Migratory insertion

A migratory insertion is a type of reaction in organometallic chemistry, where a cisoidal anion and a neutal ligand on a metal complex join together resulting in a coordinated anion ligand.

Introduction

Migratory insertion is a reaction in which an anion ligand and a neutral ligand (on a metal) couple and generate a new anionic ligand. The anion and neutral ligands that react are cisoidal to one another. When an anion and a neutral react, they leave an empty metal orbital. An incoming ligand can react with the metal’s empty orbital. The anion ligand can be: H⁻ (hydride), R⁻ (alkyl), acyl, Ar⁻ (aryl), or O²⁻ (oxo). The neutral ligand can be: CO, alkenes, alkynes, or carbenes.

Mechanisms

There are two different reactions that can occur during migratory insertion. One is when the anionic ligand attacks the electrophilic part of the neutral ligand (the anionic ligand migrates to the neutral ligand). The other is when the neutral ligand inserts itself between the metal and the anionic ligand. Both mechanisms are possible. In general, it doesn’t matter if the neutral ligand inserts or if the anionic ligand migrates.

Alkene Migratory Insertion

Alkene and hydride migratory insertion is very important for polymerization catalysts. Polymerization catalysts turn alkenes into an alkyl chain. With the addition of more alkenes, a catalyst can make a polymer ^[1] .

Mechanism

The mechanism for alkene and hydride migratory insertion is shown below. First the alkene binds to the metal hydride. Next, electrons shift so the hydrogen on the metal is also bound to the alkene. Lastly, electrons shift to form an alkane and leave the metal with an empty orbital. The metal can bind to a new alkene where the empty orbital is.

External links

• Migratory Insertion]
• The Organometallic HyperTextBook: Insertion Reactions
• migratory insertion

References