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The catena-arsenite chain anion, [AsO2]nn−: (H3NCH2CH2NH3)0.5[AsO2] and NaAsO2 (revisited)

 Acta Cryst. (2004). C60, m215–m218 [doi:10.1107/S0108270104007450]

[catena-arsenite chains]The catena-arsenite chain anion, [AsO2]nn−, has been known in minerals for many years. The AsIII atom in this species shows a distinctive pyramidal geometry, due to its stereochemically active lone pair of electrons. The catena-arsenite anion results from these AsO3 pyramids fusing together via O atoms to result in an infinite chain. We have prepared the first example of the [AsO2]nn− grouping accompanied by an organic cation, ethylenediammonium. The discrete [H3NCH2CH2NH3]2+ cations and [AsO2]nn− chain anions interact strongly by way of N–H…O hydrogen bonds.

C. Lee and W. T. A. Harrison