1. Standard Organometallic Reaction Types
Ligand dissociation/association
Insertion/elimination
Oxidative addition/reductive elimination
s-bond metathesis
Isomerization
Nucleophilic or electrophilic attack at metal
Nucleophilic or electrophilic attack at ligand
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Reaction Types

2. Less Common Reaction Types
Hapticity changes
Single-electron oxidation/reduction
Bond homolysis
Electrocyclic reactions
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Reaction Types

3. What else is there?
Most organometallic reactions can be written in terms of series of these standard reactions.
Whether they really go like that is not always certain.
When looking for an acceptable mechanism, try to restrict yourself to the "standard steps".
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Reaction Types

4. Ligand dissociation/association
Electron count changes by -/+ 2
No change in oxidation state
Dissociation easiest if ligand stable on its own
(CO, olefin, phosphine, Cl-, ...)
Steric factors important
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Reaction Types

5. Insertion/elimination
Migratory insertion!
The ligands involved must be cis.
Electron count changes by -/+ 2
No change in oxidation state
Olefins: 1,2-insertion, b-elimination
CO, RNC: 1,1-insertion, a-elimination
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Reaction Types

6. Oxidative addition/ reductive elimination
Electron count changes by +/- 2 (assuming the reactant was not yet coordinated)
Oxidation state changes by +/- 2
Mechanism may be complicated
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Reaction Types

7. s-bond metathesis Requires an empty site
Electron count does not change
Oxidation state does not change
Can often be viewed as an acid-base reaction
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Reaction Types

8. Isomerization Movement of ligands around the metal
No change in electron count, oxidation state
Common for 3- and 5-coordinate species, less usual for 4-coordinate complexes, hardly ever for 6-coordinate octahedral complexes
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Reaction Types

9. Nucleophilic or electrophilic attack at metal
requires an empty site
is basically ligand association
Electrophilic:
requires a metal-centered lone pair
no change in electron count
usually +2 in oxidation state
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Reaction Types

10. Nucleophilic or electrophilic attack at ligand
requires an electron-poor ligand atom (acidic proton, coordinated C=X bond)
Electrophilic:
requires a ligand-centered electron pair (usually a lone pair, ligand p-bond, or M-C s-bond)
often reduces electron count by 2
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Reaction Types

11. Hapticity changes Often indenyl, dienes; sometimes for Cp
Changes electron count
Does not change oxidation state
Is usually a way for a system to "make room" for another reaction or to avoid counts above 18-e
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Reaction Types

12. Single-electron oxidation/reduction
Changes both electron count and oxidation state by 1
Usually by an added oxidant/reductant or electrochemically
Oxidized and reduced species typically differ widely in reactivity
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Reaction Types

13. Bond homolysis Requires a weak M-C bond Typically for:
heavier main-group metals
first-row transition metals in high oxidation states
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Reaction Types

14. Electrocyclic reactions
Can often be written as insertions or oxidative additions
Most common for complexes bearing two coordinated alkenes or alkynes and in olefin metathesis
Usually change both electron count and oxidation state
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Reaction Types