The Role of Dynamic Ligand Exchange in the Oxidation Chemistry of Cerium(III)

The CeIII/IV couple is useful for many applications in organic, inorganic, and materials chemistry. However, attaining a general method to access both oxidations states through reversible solution redox chemistry remains challenging. Herein we report the synthesis, characterization, and oxidation chemistry of the novel Ce/Li REMB heterochiral diastereomer, 1-Ce(het). The solution exchange processes of 1-RE(het) (RE ¼ Ce and Yb) were investigated to estimate rates of ligand and cation exchange relevant in homochiral and heterochiral frameworks. A detailed mechanistic investigation following the solution dynamics of 1-Ce(het) revealed reactivity controlled both by ligand reorganization and redistribution processes. Ligand reorganization was responsible for the kinetics associated with the chemical oxidation reaction, whereas ligand redistribution and exchange dictated the isolated product

Cerium(III) and Uranium(IV) Complexes of the 2‑Fluorophenyl Trimethylsilyl Amide Ligand: C–F → Ln/An Interactions that Modulate the Coordination Spheres of f‑Block Elements

2-fluorophenyl trimethylsilyl amide, N­(SiMe₃)­(C₆H₄F)⁻ was shown to engage in stronger C–F → Ce^III interactions than pentafluorophenyl trimethylsilyl amide, N­(SiMe₃)­(C₆F₅)⁻, through a comparative study of the Ce^III model complexes Ce­[N­(SiMe₃)­(C₆H₄F)]₃ (<b>1-F</b>_<b>1</b>) and Ce­[N­(SiMe₃)­(C₆F₅)]₃ (<b>1-F</b>_<b>5</b>). The presence of multiple C–F → U^IV interactions led to complexes <b>2-X</b> (X = Cl, CCPh, OMe) with threefold geometries, featuring a trigonal pyramidal UN₃Cl core in the solid-state structures. Density functional theory calculations were applied to <b>2-Cl</b> to investigate the strength of the C–F → U^IV interactions and the influence of such interactions on resulting geometries

Cerium(III) and Uranium(IV) Complexes of the 2‑Fluorophenyl Trimethylsilyl Amide Ligand: C–F → Ln/An Interactions that Modulate the Coordination Spheres of f‑Block Elements

2-fluorophenyl trimethylsilyl amide, N­(SiMe₃)­(C₆H₄F)⁻ was shown to engage in stronger C–F → Ce^III interactions than pentafluorophenyl trimethylsilyl amide, N­(SiMe₃)­(C₆F₅)⁻, through a comparative study of the Ce^III model complexes Ce­[N­(SiMe₃)­(C₆H₄F)]₃ (<b>1-F</b>_<b>1</b>) and Ce­[N­(SiMe₃)­(C₆F₅)]₃ (<b>1-F</b>_<b>5</b>). The presence of multiple C–F → U^IV interactions led to complexes <b>2-X</b> (X = Cl, CCPh, OMe) with threefold geometries, featuring a trigonal pyramidal UN₃Cl core in the solid-state structures. Density functional theory calculations were applied to <b>2-Cl</b> to investigate the strength of the C–F → U^IV interactions and the influence of such interactions on resulting geometries

Stable Uranium(VI) Methyl and Acetylide Complexes and the Elucidation of an Inverse Trans Influence Ligand Series

Thermally stable uranium­(VI)–methyl and −acetylide complexes: U^VIOR­[N­(SiMe₃)₂]₃ R = −CH₃, −CCPh were prepared in which coordination of the hydrocarbyl group is directed trans to the uranium–oxo multiple bond. The stability of the uranium–carbon bond is attributed to an inverse trans influence. The hydrocarbyl complexes show greater ITI stabilization than that of structurally related U^VIOX­[N­(SiMe₃)₂]₃ (X = F^–, Cl^–, Br^–) complexes, demonstrated both experimentally and computationally. An inverse trans influence ligand series is presented, developed from a union of theoretical and experimental results and based on correlations between the extent of <i>cis</i>-destabilization, the complexes stabilities toward electrochemical reduction, the thermodynamic driving forces for UO bond formation, and the calculated destabilization of axial σ* and π* antibonding interactions

Reductive Cleavage of Nitrite to Form Terminal Uranium Mono-Oxo Complexes

Uranium terminal mono-oxo complexes are prepared with a unique activation of nitrite following reductive cleavage of an N–O bond with loss of nitric oxide. The thermodynamic driving force of UO bond formation differentiates this reactivity from known mechanisms of nitrite reduction, which are typically mediated by proton transfer. Mechanistic details are explored by DFT supporting a simple homolytic cleavage pathway from a κ¹–ONO bound intermediate. Complexes of the formula U^VIOX­[N­(SiMe₃)₂]₃ are formed providing a trigonal bipyramidal framework into which ligands trans to the UO bond may be installed

Reductive Cleavage of Nitrite to Form Terminal Uranium Mono-Oxo Complexes

Uranium terminal mono-oxo complexes are prepared with a unique activation of nitrite following reductive cleavage of an N–O bond with loss of nitric oxide. The thermodynamic driving force of UO bond formation differentiates this reactivity from known mechanisms of nitrite reduction, which are typically mediated by proton transfer. Mechanistic details are explored by DFT supporting a simple homolytic cleavage pathway from a κ¹–ONO bound intermediate. Complexes of the formula U^VIOX­[N­(SiMe₃)₂]₃ are formed providing a trigonal bipyramidal framework into which ligands trans to the UO bond may be installed