imido complexes
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2021 ◽  
Author(s):  
Nadia Leonard ◽  
Teera Chantarojsiri ◽  
Joseph Ziller ◽  
Jenny Yang

Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. There has been renewed interest on their use in molecular systems, where they can be installed using charged functionalities. Manga-nese(V) salen nitrido complexes (salen = N,N’-ethylenebis(salicylideneaminato)) appended with a crown ether unit con-taining a Na+ (1-Na), K+, (1-K), Ba2+ (1-Ba), Sr2+ (1-Sr), La3+ (1-La), or Eu3+ (1-Eu) cation were investigated to experimen-tally demonstrate the effect of cation-induced electric fields on pKa, E1/2, and the effective bond dissociation free energy (BDFE) of N–H bonds. The series, which includes the manganese (V) salen nitrido without a crown appended, spans 4 units of charge. Bounds for the pKa values of the transient imido complexes were determined by UV-visible and 1H NMR spectroscopy. These values, together with the reduction potentials for the Mn(VI/V) couple measured by cyclic voltamme-try in acetonitrile, were used to calculated the N–H BDFEs of the imidos. Despite spanning >700 mV and >9 pKa units across the series, the hydrogen atom BDFE only spans ~ 5 kcal/mol (between 76 and 81 kcal/mol). These results suggest that incorporation of cationic functionalities is an effective strategy for accessing wide ranges of reduction potentials and pKa while minimally affecting BDFE, which is essential to modulating electron, proton, or hydrogen atom transfer path-ways.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jingzhen Du ◽  
Iskander Douair ◽  
Erli Lu ◽  
John A. Seed ◽  
Floriana Tuna ◽  
...  

AbstractDisproportionation, where a chemical element converts its oxidation state to two different ones, one higher and one lower, underpins the fundamental chemistry of metal ions. The overwhelming majority of uranium disproportionations involve uranium(III) and (V), with a singular example of uranium(IV) to uranium(V/III) disproportionation known, involving a nitride to imido/triflate transformation. Here, we report a conceptually opposite disproportionation of uranium(IV)-imido complexes to uranium(V)-nitride/uranium(III)-amide mixtures. This is facilitated by benzene, but not toluene, since benzene engages in a redox reaction with the uranium(III)-amide product to give uranium(IV)-amide and reduced arene. These disproportionations occur with potassium, rubidium, and cesium counter cations, but not lithium or sodium, reflecting the stability of the corresponding alkali metal-arene by-products. This reveals an exceptional level of ligand- and solvent-control over a key thermodynamic property of uranium, and is complementary to isolobal uranium(V)-oxo disproportionations, suggesting a potentially wider prevalence possibly with broad implications for the chemistry of uranium.


Chem ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 1666-1680
Author(s):  
John A. Seed ◽  
Letitia Birnoschi ◽  
Erli Lu ◽  
Floriana Tuna ◽  
Ashley J. Wooles ◽  
...  

Author(s):  
Karsten Meyer ◽  
Weiqing Mao ◽  
Dominik Fehn ◽  
Frank W. Heinemann ◽  
Andreas Scheurer ◽  
...  
Keyword(s):  

2021 ◽  
Author(s):  
Karsten Meyer ◽  
Weiqing Mao ◽  
Dominik Fehn ◽  
Frank W. Heinemann ◽  
Andreas Scheurer ◽  
...  
Keyword(s):  

Author(s):  
Antonis M. Messinis ◽  
Martin J. Hanton ◽  
Philip W. Dyer

Tungsten imido complexes, in combination with EtAlCl2, were found to be efficient pro-catalysts for selective dimerization of 1-hexene to methyl-branched dodecenes, products that can be used for the production of jet and diesel engine fuels.


2020 ◽  
Vol 2020 (37) ◽  
pp. 3573-3579
Author(s):  
Johannes Martin ◽  
Jens Langer ◽  
Holger Elsen ◽  
Sjoerd Harder

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