
%0 Journal Article
%A Nolan, Annette L. 
%A Allen, Christine C. 
%A Burns, Robert C. 
%A Craig, Donald C. 
%A Lawrance, Geoffrey A. 
%T Monomeric and Dimeric Cobalt(III) Polyoxomolybdates: Crystal Structures and Cyclic Voltammetry of Na<emph tye="8">3</emph> &#91;H<emph tye="8">6</emph>CoMo<emph tye="8">6</emph>O<emph tye="8">24</emph>&#93;.8H<emph tye="8">2</emph>O and K<emph tye="8">6</emph> &#91;H<emph tye="8">4</emph>Co<emph tye="8">2</emph>Mo<emph tye="8">10</emph>O<emph tye="8">38</emph>&#93;.7H<emph tye="8">2</emph>O
%J Australian Journal of Chemistry
%D 1998/10/05
%V 51
%N 9
%P 825-834
%K 
%R https://doi.org/10.1071/C97218
%U https://www.publish.csiro.au/paper/C97218 
%X The crystal structures of Na3 &#91;H6CoMo6O24&#93;.8H2O and K6 &#91;H4Co2Mo10O38&#93;.7H2O have been determined by X-ray diffraction. The monomer, Na3 &#91;H6CoMo6O24&#93;.8H2O, is triclinic, space group P-1, a 6&#183;451(1), b 10&#183;866(2), c 10&#183;922(2) &#197;, &#945; 109&#183;20(1), &#946; 106&#183;90(1), &#947; 95&#183;43(1)&#176;, V 676&#183;3(2) &#197;3, Z 1, and the structure was solved to an R1 value of 0&#183;0243 (wR2 0&#183;0784) for 3761 independent observed reflections. The anion exhibits the well known Anderson structure with six octahedral MoO6 edge-sharing units surrounding the central &#8216;CoO6&#8217; octahedron, with all metals in a common plane. The dimer, K6 &#91;H4Co2Mo10O38&#93;.7H2O, is monoclinic, space group P21/c, a 11&#183;795(5), b 11&#183;626(2), c 29&#183;731(13) &#197;, &#946; 95&#183;33(2)&#176;, V 4059(3) &#197;3, Z 4, and the structure was solved to an R1 value of 0&#183;0215 (wR2 0&#183;1040) for 6546 independent observed reflections. The anion can be derived from the monomeric hexamolybdocobaltate(III) ion by removing one &#8216;MoO5&#8217; unit (ignoring the hydrogen atoms) from each of two monomer anions, turning one 180&#176; around a CoO6 octahedral diagonal, and joining them to create two CoO6 octahedra sharing an edge. Cyclic voltammetry shows that both anions are irreversibly reduced at low pH values (4&#183;0&#8211;4&#183;5), likely as a result of chemical reactions following the initial reduction steps. At higher pH values (4&#183;5&#8211;5&#183;4), a change in speciation occurs in both cases, most likely the result of the formation of less highly protonated species, which also display irreversible electrochemical behaviour. 
