Difference Between Nitronium Nitrosonium and Nitrosyl

The key difference between nitronium nitrosonium and nitrosyl is that nitronium ion has one nitrogen atom bonded to two oxygen atoms and nitrosonium ion has one nitrogen atom bonded to one oxygen atom whereas the term nitrosyl is used when naming the nitric oxide ligand in metal complexes.

Nitronium and nitrosonium ions are inorganic ions containing nitrogen and oxygen atoms. Both these ions occur in chemical compounds as cations.

CONTENTS

1. Overview and Key Difference
2. What is Nitronium
3. What is Nitrosonium
4. What is Nitrosyl 
5. What are the Similarities Between Nitronium Nitrosonium and Nitrosyl
6. Side by Side Comparison – Nitronium vs Nitrosonium vs Nitrosyl in Tabular Form
7. Summary

What is Nitronium?

Nitronium ion is a cation having the chemical formula NO2+. We can name it as an onium ion because of its tetravalent nitrogen atom and the +1 electrical charge that is similar to the ammonium ion. This cation is created when an electron removes from the paramagnetic nitrogen dioxide molecule or through the protonation of nitric acid.

Usually, nitronium ion is stable enough to exist in normal conditions. However, this ion is generally reactive and useful extensively as an electrophile for the nitration of other substances. For this purpose, this ion is generated in situ by mixing concentrated sulfuric acid and concentrated nitric acid.

We can observe that nitronium ion is isoelectronic with carbon dioxide and nitrous oxide, and they have the same linear structure and bond angle of 180 degrees. Therefore, this ion has a similar vibrational spectrum to carbon dioxide.

There are few salts of nitronium ion where the anions are weakly nucleophilic. Examples include nitronium perchlorate (NO₂⁺ClO₄^–), nitronium tetrafluoroborate (NO₂⁺BF₄^–), nitronium hexafluorophosphate (NO₂⁺PF₆^–), nitronium hexafluoroarsenate (NO₂⁺AsF₆^–), and nitronium hexafluoroantimonate (NO₂⁺SbF₆^–).

What is Nitrosonium?

Nitrosonium is a cation having the chemical formula NO+. This cation has the nitrogen atom bonded to an oxygen atom through a triple bond. Therefore, the bond order of this molecule is 3. However, an oxygen atom can have only two chemical bonds according to its electron configuration; thus, the other chemical bond is a coordinate bond. Therefore, the overall diatomic species bears a net positive charge. This appears as nitric oxide with one electron removed.

This cation is isoelectronic with carbon monoxide (CO), cyanide anion (CN-), and nitrogen molecule (N2). We can easily get nitrosonium ion through the protonation of nitrous acid. It readily reacts with water, forming nitrous acid. Therefore, we should protect this ion from water or moist air. When this ion reacts with a base, it gives nitrile compounds. Further, nitrosonium ion can react with aryl amines as a diazotizing agent. Nitrosonium ion can act as a strong oxidizing agent as well.

What is Nitrosyl?

The term nitrosyl is used to name the nitric oxide ligand in metal complexes. The nitric oxide ligand is bonded to a central transition metal through a coordination bond. The metal complexes containing the NO ligand (nitric oxide) actually have NO+ cation which is named as nitrosyl cation (the cation derived from nitrosyl ligand).

This cation is isoelectronic with carbon monoxide. Therefore, the bonding pattern of carbon monoxide with the transition metal in carbonyl complexes is similar to that of the nitrosyl complexes.

What are the Similarities Between Nitronium Nitrosonium and Nitrosyl?

• All these ions contain nitrogen and oxygen atoms.
• These are cations having a net positive charge.
• They are oxides of nitrogen.

What is the Difference Between Nitronium Nitrosonium and Nitrosyl?

Nitronium and nitrosonium are oxide ions of nitrogen. The key difference between nitronium nitrosonium and nitrosyl is that nitronium ion has one nitrogen atom bonded to two oxygen atoms and nitrosonium ion has one nitrogen atom bonded to one oxygen atom whereas the term nitrosyl is used when naming the nitric oxide ligand in metal complexes.

Below is a summary of the difference between nitronium nitrosonium and nitrosyl in tabular form.

Summary – Nitronium vs Nitrosonium vs Nitrosyl

The key difference between nitronium nitrosonium and nitrosyl is that nitronium ion has one nitrogen atom bonded to two oxygen atoms and nitrosonium ion has one nitrogen atom bonded to one oxygen atom whereas the term nitrosyl is used when naming the nitric oxide ligand in metal complexes.

Reference:

1. “Nitronium Ion”. Libretexts. (2020, August 24). Available here.

Image Courtesy:

1. “Nitronium-2D-dimensions” (Public Domain) via Commons Wikimedia
2. “Nitrosonium-2D-dimensions” (Public Domain) via Commons Wikimedia
3. “Sodium-nitroprusside-2D” (Public Domain) via Commons Wikimedia