Rational design of <scp>pincer‐nickel</scp> complexes for catalytic cyanomethylation of benzaldehyde: A systematic <scp>DFT</scp> study

Dutta, Moumita; Srivastava, H. K.; Kumar, Akshai

doi:10.1002/jcc.26708

Cited by 5 publications

(3 citation statements)

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“…Recently, first-row transition-metal catalysts have also been employed for these Guerbet-type reaction . Considering the fact that one of the early and finest examples of the Guerbet reaction came from the use of Raney nickel in the presence of a strong base; it is interesting to note that the corresponding reports with homogeneous Ni catalysts are very sparse and mainly devoted to α-alkylation of alcohols and ketones apart from related C–C bond forming reactions . The C-C cross-coupling of alcohols was recently reported by Lang and co-workers (Figure ) in which they utilized a Ni(II) 4,6-dimethylpyrimidine-2-thiolate cluster catalyst toward the synthesis of α,β-unsaturated ketones, α-alkylated ketones, and β-alkylated alcohols by simple tuning of the reaction conditions .…”

Section: Introductionmentioning

confidence: 99%

Pincer-Nickel Catalyzed Selective Guerbet-Type Reactions

2021

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We report here the synthesis and characterization of a series of NNN pincer-nickel complexes of the type ( R2 NNN)-NiCl 2 (CH 3 CN) (R = i Pr, t Bu, Cy, Ph, and p-F-C 6 H 4 ) based on bis(imino)pyridine ligands. In solution, these complexes are found to be equilibrium mixtures containing one and two pincer ligands, respectively. While the crystal structure of the former was reported by us recently for R = i Pr, we report the crystal structure of the latter in this study for R = p-F-C 6 H 4 . The considered NNN pincer-Ni complexes have been successfully employed to accomplish the catalytic β-alkylation of several secondary alcohols with a variety of benzyl alcohols at 140 °C with high yields and unprecedented turnovers. A maximum of 92% yield of the β-alkylated product at 18 400 TON was obtained in the reaction of benzyl alcohol with 1-(4-(trifluoromethyl)phenyl)ethane-1-ol in the presence of 0.005 mol % of ( Ph2 NNN)NiCl 2 (CH 3 CN) and 5 mol % of NaO t Bu at 140 °C after 24 h. The reaction exhibits zero-order dependence of rate on catalyst concentration and first-order dependence on the concentration of base, benzyl alcohol, and 1-phenyl ethanol which points to the base-mediated aldol condensation as the rate-determining step. Most of the intermediates involved in catalysis have been identified by HRMS. To the best of our knowledge, this is the first report on a pincer-Ni catalyzed β-alkylation of alcohols and, hitherto, such unprecedented turnovers have not been reported with a homogeneous molecular nickel-based catalyst.

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Section: Introductionmentioning

confidence: 99%

Pincer-Nickel Catalyzed Selective Guerbet-Type Reactions

2021

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“…In this study, the level of theory, B3LYP with empirical dispersion‐GD3 parameter, [ 14 ] is used to find the optimal singlet‐state structures of alkyl carbanions and fluorinated carbanions at the basis set 6‐31++G(d,p), involving the polarization function [ 15 ] and the diffuse function [ 16 ] by using GAUSSIAN16 package. [ 17 ] For NBO analysis, the NBO 6.0 program is used to speculate on the change of hybridization of carbon‐containing lone‐pair orbitals to get stable geometries from primary to secondary carbanions.…”

Section: Methodsmentioning

confidence: 99%

Validation of valence bond and molecular orbital models in analyzing the anionic hyperconjugation effect on the stability of alkyl and fluorinated carbanions in gaseous phase

Nguyen

Tran

2023

J of Physical Organic Chem

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In this paper, the anionic hyperconjugation occurring in alkyl and fluorinated carbanions in the gaseous phase is examined at density functional theory (DFT) at the level of theory B3LYP/6‐31++G (d,p) with empirical dispersion‐GD3 theory. First, a contribution of this study is to confirm that the C‐H bond in (CH3)3C‐H (isobutane) is more acidic than the C‐H bonds in CH3CH2‐H (ethane) and (CH3)2CH‐H (propane) based on a comparison of conjugate base stability. Also, the natural population analysis (NPA) and CHELPG methods are well‐performed for calculating charge distribution on carbon atoms, and in contrast, the Mulliken population is better for hydrogen atoms to describe the anionic hyperconjugation in the valence bond (VB) model. The molecular orbital model accounts for the stability order of alkyl and perfluorinated carbanions through the number, strength, and overlap geometry between the lone electron pair on carbon atom and the vicinal σ*C‐H/σ*C‐F orbitals. On the other hand, the utility of VB theory becomes invalid because of the strong inductive effect of the fluorine element and the steric repulsion among CF3 groups in perfluorinated carbanions. Also, the hybridization of the carbon atom holding the lone electron pair can become more s‐character or p‐character dependent on the size of surrounding groups.

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“…The relativistic compact Stuttgart/Dresden (SDD) effective core potential [69][70][71] is largely used for precious metals, such as Ru 19 and Pt, 72,73 but it is also employed to describe the core electrons of non-precious transition metals, such as Zn 74,75 and Ni, 76 and heavier halogens such as iodine atoms. 77,78 Sousa and collaborators 79 found that use of SDD effective core potential has a very limited impact, in terms of accuracy, in the determination of metal-ligand bond lengths and angles in zinccomplexes, and it is a good and safe alternative to the use of an all-electron basis set.…”

Section: Effective Core Potentialsmentioning

confidence: 99%