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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>T. Ozeki</dc:contributor>
  <dc:contributor>H. T. Evans Jr.</dc:contributor>
  <dc:contributor>C. Rong</dc:contributor>
  <dc:contributor>G.B. Jameson</dc:contributor>
  <dc:contributor>M.T. Pope</dc:contributor>
  <dc:creator>M.H. Dickman</dc:creator>
  <dc:date>2000</dc:date>
  <dc:description>&lt;p&gt;Reduction&lt;span&gt;&amp;nbsp;&lt;/span&gt;of the α-Keggin anion [X&lt;small&gt;&lt;sup&gt;&lt;i&gt;n&lt;/i&gt;+&lt;/sup&gt;&lt;/small&gt;O&lt;small&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;/small&gt;W&lt;small&gt;&lt;sub&gt;12&lt;/sub&gt;&lt;/small&gt;O&lt;small&gt;&lt;sub&gt;36&lt;/sub&gt;&lt;/small&gt;]&lt;small&gt;&lt;sup&gt;[8&amp;nbsp;−&amp;nbsp;&lt;i&gt;n]−&lt;/i&gt;&lt;/sup&gt;&lt;/small&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;(X&amp;nbsp;=&amp;nbsp;H&lt;small&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;/small&gt;&lt;small&gt;&lt;sup&gt;2+&lt;/sup&gt;&lt;/small&gt;, B&lt;small&gt;&lt;sup&gt;3+&lt;/sup&gt;&lt;/small&gt;, Si&lt;small&gt;&lt;sup&gt;4+&lt;/sup&gt;&lt;/small&gt;) by six electrons results in the known tungsten “brown” species [X&lt;small&gt;&lt;sup&gt;&lt;i&gt;n&lt;/i&gt;+&lt;/sup&gt;&lt;/small&gt;O&lt;small&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;/small&gt;(H&lt;small&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;/small&gt;O)&lt;small&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;/small&gt;W&lt;small&gt;&lt;sup&gt;IV&lt;/sup&gt;&lt;/small&gt;&lt;small&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;/small&gt;W&lt;small&gt;&lt;sup&gt;VI&lt;/sup&gt;&lt;/small&gt;&lt;small&gt;&lt;sub&gt;9&lt;/sub&gt;&lt;/small&gt;O&lt;small&gt;&lt;sub&gt;33&lt;/sub&gt;&lt;/small&gt;]&lt;small&gt;&lt;sup&gt;[8&amp;nbsp;−&amp;nbsp;&lt;i&gt;n&lt;/i&gt;]−&lt;/sup&gt;&lt;/small&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in which three W atoms have been reduced from W&lt;small&gt;&lt;sup&gt;VI&lt;/sup&gt;&lt;/small&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;to W&lt;small&gt;&lt;sup&gt;IV&lt;/sup&gt;&lt;/small&gt;, forming a metal–metal bonded triad. The W&lt;small&gt;&lt;sup&gt;IV&lt;/sup&gt;&lt;/small&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;atoms have terminal&lt;span&gt;&amp;nbsp;&lt;/span&gt;water&lt;span&gt;&amp;nbsp;&lt;/span&gt;coordinated in place of terminal oxo groups. Additional tungstate can condense onto these&lt;span&gt;&amp;nbsp;&lt;/span&gt;water&lt;span&gt;&amp;nbsp;&lt;/span&gt;molecules in aqueous solution between pH&amp;nbsp;=&amp;nbsp;4 and 6.5 to form the species reported here, [(XO&lt;small&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;/small&gt;)W&lt;small&gt;&lt;sup&gt;IV&lt;/sup&gt;&lt;/small&gt;&lt;small&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;/small&gt;W&lt;small&gt;&lt;sup&gt;VI&lt;/sup&gt;&lt;/small&gt;&lt;small&gt;&lt;sub&gt;17&lt;/sub&gt;&lt;/small&gt;O&lt;small&gt;&lt;sub&gt;62&lt;/sub&gt;&lt;/small&gt;H&lt;small&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/small&gt;]&lt;small&gt;&lt;sup&gt;&lt;i&gt;y&lt;/i&gt;−&lt;/sup&gt;&lt;/small&gt;. The boron derivative (X&amp;nbsp;=&amp;nbsp;B&lt;small&gt;&lt;sup&gt;3+&lt;/sup&gt;&lt;/small&gt;) is more stable than the metatungstate (X&amp;nbsp;=&amp;nbsp;H&lt;small&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;/small&gt;&lt;small&gt;&lt;sup&gt;2+&lt;/sup&gt;&lt;/small&gt;), both of which have been characterized by&lt;span&gt;&amp;nbsp;&lt;/span&gt;elemental analysis,&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;small&gt;&lt;sup&gt;183&lt;/sup&gt;&lt;/small&gt;W NMR&lt;span&gt;&amp;nbsp;&lt;/span&gt;and X-ray crystal structure analysis. Eight additional tungstate groups condense in the form of a partial Keggin structure containing two triads and one dyad which is rotated 60° relative to a hypothetical α-isomer.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1039/A905539H</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Royal Society of Chemistry</dc:publisher>
  <dc:title>Polyoxometalates from heteropoly "brown" precursors. A new structural class of mixed valence heteropolytungstates, [(XO4)W3IVW17VIO 62Hx]n-</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>