Exploring the reactivity of Ru-based metathesis catalysts with a pi-acid ligand trans to the Ru-ylidene bond.
In this work we explore the reactivity induced by coordination of a CO molecule trans to the Ru-ylidene bond of a prototype Ru-olefin metathesis catalyst bearing the N-heterocyclic carbene (NHC) ligand SIMes. Static DFT calculations indicate that CO binding to the Ru center promotes a cascade of reactions with very low energy barriers that lead to the final crystallographically characterized product, in which the original methylidene group has attacked the proximal aromatic ring of the SIMes ligand leading to a cycloheptatriene through a Buchner ring expansion. Analysis of the relevant molecular orbitals, supported by ab initio molecular dynamics simulations, illuminate the key role of the pi-acid CO coordinated trans to the Ru-methylidene bond to promote this reactivity. Based on this result, we investigated to which extent a large set of pi-acid groups could promote this deactivating reaction. Results clearly indicate that almost any sufficiently pi-acidic group that can approach the Ru center in the sterically crowded position trans to the Ru-methylidene bond can promote this deactivation route.
Poater
Albert
A
Modeling Lab for Nanostructures and Catalysis, Dipartimento di Chimica, Università di Salerno, Via Ponte don Melillo, I-84084 Fisciano (SA), Italy.
Ragone
Francesco
F
Correa
Andrea
A
Cavallo
Luigi
L