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Solvent effects on Grubbs' pre-catalyst initiation rates.

Ian W Ashworth¹, David J Nelson, Jonathan M Percy

¹Global Research and Development, AstraZeneca, Silk Road Business Park, Charter Way, Macclesfield, SK10 2NA, UK.

Dalton Transactions (Cambridge, England : 2003)

|November 28, 2012

Summary

This summary is machine-generated.

Accurate initiation rates for Grubbs and Grubbs-Hoveyda second-generation pre-catalysts were measured across various solvents. Different solvent parameter dependencies suggest distinct initiation mechanisms for these important olefin metathesis catalysts.

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Area of Science:

Organometallic Chemistry
Catalysis
Polymer Science

Background:

Olefin metathesis is a vital reaction in organic synthesis and polymer chemistry.
Grubbs and Grubbs-Hoveyda second-generation pre-catalysts are widely used due to their efficiency and stability.
Understanding pre-catalyst initiation is crucial for optimizing reaction conditions and predicting outcomes.

Purpose of the Study:

To accurately quantify the initiation rates of Grubbs and Grubbs-Hoveyda second-generation pre-catalysts.
To investigate the influence of solvent properties on pre-catalyst initiation.
To elucidate the mechanistic differences between the initiation pathways of the two pre-catalysts.

Main Methods:

Kinetic studies were performed to measure initiation rates in various solvents.
Solvatochromic analysis was employed to correlate initiation rates with solvent parameters.
Comparative analysis of kinetic data and solvent effects for both pre-catalysts.

Main Results:

Initiation rates varied significantly depending on the solvent environment for both pre-catalysts.
Solvatochromic fitting revealed distinct dependencies on solvent polarity and other parameters for Grubbs and Grubbs-Hoveyda pre-catalysts.
The observed differences in solvent dependency support divergent initiation mechanisms.

Conclusions:

The initiation mechanisms of Grubbs and Grubbs-Hoveyda second-generation pre-catalysts are demonstrably different.
Solvent choice plays a critical role in modulating the initiation kinetics of these catalysts.
This study provides valuable insights for the rational selection of solvents in olefin metathesis reactions.