eCite Digital Repository

Theoretical investigation into the mechanism of cyanomethylation of aldehydes catalyzed by a nickel pincer complex in the absence of base additives

Citation

Ariafard, A and Ghari, H and Khaledi, Y and Bagi, AH and Wierenga, TS and Gardiner, MG and Canty, AJ, Theoretical investigation into the mechanism of cyanomethylation of aldehydes catalyzed by a nickel pincer complex in the absence of base additives, ACS Catalysis, 6, (1) pp. 60-68. ISSN 2155-5435 (2016) [Refereed Article]

Copyright Statement

Copyright 2015 American Chemical Society

DOI: doi:10.1021/acscatal.5b01642

Abstract

Density functional theory (DFT) was used to study the reaction mechanism of cyanomethylation of aldehydes catalyzed by nickel pincer complexes under base-free conditions. The C-bound cyanomethyl complex, which was initially thought to be the active catalyst, is actually a precatalyst, and in order for the catalytic reaction to commence, it has to convert to the less-stable N-bound isomer. The carbon–carbon bond formation then proceeds via direct coupling of the N-bound isomer and the aldehyde to give a zwitterionic intermediate with a pendant alkoxide function, which is further stabilized by hydrogen-bonding interaction with water molecules (or alcohol product). The N-bound alkoxide group of the zwitterionic intermediate is subsequently substituted by MeCN via an associative mechanism, followed by deprotonation of the coordinated MeCN to afford the final product. It was found that the transition structure for the exchange reaction (substitution of MeCN for the alkoxide group) is the highest energy point on the catalytic cycle, and its energy crucially influences the catalyst efficiency. The Ni complexes ligated by bulky and weak trans-influencing pincer ligands are not appropriate catalysts for the cyanomethylation reaction due to the involvement of very-high-energy transition structures for the exchange reaction. In contrast, benzaldehydes with electron-withdrawing substituents are capable of stabilizing the exchange reaction transition structure due to the increased stability of the zwitterionic intermediate, leading to acceleration of the catalytic reaction.

Item Details

Item Type:Refereed Article
Keywords:organonickel, nickel catalysis, pincer, nickel pincer, DFT, density functional theory, catalytic reaction, nickel complexes, cyanomethylation, aldehyde
Research Division:Chemical Sciences
Research Group:Other Chemical Sciences
Research Field:Organometallic Chemistry
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Chemical Sciences
Author:Ariafard, A (Associate Professor Alireza Ariafard)
Author:Wierenga, TS (Miss Tanita Wierenga)
Author:Gardiner, MG (Associate Professor Michael Gardiner)
Author:Canty, AJ (Professor Allan Canty)
ID Code:105625
Year Published:2016
Web of Science® Times Cited:4
Deposited By:Chemistry
Deposited On:2016-01-11
Last Modified:2017-10-25
Downloads:0

Repository Staff Only: item control page