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Expansion of Low- and Mid-Valent Organometallic Uranium ChemistryCaleb J Tatebe (6812630) 16 August 2019 (has links)
<p>A series of uranium benzyl compounds supported by two
hydrotris(3,5-dimethylpyrazolyl) borate (Tp*) ligands has been synthesized and
characterized. In addition to the
previously reported Tp*<sub>2</sub>U(CH<sub>2</sub>Ph) (<b>2-Bn</b>), examinations of both steric (<i>tert</i>-butyl, <i>iso</i>-propyl)
and electronic (methoxy, picolyl) changes on the aromatic ring led to the
formula Tp*<sub>2</sub>U(CH<sub>2</sub>Ar) (Ar = 4-<i>tert</i>-butylphenyl (<b>2-<i><sup>t</sup></i>Bu</b>), 4-isopropyl (<b>2-<sup>i</sup>Pr</b>), 2-picolyl (<b>2-pyr</b>), 3-methoxyphenyl (<b>2-OMe</b>). Treatment of the entire series
of benzyl compounds with azidotrimethylsilane results in the formation of a
neutral, monomeric U(III) compound, Tp*<sub>2</sub>U(N<sub>3</sub>) (<b>3-N<sub>3</sub></b>), and substituted benzyltrimethylsilane.
While there was no observed change in reactivity among the benzyl compounds and
Me<sub>3</sub>SiN<sub>3</sub>, treatment of these compounds with
triphenylphosphine oxide saw unique carbon-carbon coupling occur for three of
the substituted benzyl compounds. With a single equivalent of OPPh<sub>3</sub>,
the following products were isolated: Tp*<sub>2</sub>U[OP(C<sub>6</sub>H<sub>5</sub>)(C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>C<sub>6</sub>H<sub>5</sub>)]
(<b>4-Ph</b>), Tp*<sub>2</sub>U[OP(C<sub>6</sub>H<sub>5</sub>)(C<sub>6</sub>H<sub>5</sub>-<i>p</i>-<i>i</i>PrC<sub>6</sub>H<sub>4</sub>)]
(<b>4-<sup>i</sup>Pr</b>), Tp*<sub>2</sub>U[OP(C<sub>6</sub>H<sub>5</sub>)(C<sub>6</sub>H<sub>5</sub>-<i>p</i>-<i>t</i>BuC<sub>6</sub>H<sub>4</sub>)]
(<b>4-<i><sup>t</sup></i>Bu</b>),
Tp*<sub>2</sub>U[OP(C<sub>6</sub>H<sub>5</sub>)(C<sub>6</sub>H<sub>5</sub>-<i>m</i>-OCH<sub>3</sub>C<sub>6</sub>H<sub>4</sub>)]
(<b>4-OMe</b>). </p>
<p> A family of uranium(IV) imido
complexes of the form Tp*<sub>2</sub>U(NR) (R = benzyl (<b>7-Bn</b>), <i>para</i>-tolyl (<b>7-Tol</b>), <i>para</i>-methoxyphenyl (<b>7-OMe</b>),
2,6-diethylphenyl (<b>7-detp</b>),
2,6-diisopropylphenyl (<b>7-dipp</b>)) have
been generated by bibenzyl extrusion from <b>2-Bn</b>.
When <b>7-Bn</b> and <b>7-Tol</b>, along with previously reported Tp*<sub>2</sub>U(N-Ph) (<b>7-Ph</b>) and Tp*<sub>2</sub>U(N-Ad) (<b>7-Ad</b>), are treated with isocyanates or
isothiocyanates, they readily undergo [2π+2π]-cycloaddition to generate
κ<sup>2</sup>-ureato and κ<sup>2</sup>-thioureato derivatives, respectively.
Use of phenylisoselenocyanate with <b>7-Tol</b>
and <b>7-Ph</b> generates a rare κ<sup>2</sup>-selenoureato
complex. Treating <b>7-Tol</b> and <b>7-OMe</b> with benzonitrile or
4-cyanopryidine results in unusual products of multiple bond metathesis, namely
κ<sup>1</sup>-amidinate U(IV) complexes. </p>
<p>A family of
dinuclear bis(Tp*) (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) uranium
compounds with conjugated organic linkers was synthesized to explore possible
electronic communication between uranium ions. Trivalent diuranium phenyl alkynyl compounds, Tp*<sub>2</sub>UCC(1,3-C<sub>6</sub>H<sub>4</sub>)CCUTp*<sub>2</sub>
(<b>14-<i>meta</i></b>)
or Tp*<sub>2</sub>UCC(1,4-C<sub>6</sub>H<sub>4</sub>)CCUTp*<sub>2</sub> (<b>14-<i>para</i></b>),
and tetravalent diuranium phenylimido compounds, Tp*<sub>2</sub>U(N-1,3-C<sub>6</sub>H<sub>4</sub>-N)UTp*<sub>2</sub>
(<b>15-<i>meta</i></b>)
and Tp*<sub>2</sub>U(N-1,4-C<sub>6</sub>H<sub>4</sub>-N)UTp*<sub>2</sub> (<b>15-<i>para</i></b>),
were generated from trivalent Tp*<sub>2</sub>UCH<sub>2</sub>Ph. All compounds
were fully characterized both spectroscopically and structurally. The
electronic structures of all derivatives were interrogated using magnetic
measurements, electrochemistry, and were the subject of computational analyses.
All of this data combined established that little electronic communication
exists between the uranium centers in these trivalent and tetravalent diuranium
molecules.</p>
<p>Uranium mono(imido) species have been prepared via oxidation of Cp*U(<sup>Mes</sup>PDI<sup>Me</sup>)(THF)
(<b>16-Cp</b>*) and [Cp<sup>P</sup>U(<sup>Mes</sup>PDI<sup>Me</sup>)]<sub>2</sub>
(<b>16-Cp<sup>P</sup></b>) (Cp* = <i>η</i><sup>5</sup>-1,2,3,4,5-pentamethylcyclopentadienide;
Cp<sup>P</sup> = 1-(7,7-dimethylbenzyl)cyclopentadienide;
<sup>Mes</sup>PDI<sup>Me</sup> = 2,6-((Mes)N=CMe)<sub>2</sub>C<sub>5</sub>H<sub>3</sub>N,
Mes = 2,4,6-trimethylphenyl) with organoazides.
Treating either with N<sub>3</sub>DIPP formed uranium(IV) mono(imido)
complexes, Cp<sup>P</sup>U(NDIPP)(<sup>Mes</sup>PDI<sup>Me</sup>) (<b>17-Cp<sup>P</sup></b>) and Cp*U(NDIPP)(<sup>Mes</sup>PDI<sup>Me</sup>)
(<b>17-Cp*</b>), featuring reduced [<sup>Mes</sup>PDI<sup>Me</sup>]<sup>1-</sup>.
Addition of electron-donating 1-azidoadamantane (N<sub>3</sub>Ad) to <b>16-Cp*</b> generated a dimeric product, [Cp*U(NAd)(<sup>Mes</sup>HPDI<sup>Me</sup>)]<sub>2</sub>
(<b>18</b>), from radical coupling at the <i>para</i>-pyridine position of the
pyridine(diimine) ligand and H-atom abstraction, formed through a monomeric
intermediate that was observed in solution but could not be isolated. To
support this, Cp*U(<i><sup>t</sup></i>Bu-<sup>Mes</sup>PDI<sup>Me</sup>)(THF)
(<b>16-<i><sup>t</sup></i>Bu</b>),
which has a <i>tert</i>-butyl group
protecting the <i>para</i>-position, was
also treated with N<sub>3</sub>Ad,
and the monomeric product, Cp*U(NAd)(<i><sup>t</sup></i>Bu-<sup>Mes</sup>PDI<sup>Me</sup>)
(<b>17-<i><sup>t</sup></i>Bu</b>),
was isolated. All isolated complexes were analyzed spectroscopically and
structurally, and dynamic solution behavior was examined using electronic
absorption spectroscopy. </p>
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Open-shell Coordination Compounds based on Cyanide and Scorpionate Ligands / Composés de coordination open-shell basés sur des ligands cyanure et scorpionateGarnier, Delphine 10 July 2015 (has links)
Cette thèse porte sur la synthèse et la caractérisation de complexes octaédrique de fer(II) et fer(III) coordinés par un ligand tridente de type scorpionate (symétrie fac) et par trois ligands cyanures. Leur utilisation en tant que metalloligand face à des ions métalliques partiellement bloqués est étudiée. Les ligands cyanures, de par leur caractère ambidente, permettent un accès facile aux espèces hétérobimétalliques. De plus, ces ligands sont connus pour transmettre efficacement l'interaction d'échange magnétique et donc pour favoriser la communication électronique intramoléculaire entre les ions métalliques qu'ils relient. La fonctionalisation des ligands scorpionates permet de contrôler les propriétés électroniques intrinsèques des complexes précurseurs de fer, et donc de moduler les propriétés des espèces polynucléaires obtenues à partir de ces dernières par auto-assemblage. Dans cette thèse, un intérêt particulier est porté aux systèmes {FeCo} en raison de leur capacité à présenter une bistabilité électronique (propriétés photomagnétiques ou de molécules/chaines aimants). Les systèmes cyanuré {FeCo} sont particulièrement adaptés pour l'observation de réarrangements électroniques thermo- et/ou photo-induit, comme en témoignent le nombre important de composés cyanurés photomagnétiques dans la littérature. / The work presented in this PhD dissertation focuses on the synthesis and the characterisation of octahedral iron(II) and iron(III) complexes coordinated by a tridentate ligand of the scorpionate family (fac- geometry) and three cyanide ligands. Their use as metalloligands in respect to partially blocked metal ions is studied. Because of their ambidentate character, cyanide ligands open the door to facile synthesis of heterobimetallic species. Moreover, these ligands are known to be efficient magnetic exchange interaction transmitter, thus favouring intramolecular electronic communication between the metal ions they are bridging. The functionalisation of scorpionate ligands allows control over the intrinsic electronic properties of the iron precursor complexes, thus allows to tune the properties of the obtained polynuclear species from the latter by self-assembly. In this PhD dissertation, a particular interest was taken in {FeCo} systems because of their potential ability to exhibit electronic bistability (photomagnetic properties or SMM/SCM behaviour). Cyanide-bridged {FeCo} systems are particularly suitable for the observation of thermally or light-induced electron rearrangements, as testified by the wide range of photomagnetic cyanide-bridged compounds in the literature.
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Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate ComplexesLiang, Shengwen 11 September 2012 (has links)
No description available.
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