Forming a ruthenium isomerisation catalyst from Grubbs II: a DFT study

Area of Science:

• Organometallic Chemistry
• Catalysis
• Computational Chemistry

Background:

• Grubbs 2nd generation pre-catalyst is widely used in olefin metathesis.
• Understanding pre-catalyst decomposition is crucial for optimizing catalytic reactions.
• Methanol can act as a ligand or reactant in organometallic systems.

Purpose of the Study:

• To elucidate the decomposition mechanism of Grubbs 2nd generation pre-catalyst (2) in methanol.
• To compare the energetic favorability of different decomposition pathways.
• To identify potential competing reaction pathways.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Gibbs free energy profiles were computed for proposed decomposition mechanisms.
• The influence of methanol on the pre-catalyst stability was investigated.

Main Results:

• Two distinct decomposition mechanisms were analyzed computationally.
• Decomposition via tricyclohexylphosphane dissociation was predicted as the most energetically favorable pathway.
• Ruthenium hydride formation was identified as a potentially competitive pathway depending on reaction conditions.

Conclusions:

• The tricyclohexylphosphane dissociation pathway is the dominant decomposition route for Grubbs 2nd generation pre-catalyst in methanol.
• Reaction conditions can influence the prevalence of ruthenium hydride formation.
• This mechanistic insight aids in the rational design and application of Grubbs catalysts.