Nickel Complexes Bearing N,N,O-Tridentate Salicylaldiminato Ligand: Efficient Catalysts for Imines Formation via Dehydrogenative Coupling of Primary Alcohols with Amines

Abstract

Treatment of salicylaldiminato ligand L1H−L2H (L1H = 2,4-di-tert-butyl-6-((quinolin-8-ylimino)methyl)phenol; L2H = 2,4-di-tert-butyl-6-(((2-(diethylamino)ethyl)imino)methyl)phenol) with Ni(OAc) 2 •4H 2 O in refluxing ethanol afforded nickel complexes [(L1)Ni(OAc)] (1) and [(L2)Ni-(OAc)] (2), respectively. Reaction of L3H (L3H = (2,4-di-tertbutyl-6-(((2-(pyridin-2-yl)ethyl)imino)methyl)phenol)) with Ni-(OAc) 2 •4H 2 O in the presence of excess triethylanmine gave the dual ligands coordinated nickel complex [(L2) 2 Ni] ( 3). Complexes 1−3 were well characterized by high-resolution mass spectrometry, infrared spectroscopy, elemental analysis, and X-ray diffraction analysis. All the three Ni(II) complexes exhibited efficient activity and good selectivity in the acceptorless dehydrogenative coupling of alcohols and amines to produce imines and diimines. The present protocol provides an atom-economical and sustainable route for the synthesis of various imine derivatives by employing an earth-abundant nickel salt and easily prepared salicylaldiminato ligands.

A Catecholaldimine-Based NiII-Complex as an Effective Catalyst for the Direct Conversion of Alcohols to trans-Cinnamonitriles and Aldehydes

“…On the basis of above findings and previous reports, ,,, a plausible mechanism for the [Ni­(HL) 2 ] 1 -catalyzed reaction for the synthesis of trans -cinnamonitrile is proposed in Scheme . Initially, the catalytic cycle begin with the reaction of KOH base with nickel complex [Ni­(HL) 2 ] 1 that generated a phenolic anionic complex ( A ), which further reacted with benzylic alcohol to give Ni II alkoxide species (II) .…”

Nickel Pincer Complexes Catalyzed Sustainable Synthesis of 3,4-Dihydro-2H-1,2,4-benzothiadiazine-1,1-dioxides via Acceptorless Dehydrogenative Coupling of Primary Alcohols

“…A plausible mechanism has been proposed by Ni­(II) pincer catalyst-mediated synthesis 3,4-dihydro-2 H -1,2,4-benzothiadiazine 1,1-dioxide ,− , (Scheme ). Initially, in the presence of the base, the benzyl alcohol reacts with the Ni­(II) catalyst ( A ) to form Ni-alkoxide species ( B ), which rapidly undertakes β-hydride elimination to afford the benzaldehyde ( C ) and Ni­(II)-hydride species ( D ).…”

Six-coordinated nickel(ii) complexes with benzothiadiazole Schiff-base ligands: synthesis, crystal structure, magnetic and HFEPR study

“…Most of the mononuclear complexes are characterized by a distorted octahedron, due to the geometry restrictions of the two tridentate ligands. A majority of the reports provided only crystallographic information, 12 some offer insights into bioactivity, 13,14 catalysis 15,16 or spectroscopic characteristics. 17 Notably, only a limited number of publications include magnetic measurements.…”