Inner sphere electron transfer

<h2 id="taubes-experiment">Taube's experiment</h2>
<p>The discoverer of the inner sphere mechanism was <a href="/facts/Henry_Taube/pweqLu4D">Henry Taube</a>, who was awarded the <a href="/facts/Nobel_Prize_in_Chemistry/8Nb8Ajjy">Nobel Prize in Chemistry</a> in 1983 for his pioneering studies.  A particularly historic finding is summarized in the abstract of the seminal publication.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
</p>
<p>"When Co(NH3)5Cl++ is reduced by Cr++ in <a href="/facts/Molar_concentration/P2WL5b9q">M</a> [meaning 1 M]  HClO4, 1 Cl− appears attached to Cr for each Cr(III) which is formed or Co(III) reduced.  When the reaction is carried on in a medium containing radioactive Cl, the mixing of the Cl− attached to Cr(III) with that in solution is less than 0.5%.  This experiment shows that transfer of Cl to the reducing agent from the oxidizing agent is direct…"</p>
<p>The paper and the excerpt above can be described with the following equation:
</p>
[CoCl(NH3)5]2+  +  [Cr(H2O)6]2+ →  [Co(NH3)5(H2O)]2+  +  [CrCl(H2O)5]2+
<p>The point of interest is that the chloride that was originally bonded to the cobalt, the oxidant, becomes bonded to chromium, which in its +3 <a href="/facts/Oxidation_state/W53W6s6V">oxidation state</a>, forms kinetically inert bonds to its <a href="/facts/Ligand/6etB3qeW">ligands</a>.  This observation implies the intermediacy of the bimetallic complex [Co(NH3)5(<i>μ</i>-Cl)Cr(H2O)5]4+, wherein "<i>μ</i>-Cl" indicates that the chloride bridges between the Cr and Co atoms, serving as a ligand for both.  This chloride serves as a conduit for electron flow from Cr(II) to Co(III), forming Cr(III) and Co(II).
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Inner_sphere_complex/PUrTtoGs">Inner sphere complex</a></li>
<li><a href="/facts/Outer_sphere_electron_transfer/k9pG0mMX">Outer sphere electron transfer</a></li>
<li><a href="/facts/Solvated_electron/mLplrtI8">Solvated electron</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Inner-sphere electron transfer". doi:10.1351/goldbook.I03052 <a href="/wiki/International_Union_of_Pure_and_Applied_Chemistry" target="_blank">/wiki/International_Union_of_Pure_and_Applied_Chemistry</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Taube, H.; Myers, H.; Rich, R. L. (1953). "The Mechanism of Electron Transfer in Solution". Journal of the American Chemical Society. 75: 4118–4119. doi:10.1021/ja01112a546. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
</ol>

Inner sphere electron transfer open-in-new

Inner sphere electron transfer