Synthesis, Structures, Electrochemistry, and Catalytic Activity towards Cyclohexanol Oxidation of Mono-, Di-, and Polynuclear Iron(III) Complexes with 3-Amino-2-Pyrazinecarboxylate

Abstract

The synthesis and characterization of a set of iron(III) complexes, viz. the mononuclear [Fe(L)3] (1) and [NHEt3][Fe(L)2(Cl)2] (2), the dinuclear methoxido-bridged [Fe(L)2(μ-OMe)]2.DMF.1.5MeOH (3), and the heteronuclear Fe(III)/Na(I) two-dimensional coordination polymer [Fe(N3)(μ-L)2(μ-O)1/2(Na)(μ-H2O)1/2]n (4), are reported. Reactions of 3-amino-2-pyrazinecarboxylic acid (HL) with iron(III) chloride under different reaction conditions were studied, and the obtained compounds were characterized by elemental analysis, Fourier Transform Infrared (FT-IR) spectroscopy, and X-ray single-crystal diffraction. Compound 1 is a neutral mononuclear complex, whereas 2 is mono-anionic with its charge being neutralized by triethylammonium cation. Compounds 3 and 4 display a di-methoxido-bridged dinuclear complex and a two-dimensional heterometallic Fe(III)/Na(I) polynuclear coordination polymer, respectively. Compounds 3 and 4 are the first examples of methoxido- and oxido-bridged iron(III) complexes, respectively, with 3-amino-2-pyrazinecarboxylate ligands. The electrochemical study of these compounds reveals a facile single-electron reversible Fe(III)-to-Fe(II) reduction at a positive potential of 0.08V vs. saturated calomel electrode (SCE), which is in line with their ability to act as efficient oxidants and heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation (with tert-butyl hydroperoxide) of cyclohexanol to cyclohexanone (almost quantitative yields after 1 h). Moreover, the catalysts are easily recovered and reused for five consecutive cycles, maintaining a high activity and selectivity.

High-Loading Single-Atom Ru Catalysts Anchored on N-Doped Graphdiyne/γ-Graphyne Quantum Dots for Selective Hydrodehalogenation and Hydrodearomatization

“…Compared to the traditional oxidation detoxification processes, selective hydrodehalogenation and hydrodearomatization of chlorophenols is considered an efficient approach for simultaneously achieving their detoxification and product reutilization . Cyclohexanol, as the final product of chlorophenols by selective hydrodehalogenation and hydrodearomatization, is a nontoxic and useful intermediate in polyamide manufacturing. , We demonstrate that GDQD-Ru/GNQD-Ru presents excellent activity for selective hydrodehalogenation and hydrodearomatization, remarkably surpassing the bulk graphdiyne/γ-graphyne-based Ru SACs (GD-Ru/GN-Ru) and Ru nanoparticles (GDN-Ru/GNN-Ru). This study will provide a novel method for the synthesis of high-loading Ru SACs using GDQDs/GNQDs and insights into their selective hydrodehalogenation and hydrodearomatization of chlorophenols into cyclohexanol.…”

Oxidation of Organic Compounds with Peroxides Catalyzed by Polynuclear Metal Compounds

“…In works [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] 4. ; 1-(bis-pyridin-2-ylmethylamino)-3-chloropropan-2-ol (L) have been described [21].…”

“…It cannot be ruled out that the mononuclear complex in solution forms polynuclear particles that are involved in the oxidation of alkane. Other compounds appearing on the oxidation of organic compounds with peroxides catalyzed by polynuclear iron derivatives have been also published in works [27][28][29][30][31][32][33][34][35][36].…”