Synthesis, structure and bonding of hexaphenyl thorium(IV): observation of a non-octahedral structure

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.We report herein the synthesis of the first structurally characterized homoleptic actinide aryl complexes, [Li(DME)(3)](2)[Th(C6H5)(6)] (1) and [Li(THF)(12-crown-4)](2)[Th(C6H5)(6)] (2), which feature an anion possessing a regular octahedral (1) or a severely distorted octahedral (2) geometry. The solid-state structure of 2 suggests the presence of pseudo-agostic ortho C-H center dot center dot center dot Th interactions, which arise from sigma(C-H) -> Th(5f) donation. The non-octahedral structure is also favoured in solution at low temperatures.DFG, EXC 314, Unifying Concepts in Catalysi

Synthesis, structure and bonding of hexaphenyl thorium(IV): observation of a non-octahedral structure.

We report herein the synthesis of the first structurally characterized homoleptic actinide aryl complexes, [Li(DME)3]2[Th(C6H5)6] (1) and [Li(THF)(12-crown-4)]2[Th(C6H5)6] (2), which feature an anion possessing a regular octahedral (1) or a severely distorted octahedral (2) geometry. The solid-state structure of 2 suggests the presence of pseudo-agostic ortho C-H···Th interactions, which arise from σ(C-H) → Th(5f) donation. The non-octahedral structure is also favoured in solution at low temperatures

Correction to "Quantifying the σ and π Interactions between U(V) f Orbitals and Halide, Alkyl, Alkoxide, Amide and Ketimide Ligands".

While preparing a follow-up manuscript, we found an error in one of the orbital reduction factors used in our crystal field models, given in Scheme 2. The third equation in that scheme was published as ka2t2 = 1 - 12 N2 2 a'p ; however, the correct formula is k a2t2 = 1 - 12 N'a'p2. (Table Presented)

Correction to "Quantifying the σ and π Interactions between U(V) f Orbitals and Halide, Alkyl, Alkoxide, Amide and Ketimide Ligands".

While preparing a follow-up manuscript, we found an error in one of the orbital reduction factors used in our crystal field models, given in Scheme 2. The third equation in that scheme was published as ka2t2 = 1 - 12 N2 2 a'p ; however, the correct formula is k a2t2 = 1 - 12 N'a'p2. (Table Presented)

Synthesis, Characterization, and Electrochemistry of the Homoleptic f Element Ketimide Complexes [Li]2[M(N═CtBuPh)6] (M = Ce, Th).

Reaction of [Ce(NO3)3(THF)4] with 6 equiv of Li(N═CtBuPh), followed by addition of 0.5 equiv of I2, affords the homoleptic Ce(IV) ketimide [Li]2[Ce(N═CtBuPh)6] (1), which can be isolated in 44% yield after workup. Similarly, reaction of [ThCl4(DME)2] (DME = 1,2-dimethoxyethane) with 6 equiv of Li(N═CtBuPh) in tetrahydrofuran affords the isostructural Th(IV) ketimide [Li]2[Th(N═CtBuPh)6] (2), which can be isolated in 53% yield after workup. Both 1 and 2 were fully characterized, including analysis by X-ray crystallography, allowing for a detailed structural and spectroscopic comparison. The electronic structures of 1 and 2 were also explored with density functional theory and multiconfigurational wave function calculations. Additionally, the redox chemistry of 1 was probed by cyclic voltammetry, which revealed a highly cathodic Ce(IV)/Ce(III) reduction potential, providing evidence for the ability of the ketimide ligand to stabilize high oxidation states of the lanthanides

In Pursuit of Homoleptic Actinide Alkyl Complexes

This Forum Article describes the pursuit of isolable homoleptic actinide alkyl complexes, starting with the pioneering work of Gilman during the Manhattan project. The initial reports in this area suggested that homoleptic uranium alkyls were too unstable to be isolated, but Wilkinson demonstrated that tractable uranium alkyls could be generated by purposeful “ate” complex formation, which serves to saturate the uranium coordination sphere and provide the complexes with greater kinetic stability. More recently, we reported the solid-state molecular structures of several homoleptic uranium alkyl complexes, including [Li­(THF)₄]­[U­(CH₂^tBu)₅], [Li­(TMEDA)]₂[UMe₆], [K­(THF)]₃[K­(THF)₂]­[U­(CH₂Ph)₆]₂, and [Li­(THF)₄]­[U­(CH₂SiMe₃)₆], by employing Wilkinson’s strategy. Herein, we describe our attempts to extend this chemistry to thorium. The treatment of ThCl₄(DME)₂ with 5 equiv of LiCH₂^tBu or LiCH₂SiMe₃ at −25 °C in THF affords [Th­(CH₂^tBu)₅] (<b>1</b>) and [Li­(DME)₂]­[Th­(CH₂SiMe₃)₅ (<b>2</b>), respectively, in moderate yields. Similarly, the treatment of ThCl₄(DME)₂ with 6 equiv of K­(CH₂Ph) produces [K­(THF)]₂[Th­(CH₂Ph)₆] (<b>3</b>), in good yield. Complexes <b>1</b>–<b>3</b> have been fully characterized, while the structures of <b>1</b> and <b>3</b> were confirmed by X-ray crystallography. Additionally, the electronic properties of <b>1</b> and <b>3</b> were explored by density functional theory

Synthesis and Reactivity of a U(IV) Dibenzyne Complex

Reaction of UCl₄ with 6 equiv of 2-Li-C₆H₄CH₂NMe₂ affords the U­(IV) dibenzyne complex [Li]₂[U­(2,3-C₆H₃CH₂NMe₂)₂(2-C₆H₄CH₂NMe₂)₂] (<b>1</b>), which can be isolated as a dark blue solid in 40% yield. Complex <b>1</b> represents a rare example of a structurally characterized dibenzyne complex, and its solid-state metrical parameters suggest that the two benzyne ligands are best described with the dianionic metallacyclopropene resonance form. The reactivity of <b>1</b> with a variety of electrophiles and oxidants, including benzophenone, 1-azidoadamantane, and benzonitrile, was also explored. Reaction of <b>1</b> with 2 equiv of benzophenone affords the insertion product [Li]­[U­(2-C₆H₃CH₂NMe₂-3-C<i>O</i>Ph₂)₂(2-C₆H₄CH₂NMe₂)] (<b>3</b>) as a red-orange solid in 61% yield, concomitant with formation of 1 equiv of 2-Li-C₆H₄CH₂NMe₂. Reaction of <b>1</b> with 2 equiv of PhCN also affords an insertion product, [Li]­[Li­(Et₂O)]­[U­(2,3-C₆H₃CH₂NMe₂)­(2-C₆H₃CH₂NMe₂-3-C­(Ph)<i>N</i>)­(2-C₆H₄CH₂NMe₂)₂] (<b>4</b>), as a green-brown crystalline solid in 21% yield. In an attempt to oxidize <b>1</b> to U­(VI), the reaction of <b>1</b> with 2 equiv of AdN₃, in the presence of 2 equiv of 12-crown-4, was probed. This reaction only yields the U­(IV) insertion product [Li­(12-crown-4)₂]­[Li]­[U­(2-C₆H₃CH₂NMe₂-3-(<i>N</i>-N<i>N-</i>Ad))₂(2-C₆H₄CH₂NMe₂)₂] (<b>5</b>) as a red crystalline solid in 42% yield. No evidence for the formation of a U­(VI) imido complex is observed in the reaction mixture

Synthesis and Reactivity of a U(IV) Dibenzyne Complex

Reaction of UCl₄ with 6 equiv of 2-Li-C₆H₄CH₂NMe₂ affords the U­(IV) dibenzyne complex [Li]₂[U­(2,3-C₆H₃CH₂NMe₂)₂(2-C₆H₄CH₂NMe₂)₂] (<b>1</b>), which can be isolated as a dark blue solid in 40% yield. Complex <b>1</b> represents a rare example of a structurally characterized dibenzyne complex, and its solid-state metrical parameters suggest that the two benzyne ligands are best described with the dianionic metallacyclopropene resonance form. The reactivity of <b>1</b> with a variety of electrophiles and oxidants, including benzophenone, 1-azidoadamantane, and benzonitrile, was also explored. Reaction of <b>1</b> with 2 equiv of benzophenone affords the insertion product [Li]­[U­(2-C₆H₃CH₂NMe₂-3-C<i>O</i>Ph₂)₂(2-C₆H₄CH₂NMe₂)] (<b>3</b>) as a red-orange solid in 61% yield, concomitant with formation of 1 equiv of 2-Li-C₆H₄CH₂NMe₂. Reaction of <b>1</b> with 2 equiv of PhCN also affords an insertion product, [Li]­[Li­(Et₂O)]­[U­(2,3-C₆H₃CH₂NMe₂)­(2-C₆H₃CH₂NMe₂-3-C­(Ph)<i>N</i>)­(2-C₆H₄CH₂NMe₂)₂] (<b>4</b>), as a green-brown crystalline solid in 21% yield. In an attempt to oxidize <b>1</b> to U­(VI), the reaction of <b>1</b> with 2 equiv of AdN₃, in the presence of 2 equiv of 12-crown-4, was probed. This reaction only yields the U­(IV) insertion product [Li­(12-crown-4)₂]­[Li]­[U­(2-C₆H₃CH₂NMe₂-3-(<i>N</i>-N<i>N-</i>Ad))₂(2-C₆H₄CH₂NMe₂)₂] (<b>5</b>) as a red crystalline solid in 42% yield. No evidence for the formation of a U­(VI) imido complex is observed in the reaction mixture