: Chemical. 269 (1-2): 246–253. doi:10.1016/j.molcata.2007.01.024.
This article is issued from Wikipedia - version of the 11/20/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.