Abstract
DFT calculations have been used to determine the thermodynamic and kinetic preference for ruthenacyclobutanes resulting from the experimentally proposed interconversion pathways (olefin and alkylidene rotations) through the investigation of cross-metathesis reaction mechanism for neutral Grubbs catalyst, RuCl2(=CHEt)NHC (A), with ethylene and 1-butene as the substrates. Our results show that although the proposed interconversions are feasible due to the predicted low energy barriers (2-6 kcal/mol), the formation of ruthenacyclobutane is kinetically favored over the competitive reactions involving alkylidene rotations. In comparison with catalyst A, the reaction energy profile for cationic Piers catalyst [RuCl2(=CHPCy3)NHC+] (B) is more endothermic in nature with both ethylene and 1-butene substrates.
A.P. thanks the Spanish MINECO for a Ramon y Cajal contract (RYC-2009-05226) and a Jose Castillejo fellowship (CAS14/00165), and European Commission for a Career Integration Grant (CIG09-GA-2011-293900).