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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Expansion of Low- and Mid-Valent Organometallic Uranium Chemistry

Caleb 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>
2

Open-shell Coordination Compounds based on Cyanide and Scorpionate Ligands / Composés de coordination open-shell basés sur des ligands cyanure et scorpionate

Garnier, 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.
3

Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes

Liang, Shengwen 11 September 2012 (has links)
No description available.

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