Release-return metathesis, mechanism

Upon olefin coordination and the ensuing metathesis with the substrate, the catalytically active species I and a molecule of isopropoxystyrene are formed (Scheme 11.2). Once the olefin is completely consumed, rebinding of the isopropoxystyrene through release/return mechanism may reform the catalyst [34]. Therefore, it was proposed that the catalyst could be reused for several cycles. 

Vorfalt T, Wannowius KJ, Thiel V, Plenio H. How Important Is the Release-Return Mechanism in Olefin Metathesis Chem Eur J. 2010 16(41) 12312-12315. 

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