Organouranium chemistry

<h2 id="history">History</h2>
<p>The development of organouranium compounds started in <a href="/facts/World_War_II/2efV5L1U">World War II</a> when the <a href="/facts/Manhattan_Project/gtg8yRK2">Manhattan Project</a> required volatile uranium compounds for 235U/238U <a href="/facts/Isotope/KD9B1y6o">isotope</a> separation. For example, <a href="/facts/Henry_Gilman/LgcyRRTk">Henry Gilman</a> attempted to synthesize compounds like tetramethyluranium, and others worked on uranium <a href="/facts/Metal_carbonyl/KzJBcMzU">metal carbonyls</a>, but none of the efforts met success due to organouranium instability. After the discovery of <a href="/facts/Ferrocene/jKtu9Cp8">ferrocene</a> in 1951, Todd Reynolds and <a href="/facts/Geoffrey_Wilkinson/BQ3GXMga">Geoffrey Wilkinson</a> in 1956 synthesized the uranium <a href="/facts/Metallocene/AecA5Qrk">metallocene</a> Cp3UCl from <a href="/facts/Sodium_cyclopentadienide/l7JaX1NP">sodium cyclopentadienide</a> and <a href="/facts/Uranium_tetrachloride/Pp4eeTVw">uranium tetrachloride</a> as a stable but extremely air-sensitive compound. In it, the U-Cl bond is an <a href="/facts/Ionic_bond/R6nUJI5u">ionic bond</a>, while the bonds with the three <a href="/facts/Cyclopentadienyl_complex/rezSmzLI">cyclopentadienyl</a> ligands are covalent of the type found in <a href="/facts/Sandwich_compound/uhupMGDU">sandwich compounds</a> with involvement of the uranium 5f <a href="/facts/Atomic_orbital/tKhgl6mL">atomic orbitals</a>.
</p><p><a href="/facts/Ernst_Otto_Fischer/v8zCR6Ke">Ernst Otto Fischer</a> in 1962 discovered <a href="/facts/Tetrakis(cyclopentadienyl)uranium(IV)/c85axeDU">tetracyclopentadienyluranium</a> Cp4U by reaction of KCp with UCl4 (6% yield) as a compound stable in air as a solid but not in solution. A zero <a href="/facts/Molecular_dipole_moment/G1vRqruD">molecular dipole moment</a> and <a href="/facts/IR_spectroscopy/u1Hzx617">IR spectroscopy</a> revealed that it was also a <a href="/facts/Sandwich_compound/uhupMGDU">sandwich compound</a> with uranium in a <a href="/facts/Tetrahedral_molecular_geometry/583AL1sP">tetrahedral molecular geometry</a>. In 1970, Fischer added Cp3U to the list of known organouranium compounds by reduction of Cp4U with elemental uranium.
</p><p>In 1968, the group of <a href="/facts/Andrew_Streitwieser/7kd6Irup">Andrew Streitwieser</a> prepared the stable but <a href="/facts/Pyrophoric/1b8Sl2AJ">pyrophoric</a> compound <a href="/facts/Uranocene/7cJHsK0X">uranocene</a> (COT)2U, which has an atom of uranium sandwiched between two <a href="/facts/Cyclooctatetraenide_anion/kkWW1bwk">cyclooctatetraenide anions</a> (D8h <a href="/facts/Molecular_symmetry/BrDxAkTK">molecular symmetry</a>). The uranium f orbitals interact substantially with the <a href="/facts/Aromaticity/wK0DzRY6">aromatic</a> rings just as the d-orbitals in <a href="/facts/Ferrocene/jKtu9Cp8">ferrocene</a> interact with the Cp ligands. Uranocene differs from ferrocene because its <a href="/facts/HOMO/XyofpH0p">HOMO</a> and <a href="/facts/LUMO/XyofpH0p">LUMO</a> are centered on the metal and not on the rings and all reactions thus involve the metal often resulting in ligand - metal cleavage.
</p><p>Uranocenes show ease of reduction of U(IV) compounds to U(III) compounds; otherwise they are fairly unreactive. A close relative that does have sufficient reactivity, obtained by reaction of uranocene with <a href="/facts/Uranium_borohydride/n9aB4nhf">uranium borohydride</a> is the half-sandwich compound (COT)U(BH4)2 discovered in 1983 by the group of M.J. Ephritikhine. Compounds of this type react in many different ways, for instance alkylation at uranium with <a href="/facts/Organolithium_reagent/xgYnjhP3">organolithium reagents</a> or conversion to hybrid sandwich compounds.
</p><p>Other organouranium compounds are inverted uranocenes with a COT ligand in between two uranium atoms or uranium sandwich compounds with <a href="/facts/Pentalene/VGhJgys6">pentalenide</a> ligands instead of COT ligands.
</p><p>Several anionic homoleptic uranium(V) alkyls are known in the form of their lithium etherate salts, including [UR8]3–, with R = Me, CH2TMS, CH2<i>t</i>Bu.  The uranium(V) [U(CH2TMS)6]– has been characterized crystallographically, while the thermally unstable neutral, homoleptic uranium(VI) complex U(CH2TMS)6 was identified spectroscopically.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> A number of anionic uranium(IV) and uranium(V) methyls (including [UMe6]–, [UMe7]3–, and [U2Me10]2–) have also been characterized crystallographically.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a>
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<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Organoactinide_chemistry/HKYuv9vl">Organoactinide chemistry</a></li>
<li><a href="http://www.sciencemag.org/cgi/content/abstract/217/4564/989">A 1982 review of the organouranium and organothorium chemistry</a></li>
<li><a href="https://onlinelibrary.wiley.com/doi/10.1002/anie.202005138">The Exceptional Diversity of Homoleptic Uranium–Methyl Complexes</a></li></ul>

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

<ol>
<li id="fn:1"><p>D. Seyferth (2004). "Uranocene. The First Member of a New Class of Organometallic Derivatives of the f Elements". Organometallics. 23 (15): 3562–3583. doi:10.1021/om0400705. <a href="https://doi.org/10.1021%2Fom0400705" target="_blank">https://doi.org/10.1021%2Fom0400705</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Johnson, Sara A.; Bart, Suzanne C. (2015-04-23). "Achievements in uranium alkyl chemistry: celebrating sixty years of synthetic pursuits". Dalton Transactions. 44 (17): 7710–7726. doi:10.1039/C4DT01621A. ISSN 1477-9234. <a href="https://pubs.rsc.org/en/content/articlelanding/2015/dt/c4dt01621a" target="_blank">https://pubs.rsc.org/en/content/articlelanding/2015/dt/c4dt01621a</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Sears, Jeffrey D.; Sergentu, Dumitru‐Claudiu; Baker, Tessa M.; Brennessel, William W.; Autschbach, Jochen; Neidig, Michael L. (2020-08-03). "The Exceptional Diversity of Homoleptic Uranium–Methyl Complexes". Angewandte Chemie International Edition. 59 (32): 13586–13590. doi:10.1002/anie.202005138. ISSN 1433-7851. <a href="https://onlinelibrary.wiley.com/doi/10.1002/anie.202005138" target="_blank">https://onlinelibrary.wiley.com/doi/10.1002/anie.202005138</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
</ol>

Organouranium chemistry open-in-new

Organouranium chemistry