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Related Concept Videos

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism01:37

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism

3.8K
Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.
3.8K
Formation of Complex Ions03:45

Formation of Complex Ions

23.6K
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
23.6K
Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions01:20

Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions

1.9K
Arenediazonium substitution reactions occur when the diazonium group is substituted by various functional groups such as halides, hydroxyl, nitrile, etc. For instance, arenediazonium salts react with copper(I) salts of chloride, bromide, or cyanide to form corresponding aryl chlorides, bromides, and nitriles. These reactions are named Sandmeyer reactions. Although the mechanism of this reaction is complicated, as illustrated in Figure 1, they are believed to progress via an aryl copper...
1.9K
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview01:26

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview

3.3K
Nitrous acid and nitric acids are two types of acids containing nitrogen, among which nitrous acid is weaker than nitric acid. Nitrous acid with a pKa value of 3.37 ionizes in water to give a nitrite ion and the hydronium ion.
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by...
3.3K
Diazonium Group Substitution: –OH and –H01:19

Diazonium Group Substitution: –OH and –H

2.8K
Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.
2.8K
Aryldiazonium Salts to Azo Dyes: Diazo Coupling01:11

Aryldiazonium Salts to Azo Dyes: Diazo Coupling

2.9K
The reaction of weakly electrophilic aryldiazonium (also called arenediazonium) salts with highly activated aromatic compounds leads to the formation of products with an —N=N— link, called an azo linkage. This reaction, presented in Figure 1, is known as diazo coupling and occurs without the loss of the nitrogen atoms of the aryldiazonium salt. Highly activated aromatic compounds such as phenols or arylamines favor the diazo coupling reaction. The coupling generally occurs at the...
2.9K

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Thermochemical Studies of NiII and ZnII Ternary Complexes Using Ion Mobility-Mass Spectrometry
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Evaluating Diazene to N2 Interconversion at Iron-Sulfur Complexes.

Reagan X Hooper1, Ashlee E Wertz2, Hannah S Shafaat2,3

  • 1Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT-06511.

Chemistry (Weinheim an Der Bergstrasse, Germany)
|February 20, 2024
PubMed
Summary

Synthetic diiron complexes do not mimic biological nitrogen fixation via proton-coupled electron transfer (PCET). The studied complex forms a mononuclear iron(III) diazene, not a dinitrogen complex, due to high PCET barriers.

Keywords:
diazeneironnitrogennitrogenaseproton-coupled electron transfer

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Area of Science:

  • Bioinorganic chemistry
  • Organometallic chemistry
  • Nitrogen fixation research

Background:

  • Biological nitrogen (N₂) reduction occurs at sulfur-rich multi-iron sites.
  • A proposed pathway involves concerted double reduction/protonation of bridging N₂ via proton-coupled electron transfer (PCET).
  • Synthetic sulfur-supported diiron complexes are explored as mimics for this biological process.

Purpose of the Study:

  • To test the feasibility of synthetic sulfur-supported diiron complexes mimicking the biological N₂ fixation pathway.
  • To investigate the energetics of the microscopic reverse of N₂ fixation: oxidative proton transfer from diazene.
  • To determine the structure and energetics of the product formed from the oxidation of a diiron-diazene complex.

Main Methods:

  • Resonance Raman spectroscopy
  • Mössbauer spectroscopy
  • Nuclear Magnetic Resonance (NMR) spectroscopy
  • Electron Paramagnetic Resonance (EPR) spectroscopy
  • Density Functional Theory (DFT) calculations

Main Results:

  • The product of oxidation was determined not to be a dinitrogen complex as previously assigned.
  • Spectroscopic and computational data indicate the formation of a mononuclear iron(III) diazene complex.
  • Calculations reveal a prohibitively high barrier for the proposed double PCET pathway at the reaction temperature.
  • PCET from bridging diazene is highly exergonic, making the reverse N₂ protonation endergonic.

Conclusions:

  • Synthetic diiron complexes studied do not replicate the proposed biological N₂ fixation pathway via PCET.
  • The high redox potential of the iron sites favors diazene oxidation, hindering N₂ protonation.
  • This work establishes "ground rules" for designing reversible N₂/N₂H₂ interconversion systems by tuning metal site redox potentials.