Arsenite

For the supporters of Arsenios Autoreianos in the Byzantine Empire, see Arsenite Schism.

In chemistry, an arsenite is a chemical compound containing an arsenic oxyanion where arsenic has oxidation state +3. Note that in fields that commonly deal with groundwater chemistry, arsenite is used generically to identify soluble AsIII anions. IUPAC have recommended that arsenite compounds are to be named as arsenate(III), for example ortho-arsenite is called trioxidoarsenate(III). Ortho-arsenite contrasts to the corresponding anions of the lighter members of group 15, phosphite which has the structure HPO2−3 and nitrite, NO−2 which is bent.[1]

A number of different arsenite anions are known:

  • AsO3−3 ortho-arsenite, an ion of arsenous acid, with a pyramidal shape[1]
  • (AsO−2)n meta-arsenite, a polymeric chain anion.[2]
  • As2O4−5 pyro-arsenite, [O2As−O−AsO2]4−
  • As3O5−7 catena-triarsenite, [O2As−O−As(O)−O−AsO2]5−[3]
  • As4O6−9 catena-tetraarsenite, [O2As−O−As(O)−O−As(O)−O−AsO2]6−[3]
  • As4O4−8 cyclo-tetraarsenite[4]
  • (As6O4−11)n, a polymeric anion

In all of these the geometry around the AsIII centers are approximately trigonal, the lone pair on the arsenic atom is stereochemically active.[1] Well known examples of arsenites include sodium meta-arsenite which contains a polymeric linear anion, (AsO−2)n, and silver ortho-arsenite, Ag3AsO3, which contains the trigonal AsO3−3 anion.

  1. ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  2. ^ Carmalt, C.J & Norman, N.C. (1998). "Chapter 1: Arsenic, antimony and bismuth". In Norman, N.C. (ed.). Chemistry of Arsenic, Antimony and Bismuth. Blackie Academic and Professional. pp. 118–121. ISBN 07514-0389-X.
  3. ^ a b Hamida, M. Ben; Wickleder, M. S. (2006). "Die neuen Catena-Polyarsenite [As3O7]5− und [As4O9]6−". Zeitschrift für anorganische und allgemeine Chemie. 632 (12–13): 2109. doi:10.1002/zaac.200670065. ISSN 0044-2313.
  4. ^ Kang, Dong-Hee; Schleid, Thomas (2006). "Sm2As4O9: Ein ungewöhnliches Samarium(III)-Oxoarsenat(III) gemäß Sm4[As2O5]2[As4O8]". Zeitschrift für anorganische und allgemeine Chemie. 632 (1): 91. doi:10.1002/zaac.200500333. ISSN 0044-2313.