User:Parkr91/sandbox

'''Tolman's Rule '''

Tolman's rule states that in a reaction, the steps that the reaction goes through involve only of 18 electron complex and 16 electron complex variants. In these organometallic reactions, an alternation between the 18 electron and 16 electron complexes are seen. Homogeneous organometallic catalysis usually follow this rule. This rule was made by Dr. Chadwick A. Tolman.

To further elaborate, if a certain species has 16 valence electrons, then that complex would most likely become an 18 electron electron species if it went through an organometallic reaction. However, if a species with 18 valence electrons goes through an organometallic reaction, then the complex most likely would become a 16 valence electron species. It should be noted that 18 valence electron species has a greater chance of retaining its number of valence electrons than a 16 valence electron species.

The reason why many organometallic compounds achieve a 16 or 18 electron valence electron configuration is due to stability. Having 16 or 18 electron states are most energetically stable for these compounds. 16 electron configurations structures are square-planar, whereas 18 electron configuration structures are octahedral. A general trend that we see is that column 3, 4, and 5 d-orbital metals usually have fewer than 18 electrons, column 6, 7, and 8 d-orbital metals usually have 18 electrons, and column 9 and 10 d-orbital metals usually have 16 or 18 electrons.

'''16 electron species reactions '''

Lewis Base Associations

A ligand that acts as a lewis base attaches to the transition metal complex.

Example: trans-RPtCl(PPh3)2 + py --> RPtCl(PPh3)2py

Oxidative Addition

A ligand attaches to a metal complex, leading to an oxidation and coordination number increase of the metal center.

Example: CH3I + cis-[Rh(CO)2I2]− --> [(CH3)Rh(CO)2I3]−

De-Insertions

Opposite of an insertion reaction. A ligand that was attached to a ligand-metal bond forms a new bond to the same metal complex.

Example: Mn(CO)4(13CO)COCH3 --> Mn(CO)5CH3 + 13CO

18 electron species reactions

Lewis Base Dissociations

A ligand that acts as a lewis base detaches from the transition metal complex.

RPtCl(PPh3)2py --> Cl- + trans-RPt(PPh3)2py

Reductive Eliminations

A ligand leaves a metal complex, leading to an oxidation and coordination number decrease of the metal center.

Example: [CH3CORhI3(CO)2]- --> CH3COI + [RhI2(CO)2]-

Migratory Insertions

Two ligands on the same metal complex form a bond.

Example: 13CO + Mn(CO)5CH3 --> Mn(CO)4(13CO)COCH3

Oxidative Couplings

An oxidative reaction is used to combine two two molecules.

Example: ArB(OMe)2 +MeOH +1/2 O2 --> Ar-OMe + (HO)B(OMe)2

References