Mechanism of N-heterocyclic carbene-catalyzed chemical fixation of CO2 with aziridines: a theoretical study

RSC Advances ◽  
2014 ◽  
Vol 4 (33) ◽  
pp. 17236-17244 ◽  
Author(s):  
Weiyi Li ◽  
Dongfeng Huang ◽  
Yajing Lv
Keyword(s):  
Theoretical Study ◽  
Active Species ◽  
Catalytic Cycle ◽  
Catalyst Precursor ◽  
Chemical Fixation

Free NHC is a catalyst precursor, while the carboxylate intermediate is the active species in the catalytic cycle.

scholarly journals Theoretical study on the mechanism of iridium-catalyzed γ-functionalization of primary alkyl C–H bonds

2016 ◽  
Vol 94 (12) ◽  
pp. 1028-1037 ◽  
Author(s):  
Zhe Li ◽  
Miaoren Xia ◽  
Russell J. Boyd
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Experimental Observation ◽  
Density Functional ◽  
Theoretical Study ◽  
Reductive Elimination ◽  
Catalytic Cycle ◽  
Catalyst Precursor ◽  
Functional Theory ◽  
Initial Formation

The mechanism of the iridium-catalyzed functionalization of a primary C–H bond at the γ position of an alcohol 5 is investigated by density functional theory (DFT) calculations. A new IrIII–IrV mechanism is found to be more feasible than the previously reported IrI–IrIII mechanism. 10 In the IrIII–IrV mechanism, the reaction begins with the initial formation of (Me4phen)IrIII(H)[Si(OR)Et2]2 from the catalyst precursor, [Ir(cod)OMe]2 (cod = 1,5-cyclooctadiene). The catalytic cycle includes five steps: (1) the insertion of norbornene into the Ir–H bond to produce (Me4phen)IrIII(norbornyl)[Si(OR)Et2]2 (R = –CH(C2H5)C3H7); (2) the Si–H oxidative addition of HSi(OR)Et2 to form (Me4phen)IrVH(norbornyl)[Si(OR)Et2]3; (3) the reductive elimination of norbornane to furnish (Me4phen)IrIII[Si(OR)Et2]3; (4) the intramolecular C–H activation of the primary C–H bond at the γ position; and (5) the Si–C reductive elimination to produce the final product and regenerate the catalyst. The highest barrier in the IrIII–IrV mechanism is 7.3 kcal/mol lower than that of the IrI–IrIII mechanism. In addition, the regioselectivity of the C–H activation predicted by this new IrIII–IrV mechanism is consistent with experimental observation.

scholarly journals A surprising mechanism lacking the Ni(0) state during the Ni(II)-catalyzed P–C cross-coupling reaction performed in the absence of a reducing agent – An experimental and a theoretical study

2020 ◽  
Vol 92 (3) ◽  
pp. 493-503 ◽  
Author(s):  
Réka Henyecz ◽  
Zoltán Mucsi ◽  
György Keglevich
Keyword(s):  
Theoretical Study ◽  
No Reduction ◽  
Active Catalyst ◽  
Theoretical Calculations ◽  
Coupling Reaction ◽  
Reducing Agent ◽  
Catalyst Precursor ◽  
Ni Catalysts ◽  
Optimum Quantity ◽  
Cross Coupling Reaction

AbstractThe Hirao reaction, i.e. the P–C coupling between a bromoarene and a >P(O)H reagent performed in most cases in the presence of a Pd(0) complex incorporating a P-ligand may also be carried out applying a Ni(II) catalyst precursor with or without Zn or Mg as the reducing agent. The Ni catalysts may include P- or N-ligands. B3LYP/6-31G(d,p)//PCM(MeCN) quantum chemical calculations suggested that the mechanism of the NiX2 catalyzed (X=Cl or Br) P–C couplings performed in the absence of a reducing agent, and in the excess of the >P(O)H reagent serving as the P-ligand (via its tautomeric >POH form) is completely different from that of the Pd(OAc)2 promoted version, as no reduction of the Ni(II) occurs. In the two variations mentioned, the active catalyst is the dehydrobrominated species derived from primary complex [(HO)Y2P]2Ni(II)Br2, and the [(HO)Y2P]2Pd(0) complex itself, respectively. Both species undergo temporary oxidation (to “Ni(IV)” and “Pd(II)”, respectively) in the catalytic cycle. During the catalysis with “P2Ni(II)X2”, one of the P-ligands serves the >P(O)H function of the ArP(O)H <  product. The consequence of this difference is that in the Ni(II)-catalyzed case, somewhat less >P(O)H-species is needed than in the Pd(0)-promoted instance. Applying 10 % of the Pd(OAc)2 or NiX2 precursor, the optimum quantity of the P-reagent is 1.3 equivalent and, in the first approach, 1.1 equivalent, respectively. Preparative experiments justified the new mechanism explored. The ligation of Ni(II) was also investigated by theoretical calculations. It was proved that the bis-complexation is the most favorable energetically as compared to the mono-, tri- and tetra-ligation.

scholarly journals Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

2010 ◽  
Vol 6 ◽  
pp. 1167-1173 ◽  
Author(s):  
Yannick Borguet ◽  
Xavier Sauvage ◽  
Guillermo Zaragoza ◽  
Albert Demonceau ◽  
Lionel Delaude
Keyword(s):  
Mixed Valence ◽  
Active Species ◽  
Radical Reactions ◽  
Catalyst Precursor ◽  
Atom Transfer ◽  
Tandem Catalysis ◽  
Ring Closing Metathesis ◽  
Experimental Conditions ◽  
Mixed Valence Compound ◽  
The Individual

The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium–indenylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(3-phenyl-1-indenylidene)(PCy3)] (1) to generate active species in situ. The two catalytic processes were first carried out independently in a case study before the whole sequence was optimized and applied to the synthesis of several polyhalogenated bicyclic γ-lactams and lactones from α,ω-diene substrates bearing trihaloacetamide or trichloroacetate functionalities. The individual steps were carefully monitored by 1H and 31P NMR spectroscopies in order to understand the intimate details of the catalytic cycles. Polyhalogenated substrates and the ethylene released upon metathesis induced the clean transformation of catalyst precursor 1 into the Ru(II)–Ru(III) mixed-valence compound [(p-cymene)Ru(μ-Cl)3RuCl2(PCy3)], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions.

Dual Catalytic Cycle of H2 and H2O Oxidations by a Half-Sandwich Iridium Complex: A Theoretical Study

2019 ◽  
Vol 58 (11) ◽  
pp. 7274-7284 ◽  
Author(s):  
Kei Ikeda ◽  
Yuta Hori ◽  
Muhammad Haris Mahyuddin ◽  
Yoshihito Shiota ◽  
Aleksandar Staykov ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Catalytic Cycle ◽  
Iridium Complex ◽  
Half Sandwich

A theoretical study on the mechanism of ruthenium(ii)-catalyzed phosphoryl-directed ortho-selective C–H bond activations: the phosphoryl hydroxy group triggered Ru(ii)/Ru(0) catalytic cycle

2017 ◽  
Vol 4 (8) ◽  
pp. 1482-1492 ◽  
Author(s):  
Peng Chen ◽  
Ying Sun ◽  
Yile Wu ◽  
Liu (Leo) Liu ◽  
Jun Zhu ◽  
...  
Keyword(s):  
Hydroxy Group ◽  
Theoretical Study ◽  
Catalytic Cycle ◽  
Bond Activations

A theoretical study on the mechanism of ruthenium(ii)-catalyzed phosphoryl-directed ortho-selective C–H bond activations has been reported.

scholarly journals Reduction of Nitrobenzene to Aniline by CO/H2O in the Presence of Palladium Nanoparticles

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 404 ◽  
Author(s):  
Agnieszka Krogul-Sobczak ◽  
Jakub Cedrowski ◽  
Patrycja Kasperska ◽  
Grzegorz Litwinienko
Keyword(s):  
Catalytic Activity ◽  
Palladium Nanoparticles ◽  
Metallic Nanoparticles ◽  
Active Species ◽  
Catalytic Cycle ◽  
Heterocyclic Ligands ◽  
Aromatic Nitrocompounds ◽  
First Time ◽  
Transient Intermediate

The transformation of aromatic nitrocompounds into amines by CO/H2O is catalyzed by palladium(II) complexes. Recently, we have proposed that the catalytic cycle includes Pd0 as the transient intermediate and herein, for the first time, we describe the application of palladium nanoparticles (PdNPs) stabilized by monodentate N-heterocyclic ligands as nanocatalysts facilitating the reduction of Ar–NO2 into Ar–NH2 by CO/H2O. Among the series—Pd(II) complexes, PdNPs and commercial Pdblack—the highest catalytic activity was observed for PdNPs (3.0 ± 0.5 nm) stabilized by 4-Me-pyridine in the presence of 2-Cl-pyridine. The results may be helpful for mechanistic considerations on the role of metallic nanoparticles as active species in other organic processes.

scholarly journals Pd Nanoparticles and Mixture of CO2/CO/O2 Applied in the Carbonylation of Aniline

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 877 ◽  
Author(s):  
Dominik Madej ◽  
Adrian Konopko ◽  
Piotr Piotrowski ◽  
Agnieszka Krogul-Sobczak
Keyword(s):  
Reaction Time ◽  
Palladium Nanoparticles ◽  
High Stability ◽  
Pd Nanoparticles ◽  
Active Species ◽  
Catalytic Cycle ◽  
Aliphatic Amines ◽  
Pyridine Ligand ◽  
Reaction Conditions ◽  
Derivatives Of

CO2 is a compound of high stability which proves useful in some organic syntheses as a solvent or component decreasing explosivity of gases. It is also a good carbonylating agent for aliphatic amines although not for aromatic ones, the latter being carbonylated with phosgene or, as in our previous works, with CO/O2 in the presence of Pd(II) complexes. In this work we have used the mixture of CO/O2 and CO2 for carbonylation of aniline to N,N’-diphenylurea. After optimization of the reaction conditions (56% of CO2 in CO2/CO mixture) we studied the activity of three kinds of pre-catalysts: (a) Pd(II) complexes, (b) Pdblack, and (c) palladium nanoparticles (PdNPs) in the presence of derivatives of pyridine (XnPy). The highest conversion of aniline (with selectivity towards N,N-diphenylurea ca. 90%) was observed for PdNPs. The results show that catalytic cycle involves Pd(0) stabilized by pyridine ligand as active species. Basing on this observation, we put the hypothesis that application of PdNPs instead of Pd(II) complex can efficiently reduce the reaction time.

A theoretical study of the catalytic cycle of ethylene hydrogenation by a bipalladium cluster

2000 ◽  
Vol 10 (2) ◽  
pp. 51-53 ◽  
Author(s):  
Viktor M. Mamaev ◽  
Igor P. Gloriozov ◽  
Dmitrii A. Lemenovskii ◽  
Yurii V. Babin
Keyword(s):  
Theoretical Study ◽  
Catalytic Cycle ◽  
Ethylene Hydrogenation

scholarly journals Theoretical Study on the Catalytic Cycle and Ligands Effect for the Pd(II)-Catalyzed Heck Reaction

2015 ◽  
Vol 16 (0) ◽  
pp. 30-38
Author(s):  
Shohei Sanada ◽  
Takaaki Kuroda ◽  
Michinori Sumimoto ◽  
Kenji Hori
Keyword(s):  
Heck Reaction ◽  
Theoretical Study ◽  
Catalytic Cycle
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