[2π+2π] Cycloaddition of Isocyanates to Uranium(IV) Imido Complexes for the Synthesis of U(IV) κ²‑Ureato Compounds

A new family of uranium­(IV) imido complexes of the form Tp*₂U­(NR) (Tp* = hydrotris­(3,5-dimethylpyrazolyl)­borate; R = benzyl (Bn), <i>para</i>-tolyl (<i>p</i>-Tol), 2,6-diethylphenyl (detp), and 2,6-diisopropylphenyl (dipp)) have been generated by bibenzyl extrusion from Tp*₂UBn. Tp*₂U­(NBn), Tp*₂U­(N<i>p</i>-Tol), and Tp*₂U­(Ndetp), along with previously reported Tp*₂U­(NPh) and Tp*₂U­(NAd) (Ad = 1-adamantyl), readily undergo [2π+2π] cycloaddition with isocyanates and isothiocyanates to generate κ²-ureato and κ²-thioureato derivatives, respectively. These new uranium­(IV) complexes were characterized via multinuclear NMR, vibrational and electronic absorption spectroscopies, and, where possible, X-ray crystallography. The steric demands of the ligands were quantitatively assessed using computational modeling, and it was shown that cycloaddition only occurs for imido species where ligands occupy 90% or less of the coordination sphere

La participation du personnel à la gestion de l'entreprise et les stimulants de l'intéressement matériel

Dans les systèmes des Etats socialistes particuliers on applique de très différentes formes et constructions de la participation du personnel à la gestion ainsi que les stimulants de l'intéressement matériel, ce qu'est dicté généralement par l'acceptation de différentes méthodes de diriger les entreprises. La participation du personnel à la gestion de l'entreprise d'Etat socialiste se réduit aux trois modèles de base: le premier parmi eux consiste en formation à ce but d'une forme juridique spécifique sous la forme de l'autogestion ouvrière (Bulgarie, Yougoslavie et Pologne), le deuxième se met en évidence dans les attributions élargies des syndicats professionnels, le dernier cependant consiste en rejet du principe de la direction unipersonnelle en introduisant la gestion collégiale de l'entreprise (Roumanie). A l'égard des formes différenciées dans la gestion de l'économie nationale, les compétences du personnel dans la sphère de la gestion de l'entreprise se forment différamment dans les Etats particuliers, en donnant dans cette sphère les attributions moindres ou plus grandes. Cependant dans tous les Etats on a largement formé les attributions du personnel dans la sphère de décider sur les affaires de travailleur — et spécialement dans la sphère de fixer le montant des primes et des prix. Cela résulte du droit à décider de la division des fonds sociaux et d'existence, ou bien même la décision de leur montant (p. ex. en Hongrie). La participation du personnel à la gestion ainsi que le système convenable des stimulants de l'intéressement matériel ont pour but l'émancipation de l'initiative des travailleurs particuliers. La fixation indépendente par le personnel de la participation aux fonds particuliers sociaux et d'existence et aussi la décision de leur montant constitue un instrument supplémentaire de ce système — mettant en évidence non seulement son caractère de stimulant mais surtout cela témoigne de la réalisation de l'autogestion. Les solutions acceptées dans les Etats socialistes particuliers dans la sphère de la construction des fonds de l'intéressement matériel ne sont pas uniformes. Cela montrent les sources ainsi que les principes de la création des fonds particuliers. Dans les solutions acceptées il paraît cependant une certaine regularité. Tous les fonds de l'intéressement matériel on peut les diviser en deux groupes fondamentaux. Le premier d'entre eux constituent les fonds qui dépendent des effets économico-financiers des entreprises — ainsi nommés les fonds de stimulation. Le deuxième groupe embrassent les fonds où les effets économico-financiers de l'entreprise n'ont aucune ou presque aucune influence. Ainsi ils prennent le caractère d'une certaine assurance des moyns financiers pour payer les dépenses déterminées sociales et d'existence. Du point de vue de la participation du personnel à la gestion plus convenable est le premier modèle des fonds de l'intéressement matériel. Cette conception est une conception cohérente délivrant les stimulants pour ainsi dire déterminés doublement. Premièrement, par la participation active du personnel à la gestion en but d'acquérir des bases élevées pour créer des fonds et deuxièmement par la participation elle-même au fond ainsi calculé. En cas de la deuxième méthode le personnel sera moins actif dans l'intéressement pour améliorer les effets économico-financiers, car ces derniers ne forment pas le montant des fonds de l'intéressement matériel.Digitalizacja i deponowanie archiwalnych zeszytów RPEiS sfinansowane przez MNiSW w ramach realizacji umowy nr 541/P-DUN/201

Exploring the Insertion Chemistry of Tetrabenzyluranium Using Carbonyls and Organoazides

The insertion chemistry of U­(CH₂C₆H₅)₄ (<b>1</b>) was explored with acetone, benzophenone, mesityl azide, and 1-azidoadamantane. Using 2 equiv of acetone affords the double-insertion product U­[OC­(CH₃)₂­(CH₂C₆H₅)]₂­(CH₂C₆H₅)₂­(THF)₂ (<b>2</b>), while using 4 equiv results in the tri-inserted enolate product U­[OC­(CH₃)₂­(CH₂C₆H₅)]₃­[OC­(CH₃)­CH₂]­(THF)₃ (<b>3</b>). Deuterium labeling experiments aided in the assignment of <b>2</b> and <b>3.</b> With 4 equiv of benzophenone, insertion at all U–C bonds is noted, forming U­[OC­(C₆H₅)₂(CH₂C₆H₅)]₄ (<b>4</b>) and the THF adduct U­[OC­(C₆H₅)₂­(CH₂C₆H₅)]₄­(THF) (<b>4-THF</b>). Addition of 4 equiv of N₃Mes to <b>1</b> forms the tetrakis­(triazenido)­uranium­(IV) complex U­[CH₂­(C₆H₅)­NNN­(Mes)-κ²<i>N</i>^1,2]­[CH₂­(C₆H₅)­NNN­(Mes)-κ²<i>N</i>^1,3]₃ (<b>5</b>), while the same reaction with 1-azidoadamantane generates the uranium­(VI) <i>trans</i>-bis­(imido) complex U­(NAd)₂­[CH₂­(C₆H₅)­NNN­(Ad)-κ²<i>N</i>^1,3]₂­(THF) (<b>6</b>). All species were characterized by ¹H NMR and infrared spectroscopy, with select examples being structurally characterized using single-crystal X-ray diffraction

Use of Alkylsodium Reagents for the Synthesis of Trivalent Uranium Alkyl Complexes

A family of rare uranium­(III) alkyl complexes, Tp*₂UR (R = CH₂SiMe₃ (<b>3-CH</b>_<b>2</b><b>SiMe</b>_<b>3</b>), CH₃ (<b>4-CH</b>_<b>3</b>), (CH₂)₃CH₃ (<b>5-(CH</b>_<b>2</b><b>)</b>_<b>3</b><b>CH</b>_<b>3</b>); Tp* = hydrotris­(3,5-dimethylpyrazolyl)­borate), was synthesized by salt metathesis with alkylsodium reagents and Tp*₂UI (<b>2</b>). All compounds were fully characterized using ¹H NMR, infrared, and electronic absorption spectroscopies. Compounds <b>3-CH</b>_<b>2</b><b>SiMe</b>_<b>3</b> and <b>4-CH</b>_<b>3</b> were structurally characterized using X-ray crystallography and have U–C bond distances of 2.601(9) and 2.54(3) Å, respectively

“Oxidative Addition” of Halogens to Uranium(IV) Bis(amidophenolate) Complexes

A series of U­(IV) complexes, (^Rap)₂U­(THF)₂ [R = <i>tert-</i>butyl (<i>t</i>-Bu) (<b>1</b>), adamantyl (Ad) (<b>2</b>), diisopropylphenyl (dipp) (<b>3</b>)], supported by the redox-active 4,6-di-<i>tert</i>-butyl-2-(R)­amidophenolate ligand, have been synthesized by salt metathesis of 2 equiv of the alkali metal salt of the ligand, M₂[^Rap] [M = K (<b>1</b> and <b>2</b>), Na (<b>3</b>)], with UCl₄. Exposure of these uranium complexes to 1 equiv of PhICl₂ results in oxidative addition to uranium, forming the bis-(4,6-di-<i>tert</i>-butyl-2-(R)­iminosemiquinone) ([^Risq]^1–) uranium­(IV) dichloride dimer, [(^Risq)₂UCl]₂(μ²-Cl)₂ [R = <i>t</i>-Bu (<b>4</b>), Ad (<b>5</b>), dipp (<b>6</b>)]. The addition of iodine to <b>1</b> forms (^tBuisq)₂UI₂(THF) (<b>7</b>), while the reactivity of I₂ with <b>2</b> and <b>3</b> results in decomposition. Complexes <b>1</b>–<b>7</b> have been characterized by ¹H NMR and electronic absorption spectroscopies. X-ray crystallography was employed to elucidate structural parameters of <b>2</b>, <b>3</b>, <b>5</b>, and <b>7</b>

New Benzylpotassium Reagents and Their Utility for the Synthesis of Homoleptic Uranium(IV) Benzyl Derivatives

A new family of benzylpotassium reagents, KBn′(<b>1-Bn</b>′) (Bn′ = <i>p</i>-^<i>i</i>PrBn, <i>p</i>-^<i>t</i>BuBn, <i>p</i>-NMe₂Bn, <i>p</i>-SMeBn, <i>m-</i>OMeBn, <i>o-</i>OMeBn, 2-picolyl), was synthesized using a modified literature procedure and characterized by multinuclear NMR spectroscopy. Combining four equivalents of <b>1-Bn</b>′ with UCl₄ at low temperature in THF afforded the homoleptic uranium­(IV) derivatives <b>2-Bn</b>′ (<b>2-</b><i><b>p</b></i><b>-</b>^{<b><i>i</i></b>}<b>Pr</b>,<b> 2-</b><i><b>p</b></i><b>-</b>^{<b><i>t</i></b>}<b>Bu</b>,<b> 2-</b><i><b>p</b></i><b>-NMe</b>_<b>2</b>, <b>2-</b><i><b>p</b></i><b>-SMe</b>,<b> 2-</b><i><b>o</b></i><b>-Picolyl</b>, <b>2-</b><i><b>m</b></i><b>-OMe</b>, <b>2-</b><i><b>o</b></i><b>-OMe</b>). In addition to ¹H NMR spectroscopic characterization, structural studies of five of these organouranium compounds (<b>2-</b><i><b>p</b></i><b>-</b>^{<b><i>i</i></b>}<b>Pr</b>,<b> 2-</b><i><b>p</b></i><b>-</b>^{<b><i>t</i></b>}<b>Bu</b>,<b> 2-</b><i><b>o</b></i><b>-Picolyl</b>, <b>2-</b><i><b>m</b></i><b>-OMe</b>, <b>2-</b><i><b>o</b></i><b>-OMe</b>) were performed, showing that in many cases the benzyl groups are coordinated in an η⁴-fashion, lending stability to these otherwise low-coordinate molecules. In the cases of U­(<i>o-</i>OMeBn)₄ (<b>2-</b><i><b>o</b></i><b>-OMe</b>) and U­(2-picolyl)₄ (<b>2-</b><i><b>o</b></i><b>-Picolyl</b>), heteroatom coordination to the uranium center is observed

New Benzylpotassium Reagents and Their Utility for the Synthesis of Homoleptic Uranium(IV) Benzyl Derivatives

A new family of benzylpotassium reagents, KBn′(<b>1-Bn</b>′) (Bn′ = <i>p</i>-^<i>i</i>PrBn, <i>p</i>-^<i>t</i>BuBn, <i>p</i>-NMe₂Bn, <i>p</i>-SMeBn, <i>m-</i>OMeBn, <i>o-</i>OMeBn, 2-picolyl), was synthesized using a modified literature procedure and characterized by multinuclear NMR spectroscopy. Combining four equivalents of <b>1-Bn</b>′ with UCl₄ at low temperature in THF afforded the homoleptic uranium­(IV) derivatives <b>2-Bn</b>′ (<b>2-</b><i><b>p</b></i><b>-</b>^{<b><i>i</i></b>}<b>Pr</b>,<b> 2-</b><i><b>p</b></i><b>-</b>^{<b><i>t</i></b>}<b>Bu</b>,<b> 2-</b><i><b>p</b></i><b>-NMe</b>_<b>2</b>, <b>2-</b><i><b>p</b></i><b>-SMe</b>,<b> 2-</b><i><b>o</b></i><b>-Picolyl</b>, <b>2-</b><i><b>m</b></i><b>-OMe</b>, <b>2-</b><i><b>o</b></i><b>-OMe</b>). In addition to ¹H NMR spectroscopic characterization, structural studies of five of these organouranium compounds (<b>2-</b><i><b>p</b></i><b>-</b>^{<b><i>i</i></b>}<b>Pr</b>,<b> 2-</b><i><b>p</b></i><b>-</b>^{<b><i>t</i></b>}<b>Bu</b>,<b> 2-</b><i><b>o</b></i><b>-Picolyl</b>, <b>2-</b><i><b>m</b></i><b>-OMe</b>, <b>2-</b><i><b>o</b></i><b>-OMe</b>) were performed, showing that in many cases the benzyl groups are coordinated in an η⁴-fashion, lending stability to these otherwise low-coordinate molecules. In the cases of U­(<i>o-</i>OMeBn)₄ (<b>2-</b><i><b>o</b></i><b>-OMe</b>) and U­(2-picolyl)₄ (<b>2-</b><i><b>o</b></i><b>-Picolyl</b>), heteroatom coordination to the uranium center is observed

“Oxidative Addition” of Halogens to Uranium(IV) Bis(amidophenolate) Complexes

A series of U­(IV) complexes, (^Rap)₂U­(THF)₂ [R = <i>tert-</i>butyl (<i>t</i>-Bu) (<b>1</b>), adamantyl (Ad) (<b>2</b>), diisopropylphenyl (dipp) (<b>3</b>)], supported by the redox-active 4,6-di-<i>tert</i>-butyl-2-(R)­amidophenolate ligand, have been synthesized by salt metathesis of 2 equiv of the alkali metal salt of the ligand, M₂[^Rap] [M = K (<b>1</b> and <b>2</b>), Na (<b>3</b>)], with UCl₄. Exposure of these uranium complexes to 1 equiv of PhICl₂ results in oxidative addition to uranium, forming the bis-(4,6-di-<i>tert</i>-butyl-2-(R)­iminosemiquinone) ([^Risq]^1–) uranium­(IV) dichloride dimer, [(^Risq)₂UCl]₂(μ²-Cl)₂ [R = <i>t</i>-Bu (<b>4</b>), Ad (<b>5</b>), dipp (<b>6</b>)]. The addition of iodine to <b>1</b> forms (^tBuisq)₂UI₂(THF) (<b>7</b>), while the reactivity of I₂ with <b>2</b> and <b>3</b> results in decomposition. Complexes <b>1</b>–<b>7</b> have been characterized by ¹H NMR and electronic absorption spectroscopies. X-ray crystallography was employed to elucidate structural parameters of <b>2</b>, <b>3</b>, <b>5</b>, and <b>7</b>

Synthesis, Characterization, and Stoichiometric U–O Bond Scission in Uranyl Species Supported by Pyridine(diimine) Ligand Radicals

Two uranium­(VI) uranyl compounds, Cp*UO₂­(^MesPDI^Me) (<b>3</b>) and Cp*UO₂(^<i>t</i>Bu-^MesPDI^Me) (<b>3-</b>^{<i><b>t</b></i>}<b>Bu</b>) (Cp* = 1,2,3,4,5-pentamethylcyclopentadienide; ^MesPDI^Me = 2,6-((Mes)­N=CMe)₂C₅H₃N; ^<i>t</i>Bu-^MesPDI^Me = 2,6-((Mes)­N=CMe)₂-<i>p</i>-C­(CH₃)₃C₅H₂N; Mes = 2,4,6-trimethylphenyl), have been synthesized by addition of <i>N</i>-methylmorpholine <i>N</i>-oxide to trianionic pyridine­(diimine) uranium­(IV) precursors, Cp*U­(^MesPDI^Me)­(THF) (<b>1</b>), Cp*U­(^MesPDI^Me)­(HMPA) (<b>1-HMPA</b>), and Cp*U­(^<i>t</i>Bu-^MesPDI^Me)­(THF) (<b>1-</b>^{<i><b>t</b></i>}<b>Bu</b>). These uranyl complexes contain singly reduced pyridine­(diimine) ligands suggesting formation occurs via cooperative ligand/metal oxidation. Treating <b>3</b> or <b>3-</b>^{<i><b>t</b></i>}<b>Bu</b> with stoichiometric equivalents of Me₃SiI results in stepwise oxo silylation to form (Me₃SiO)₂UI₂(^MesPDI^Me) (<b>5</b>) or (Me₃SiO)­UI₂(^<i>t</i>Bu-^MesPDI^Me) (<b>5-</b>^{<i><b>t</b></i>}<b>Bu</b>), respectively. Additional equivalents result in full uranium–oxo bond scission and formation of UI₄(1,4-dioxane)₂ with extrusion of hexamethyldisiloxane. The uranium complexes have been characterized via multinuclear NMR, vibrational, and electronic absorption spectroscopies and, in some cases, X-ray crystallography

Mechanistic Insights into Concerted C–C Reductive Elimination from Homoleptic Uranium Alkyls

A mechanistic study was carried out to probe concerted C–C reductive elimination from homoleptic uranium­(IV) alkyls. The <i>para</i>-chloro uranium­(IV) tetrabenzyl derivative, U­(CH₂–<i>p</i>-ClC₆H₄)₄ (<b>2-</b><i><b>p</b></i><b>-Cl</b>), was synthesized by treating UCl₄ with 4 equivalents of KCH₂–<i>p</i>-Cl-Ph (<b>1-p-Cl</b>) at −108 °C, adding a new member to the previously reported family of uranium alkyl complexes U­(CH₂C₆H₅)₄ (<b>2-Bn</b>), U­(CH₂–<i>p</i>-^<i>i</i>PrC₆H₄)₄ (<b>2-</b><i><b>p</b></i><b>-</b>^{<i><b>i</b></i>}<b>Pr)</b>, U­(CH₂–<i>p</i>^<i>t</i>Bu-C₆H₄)₄ (<b>2-</b><i><b>p</b></i><b>-</b>^{<i><b>t</b></i>}<b>Bu</b>), U­(CH₂–<i>o</i>-OMeC₆H₄)₄ (<b>2-</b><i><b>o</b></i><b>-OMe</b>), and U­(CH₂–<i>m</i>-OMeC₆H₄)₄ (<b>2-</b><i><b>m</b></i><b>-OMe</b>). Each member of this family readily reacts with the redox-active α-diimine ligand, ^MesDAB^Me (^MesDAB^Me = [MesNC­(Me)­C­(Me)NMes]; Mes = 2,4,6-trimethylphenyl), to afford the products from C–C reductive elimination, namely, (^MesDAB^Me)­U­(CH₂Ph′)₂ and Ph′CH₂CH₂Ph′ (Ph′ = <i>p</i>-^<i>i</i>PrC₆H₄, <i>p</i>-^<i>t</i>BuC₆H₄, <i>m</i>-OMeC₆H₄, <i>p</i>-ClC₆H₄). Room-temperature magnetic-susceptibility values, obtained via SQUID magnetometry, show a correlation with an increase in the magnetic moment as the electron-withdrawing character of the substituent increases. Kinetic studies were used to assess the effect of the benzyl substituent on the rate of reductive elimination, showing that reaction rate increases as the electron-withdrawing nature of the substitution increases. Eyring data revealed a large and negative entropy value, indicative of a highly ordered transition state, consistent with the previously reported concerted elimination concluded from crossover experiments