The key difference between oxidative addition and reductive elimination is that oxidative addition refers to the addition of two anionic ligands to a metal complex, whereas reductive elimination refers to the removal of two anionic ligands from a metal complex.
Oxidative addition and reductive elimination are chemical reactions that are opposite to each other. These two processes are related to coordination complexes that contain a transition metal and ligands attached to it.
CONTENTS
1. Overview and Key Difference
2. What is Oxidative Addition
3. What is Reductive Elimination
4. Side by Side Comparison – Oxidative Addition vs Reductive Elimination in Tabular Form
5. Summary
What is Oxidative Addition
Oxidative addition is a type of inorganic reaction in which two anionic ligands are attached to a coordination complex. We can denote this process as OA. Here, the anionic ligands usually form from A-B type molecules. The exact reverse process of this reaction – where two anionic ligands leave the coordination complex forming an A-B type molecule – is known as reductive elimination. Since this reaction involves an increase in the number of ligands in the coordination complex, the coordination number also increases with oxidative addition. Therefore, the valence electron count of the complex also increases by two units. For this type of reaction to occur, the coordination complex should be unsaturated or electron-deficient.
Figure 01: A General Sketch for Oxidative Addition
Generally, oxidative addition transforms a 16-valence electron coordination complex into an 18-valence electron complex. Furthermore, oxidative addition can occur as a binuclear oxidative addition. Here, two metal centres undergo oxidation state changes, and their oxidation states increase by one unit, which gives a total of two-unit increment.
What is Reductive Elimination?
Reductive elimination is the removal of two anionic ligands from a metal complex, which is the complete opposite of the oxidative addition reaction. This process reduces the formal oxidation state of the metal of the coordination complex, and the coordination number reduces by two units.
Figure 02: A General Sketch for Reductive Elimination
We can observe this type of reactions in coordination complexes containing metals having d6 and d8 electron systems. This type of reactions can occur by conversion of 18-valence electron complexes into 16-valence electron complexes and via binuclear elimination reactions. In the binuclear elimination reaction, two metal complexes reduce their formal oxidation states by one unit and give a two-unit reduction of formal oxidation state and valence electron count.
What is the Difference Between Oxidative Addition and Reductive Elimination?
Oxidative addition and reductive elimination are reactions opposite to each other. The key difference between oxidative addition and reductive elimination is that oxidative addition refers to the addition of two anionic ligands to a metal complex, whereas reductive elimination refers to the removal of two anionic ligands from a metal complex. Moreover, in oxidative addition, the valence electron count and the formal oxidation state increases by two units, but in reductive elimination reaction, the formal oxidation state and valence electron count decrease by two units.
Below is a detailed description of the difference between oxidative addition and reductive elimination.
Summary – Oxidative Addition vs Reductive Elimination
Oxidative addition and reductive elimination are chemical reactions that are opposite to each other. The key difference between oxidative addition and reductive elimination is that oxidative addition refers to the addition of two anionic ligands to a metal complex, whereas reductive elimination refers to the removal of two anionic ligands from a metal complex.
Reference:
1.“10.1: Oxidative Addition and Reductive Elimination.” Chemistry LibreTexts, Libretexts, 13 Oct. 2019, Available here.
2. “5.5: Oxidative Addition.” Chemistry LibreTexts, Libretexts, 5 June 2019, Available here.
3. “Oxidative Addition.” Wikipedia, Wikimedia Foundation, 9 Nov. 2019, Available here.
4. “Reductive Elimination: General Ideas.” Chemistry LibreTexts, Libretexts, 5 June 2019, Available here.
Image Courtesy:
1. “Concerted OA” By Rifleman 82 (talk) – Rifleman 82 (talk) (Public Domain) via Commons Wikimedia
2. “Reductive Elimination Bite Angles” By Jgurak – Own work (CC BY-SA 4.0) via Commons Wikimedia