Ru complexes containing pyridine dicarboxylate ligands: electronic effects on their catalytic activity toward wateroxidation

2012 ◽  
Vol 155 ◽  
pp. 267-275 ◽  
Author(s):  
Junxue An ◽  
Lele Duan ◽  
Licheng Sun
Keyword(s):  
Catalytic Activity ◽  
Electronic Effects ◽  
Ru Complexes

scholarly journals Electronic effects in mixed N-heterocyclic carbene/phosphite indenylidene ruthenium metathesis catalysts

2019 ◽  
Vol 48 (30) ◽  
pp. 11326-11337 ◽  
Author(s):  
Yannick D. Bidal ◽  
César A. Urbina-Blanco ◽  
Albert Poater ◽  
David B. Cordes ◽  
Alexandra M. Z. Slawin ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Electronic Properties ◽  
Computational Studies ◽  
Electronic Effects ◽  
Metathesis Catalysts ◽  
Shed Light

Experimental and computational studies shed light on the role played by sacrificial ligand electronic properties on catalytic activity.

Synthesis of dipyroromethanes in water and investigation of electronic and steric effects in efficiency of olefin epoxidation by sodium periodate catalyzed by manganese tetraaryl andtransdisubstituted porphyrin complexes

2019 ◽  
Vol 23 (06) ◽  
pp. 671-678 ◽  
Author(s):  
Mojtaba Bagherzadeh ◽  
Mohammad Adineh Jonaghani ◽  
Mojtaba Amini ◽  
Anahita Mortazavi-Manesh
Keyword(s):  
Catalytic Activity ◽  
Reaction Time ◽  
Sodium Periodate ◽  
Acid Catalyst ◽  
Steric Effects ◽  
Electronic Effects ◽  
Good Catalytic Activity ◽  
Epoxidation Of Alkenes ◽  
Epoxidation Of Olefins ◽  
Electronic And Steric Effects

Condensation of pyrrole with various aldehydes in the presence of BF3•etherate as an acid catalyst in water provides good yield of some dipyrromethanes. Prolongation of the reaction time with aldehydes substituted by electron-donating (mesityl) or electron-withdrawing (2,6-dichlorophenyl) groups on the ortho positions of the phenyl did not lead to decomposition or scrambling. Manganese trans disubstituted porphyrin complexes which derive from various dipyrromethanes and manganese tetraaryl porphyrin complexes including various substituents with different steric and electronic properties show good catalytic activity in epoxidation of alkenes by NaIO4in the presence of imidazole (ImH). The study of steric and electronic effects of the catalysts on the epoxidation of olefins shows that Mn-porphyrin complexes with more bulky and electron-releasing groups on meso phenyls could increase the epoxidation yield of most alkenes.

scholarly journals Dinuclear manganese complexes for water oxidation: evaluation of electronic effects and catalytic activity

2014 ◽  
Vol 16 (24) ◽  
pp. 11950 ◽  
Author(s):  
Wael A. A. Arafa ◽  
Markus D. Kärkäs ◽  
Bao-Lin Lee ◽  
Torbjörn Åkermark ◽  
Rong-Zhen Liao ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Water Oxidation ◽  
Manganese Complexes ◽  
Electronic Effects

scholarly journals Effect of Lewis Acids on the Catalyst Activity for Alkene Metathesis, Z-/E- Selectivity and Stability of Tungsten Oxo Alkylidenes

2021 ◽  
Author(s):  
J. Haydée Merino ◽  
Jesús Bernad ◽  
Xavier Solans-Monfort
Keyword(s):  
Catalytic Activity ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
Catalyst Activity ◽  
Electronic Effects ◽  
Activity Increase ◽  
Two Factors ◽  
Hydride Elimination

AbstractLewis acids increase the catalytic activity of classical heterogeneous catalysts and molecular d0 tungsten oxo alkylidenes in a variety of olefin metathesis processes. The formation of labile adducts between the metal complex and the Lewis acid has been observed experimentally and suggested to be involved in the catalyst activity increase. In this contribution, DFT (M06) calculations have been performed to determine the role of Lewis acids on catalyst activity, Z-/E- selectivity and stability by comparing three W(E)(CHR)(2,5-dimethylpyrrolide)(O-2,6-dimesithylphenoxide) (E = oxo, imido or oxo-Lewis acid adduct) alkylidenes. Results show that the formation of the alkylidene—Lewis acid adducts influences the reactivity of tungsten oxo alkylidenes due to both steric and electronic effects. The addition of the Lewis acid on the E group increases its bulkiness and this decreases catalyst Z-selectivity. Moreover, the interaction between the oxo ligand and the Lewis acid decreases the donating ability of the former toward the metal. This is important when the oxo group has either a ligand in trans or in the same plane that is competing for the same metal d orbitals. Therefore, the weakening of oxo donating ability facilitates the cycloaddition and cycloreversion steps and it stabilizes the productive trigonal bipyramid metallacyclobutane isomer. The two factors increase the catalytic activity of the complex. The electron donating tuneability by the coordination of the Lewis acid also applies to catalyst deactivation and particularly the key β-hydride elimination step. In this process, the transition states show a ligand in pseudo trans to the oxo. Therefore, the presence of the Lewis acid decreases the Gibbs energy barrier significantly. Overall, the optimization of the E group donating ability in each step of the reaction makes tungsten oxo alkylidenes more reactive and this applies both for the catalytic activity and catalyst deactivation.

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