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 11/24/2018 Reaction Types

Less Common Reaction Types Hapticity changes Single-electron oxidation/reduction Bond homolysis Electrocyclic reactions 11/24/2018 Reaction Types

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". 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types

Bond homolysis Requires a weak M-C bond Typically for: heavier main-group metals first-row transition metals in high oxidation states 11/24/2018 Reaction Types

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 11/24/2018 Reaction Types