Hydrazine Capture and N–N Bond Cleavage at Iron Enabled by Flexible Appended Lewis Acids

Incorporation of two 9-borabicyclo[3.3.1]­nonyl substituents within the secondary coordination sphere of a pincer-based Fe­(II) complex provides Lewis acidic sites capable of binding 1 or 2 equiv of N₂H₄. Reduction of the 1:1 Fe:N₂H₄ species affords a rare Fe­(NH₂)₂ complex in which the amido ligands are stabilized through interactions with the appended boranes. The NH₂ units can be released as NH₃ upon protonation and exchanged with exogenous N₂H₄

Tailoring the Electronic Structure of Uranium Mono(imido) Species through Ligand Variation

Uranium mono­(imido) species have been prepared via the oxidation of Cp*U­(^MesPDI^Me)­(THF) (<b>1-Cp*</b>) and [Cp^PU­(^MesPDI^Me)]₂ (<b>1-Cp</b>^<b>P</b>), where Cp* = η⁵-1,2,3,4,5-pentamethylcyclopentadienide, Cp^P = 1-(7,7-dimethylbenzyl)­cyclopentadienide, ^MesPDI^Me = 2,6-[(Mes)­NCMe]₂C₅H₃N, and Mes = 2,4,6-trimethylphenyl, with organoazides. Treating either with N₃DIPP (DIPP = 2,6-diisopropylphenyl) formed uranium­(IV) mono­(imido) complexes, Cp^PU­(NDIPP)­(^MesPDI^Me) (<b>2-Cp</b>^<b>P</b>) and Cp*U­(NDIPP)­(^MesPDI^Me) (<b>2-Cp*</b>), featuring reduced [^MesPDI^Me]⁻. The addition of electron-donating 1-azidoadamantane (N₃Ad) to <b>1-Cp*</b> generated a dimeric product, [Cp*U­(NAd)­(^MesHPDI^Me)]₂ (<b>3</b>), from radical coupling at the <i>p</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>1-</b>^{<i><b>t</b></i>}<b>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>2-</b>^{<i><b>t</b></i>}<b>Bu</b>), was isolated. All isolated complexes were analyzed spectroscopically and structurally, and the dynamic solution behavior was examined using electronic absorption spectroscopy

A Uranium(IV) Triamide Species with Brønsted Basic Ligand Character: Metal–Ligand Cooperativity in the f Block

Deprotonation of the tridentate triamine ligand H₃N₃^Mes ((2,4,6-Me₃C₆H₂N­(H)­CH₂CH₂)₂NH) with 2 equiv of KCH₂Ph followed by treatment with 1 equiv of UCl₄ afforded the diamidoamine uranium complex (THF)₂UCl₂(HN₃^Mes) (<b>1-THF</b>). This species was further derivatized with either OPPh₃ or KCp* to generate (Ph₃PO)­UCl₂(HN₃^Mes) (<b>1-OPPh</b>_<b>3</b>) or Cp*UCl­(HN₃^Mes) (<b>2-Cl</b>), respectively. Deprotonation of <b>2-Cl</b> with ^<i>n</i>BuLi furnished the uranium­(IV) triamido compound Cp*U­(N₃^Mes-LiCl­(THF)₂) (<b>3-LiCl</b>), which is stabilized by the presence of LiCl. <b>3-LiCl</b> reacts readily with alcohols and thiols, including HOPh, HSPh, and HO^<i>t</i>Bu, to furnish the respective products Cp*U­(OPh)­(HN₃^Mes) (<b>2-OPh</b>), Cp*U­(SPh)­(HN₃^Mes) (<b>2-SPh</b>), and Cp*U­(O^<i>t</i>Bu)­(HN₃^Mes) (<b>2-O</b>^{<i><b>t</b></i>}<b>Bu</b>), which show cooperative addition of the H–E (E = O, S) bond across the U–N bond, serving to regenerate the diamidoamine ligand. Similar cooperative addition was noted for <b>3-LiCl</b> with benzophenone, furnishing Cp*U­(N₃^Mes-OCPh₂) (<b>3-OCPh</b>_<b>2</b>), which features new U–O and N–C bonds. The Brønsted basicity of the central nitrogen of <b>3-LiCl</b> was illustrated by addition of PhOAc, which favored α-carbon deprotonation over nucleophilic attack at the carbonyl. All species were subject to a complete spectroscopic and crystallographic analysis, confirming that the reactivity of <b>3-LiCl</b> in fact involves cooperation from the triamido ligand and uranium center

Hydrogen Bonds Dictate O₂ Capture and Release within a Zinc Tripod

Six directed hydrogen bonding (H-bonding) interactions allow for the reversible capture and reduction of dioxygen to a <i>trans</i>-1,2-peroxo within a tripodal zinc­(II) framework. Spectroscopic studies of the dizinc peroxides, as well as on model zinc diazides, suggest H-bonding contributions serve a dominant role for the binding/activation of these small molecules

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

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

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

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