<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*₂U(CH₂Ph) (<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*₂U(CH₂Ar) (Ar = 4-<i>tert</i>-butylphenyl (<b>2-<i>^t</i>Bu</b>), 4-isopropyl (<b>2-ⁱPr</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*₂U(N₃) (<b>3-N₃</b>), and substituted benzyltrimethylsilane. While there was no observed change in reactivity among the benzyl compounds and Me₃SiN₃, 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 OPPh₃, the following products were isolated: Tp*₂U[OP(C₆H₅)(C₆H₅CH₂C₆H₅)] (<b>4-Ph</b>), Tp*₂U[OP(C₆H₅)(C₆H₅-<i>p</i>-<i>i</i>PrC₆H₄)] (<b>4-ⁱPr</b>), Tp*₂U[OP(C₆H₅)(C₆H₅-<i>p</i>-<i>t</i>BuC₆H₄)] (<b>4-<i>^t</i>Bu</b>), Tp*₂U[OP(C₆H₅)(C₆H₅-<i>m</i>-OCH₃C₆H₄)] (<b>4-OMe</b>). </p> <p> A family of uranium(IV) imido complexes of the form Tp*₂U(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*₂U(N-Ph) (<b>7-Ph</b>) and Tp*₂U(N-Ad) (<b>7-Ad</b>), are treated with isocyanates or isothiocyanates, they readily undergo [2π+2π]-cycloaddition to generate κ²-ureato and κ²-thioureato derivatives, respectively. Use of phenylisoselenocyanate with <b>7-Tol</b> and <b>7-Ph</b> generates a rare κ²-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 κ¹-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*₂UCC(1,3-C₆H₄)CCUTp*₂ (<b>14-<i>meta</i></b>) or Tp*₂UCC(1,4-C₆H₄)CCUTp*₂ (<b>14-<i>para</i></b>), and tetravalent diuranium phenylimido compounds, Tp*₂U(N-1,3-C₆H₄-N)UTp*₂ (<b>15-<i>meta</i></b>) and Tp*₂U(N-1,4-C₆H₄-N)UTp*₂ (<b>15-<i>para</i></b>), were generated from trivalent Tp*₂UCH₂Ph. 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(^MesPDI^Me)(THF) (<b>16-Cp</b>*) and [Cp^PU(^MesPDI^Me)]₂ (<b>16-Cp^P</b>) (Cp* = <i>η</i>⁵-1,2,3,4,5-pentamethylcyclopentadienide; Cp^P = 1-(7,7-dimethylbenzyl)cyclopentadienide; ^MesPDI^Me = 2,6-((Mes)N=CMe)₂C₅H₃N, Mes = 2,4,6-trimethylphenyl) with organoazides. Treating either with N₃DIPP formed uranium(IV) mono(imido) complexes, Cp^PU(NDIPP)(^MesPDI^Me) (<b>17-Cp^P</b>) and Cp*U(NDIPP)(^MesPDI^Me) (<b>17-Cp*</b>), featuring reduced [^MesPDI^Me]^1-. Addition of electron-donating 1-azidoadamantane (N₃Ad) to <b>16-Cp*</b> generated a dimeric product, [Cp*U(NAd)(^MesHPDI^Me)]₂ (<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>^t</i>Bu-^MesPDI^Me)(THF) (<b>16-<i>^t</i>Bu</b>), which has a <i>tert</i>-butyl group protecting the <i>para</i>-position, was also treated with N₃Ad, and the monomeric product, Cp*U(NAd)(<i>^t</i>Bu-^MesPDI^Me) (<b>17-<i>^t</i>Bu</b>), was isolated. All isolated complexes were analyzed spectroscopically and structurally, and dynamic solution behavior was examined using electronic absorption spectroscopy. </p>

<div><div><div><p>The chemistry of the f-block is relatively unknown when compared to the rest of the periodic table. Transition metals and main group elements have enjoyed thorough study and development over the last 200 years, while many of the lanthanides and actinides weren’t even discovered until the 1940’s. This is troublesome, as knowledge of these elements is critical for environmental, industrial and technological advances. Understanding bonding motifs and reactivity pathways is fundamental to advancing the field of f-block chemistry. The use of redox- active ligands has aided in the construction of new bonding modes and discovery of new reaction pathways by providing electrons for these transformations. A particularly successful partnership is formed when redox-active ligands are combined with lanthanides, as these elements are usually considered redox-restricted. A series of lanthanide complexes featuring the iminoquinone ligand in three oxidation states will be discussed. The use of the ligands as a source of electrons for reactivity is also described, with new bonding motifs for lanthanides being realized. The iminoquinone ligand can also serve to break bonds. The uranyl (UO22+) ion is notoriously difficult to handle due to its strong U-O multiple bonds. To overcome this, we developed a series of uranyl complexes and studied the ability of the iminoquinone ligand to serve as an electron source for reduction of uranium, with concomitant U-O bond cleavage.</p></div></div></div>