93 research outputs found
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
Complexation and Redox Chemistry of Neptunium, Plutonium and Americium with a Hydroxylaminato Ligand
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, NÂ(SiMe<sub>3</sub>)Â(C<sub>6</sub>H<sub>4</sub>F)<sup>−</sup> was shown to engage in
stronger C–F → Ce<sup>III</sup> interactions than pentafluorophenyl
trimethylsilyl amide, NÂ(SiMe<sub>3</sub>)Â(C<sub>6</sub>F<sub>5</sub>)<sup>−</sup>, through a comparative study of the Ce<sup>III</sup> model complexes CeÂ[NÂ(SiMe<sub>3</sub>)Â(C<sub>6</sub>H<sub>4</sub>F)]<sub>3</sub> (<b>1-F</b><sub><b>1</b></sub>) and CeÂ[NÂ(SiMe<sub>3</sub>)Â(C<sub>6</sub>F<sub>5</sub>)]<sub>3</sub> (<b>1-F</b><sub><b>5</b></sub>). The presence
of multiple C–F → U<sup>IV</sup> interactions led to
complexes <b>2-X</b> (X = Cl, Cî—¼CPh, OMe) with threefold
geometries, featuring a trigonal pyramidal UN<sub>3</sub>Cl 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<sup>IV</sup> 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, NÂ(SiMe<sub>3</sub>)Â(C<sub>6</sub>H<sub>4</sub>F)<sup>−</sup> was shown to engage in
stronger C–F → Ce<sup>III</sup> interactions than pentafluorophenyl
trimethylsilyl amide, NÂ(SiMe<sub>3</sub>)Â(C<sub>6</sub>F<sub>5</sub>)<sup>−</sup>, through a comparative study of the Ce<sup>III</sup> model complexes CeÂ[NÂ(SiMe<sub>3</sub>)Â(C<sub>6</sub>H<sub>4</sub>F)]<sub>3</sub> (<b>1-F</b><sub><b>1</b></sub>) and CeÂ[NÂ(SiMe<sub>3</sub>)Â(C<sub>6</sub>F<sub>5</sub>)]<sub>3</sub> (<b>1-F</b><sub><b>5</b></sub>). The presence
of multiple C–F → U<sup>IV</sup> interactions led to
complexes <b>2-X</b> (X = Cl, Cî—¼CPh, OMe) with threefold
geometries, featuring a trigonal pyramidal UN<sub>3</sub>Cl 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<sup>IV</sup> 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 uraniumÂ(VI)–methyl and −acetylide
complexes: U<sup>VI</sup>ORÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub> R = −CH<sub>3</sub>, −Cî—¼CPh 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<sup>VI</sup>OXÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub> (X = F<sup>–</sup>, Cl<sup>–</sup>, Br<sup>–</sup>) 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 Uî—»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
Uî—»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 κ<sup>1</sup>–ONO bound
intermediate. Complexes of the formula U<sup>VI</sup>OXÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub> are formed providing a trigonal
bipyramidal framework into which ligands trans to the Uî—»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
Uî—»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 κ<sup>1</sup>–ONO bound
intermediate. Complexes of the formula U<sup>VI</sup>OXÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub> are formed providing a trigonal
bipyramidal framework into which ligands trans to the Uî—»O bond
may be installed
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