Water-Accelerated Decomposition of Olefin Metathesis Catalysts
Christian O. Blanco, Deryn E. Fogg
Abstract
High Resolution Image Download MS PowerPoint Slide Water is ubiquitous in olefin metathesis, at levels ranging from contaminant to cosolvent. It is also non-benign. Water-promoted catalyst decomposition competes with metathesis, even for “robust” ruthenium catalysts. Metathesis is hence typically noncatalytic for demanding reactions in water-rich environments (e.g., chemical biology), a challenge as the Ru decomposition products promote unwanted reactions such as DNA degradation. To date, only the first step of the decomposition cascade is understood: catalyst aquation. Here we demonstrate that the aqua species dramatically accelerate both β-elimination of the metallacyclobutane intermediate and bimolecular decomposition of four-coordinate [RuCl(H 2 O) n (L)(═CHR)]Cl. Decomposition can be inhibited by blocking aquation and β-elimination.