
%0 Journal Article
%A Nolan, Annette L. 
%A Wilkes, Eric N. 
%A Hambley, Trevor W. 
%A Allen, Christine C. 
%A Burns, Robert C. 
%A Lawrance, Geoffrey A. 
%T Crystal Structure of Na<emph tye="8">9</emph>[H<emph tye="8">3</emph>W<emph tye="8">12</emph>O<emph tye="8">42</emph>]&middot;24H<emph tye="8">2</emph>O, a Compound Containing the Protonated Paratungstate B Anion ('Acid Paratungstate'), and Cyclic Voltammetry of Acidified [H<emph tye="8">2</emph>W<emph tye="8">12</emph>O<emph tye="8">42</emph>]<emph type="7">10-</emph> Solutions
%J Australian Journal of Chemistry
%D 1999/12/03
%V 52
%N 10
%P 955-964
%K 
%R https://doi.org/10.1071/CH99070
%U https://www.publish.csiro.au/paper/CH99070 
%X Crystallization of a solid at pH 4.0 from an aqueous acidified Rh3+&#8211;&#91;WO4&#93;2&#8722; solution resulted in the isolation of Na9&#91;H3W12O42&#93;&#183;24H 2 O, which contains the protonated paratungstate B anion and which is likely the species identified previously as &#8216;acid paratungstate&#8217;. The compound is triclinic, space group P1&#8211; , a 10.603(2), b 12.134(3), c 14.042(3) &#197;, &#945; 114.78(1), &#946; 101.84(1), &#947; 108.34(1)&#x02DA;, V 1432.9(5) &#197;3 , Z 1, and the structure was solved to an R1 value of 0.0404 (wR 2 0.1108) for 5997 independent observed reflections. The anion exhibits essentially the same isopolytungstate framework as paratungstate B, &#91;H2W12O42&#93;10&#8722; , consisting of two W3O13 and two W3O14 structural subunits linked by shared vertices. Bond valence arguments place two of the hydrogen atoms unequivocally in the internal cavity of the anion, with the remaining hydrogen atom also likely located in this cavity, but disordered over several internal oxygen atoms. The protonation of &#91;H2W12O42 &#93;10&#8722; is shown to lead to species that are electrochemically reducible. Extended-H&#220;ckel molecular orbital calculations confirm that protonation of paratungstate B within the internal cavity leads to a change in composition of the LUMO, now based mainly on electrochemically reducible W3O13 as opposed to (essentially) non-reducible W3O14 structural subunits. This results in species that are considerably more electrochemically active than the unprotonated anion. The role of &#91;H3W12O42&#93;9&#8722; as an intermediate in the polymerization of &#91;WO4&#93;2&#8722; to give the solution form of &psi;-metatungstate, &#91;H7W11O40&#93;7&#8722; , which crystallizes as &#91;H4W11O38&#93;6&#8722; , is also discussed. 
