Experimental, DFT and kinetic study of 1-octene metathesis with Hoveyda-Grubbs second generation precatalyst

In this study we report the catalytic performance, reaction engineering kinetics and elucidation of the reaction mechanism using density functional theory (OFT) for the metathesis reaction of 1-octene in the presence of the Hoveyda-Grubbs 2 [RuCl2(=CH-o-OiPrC6H4)(H(2)IMes)] precatalyst. The study showed that reaction temperature (30-100 degrees C), 1-octene/precatalyst molar ratio (5000-14,000) and different solvents had a significant effect on the selectivity, activity and turnover number. Turnover numbers as high as 6448 were observed. Two main reactions were observed, namely: metathesis over the entire temperature range and isomerization above 50 degrees C. The observed experimental product-time distribution data for the complex parallel reaction system was fairly accurately described by four pseudo-first order reaction rates. The effects of temperature (Arrhenius Equation) and precatalyst concentration were incorporated in the observed rate constant. The primary observed activation energy was approximately 24 kcal mol(-1), which is in agreement with the DFT computational values for the proposed Hoveyda-Grubbs mechanism. (C) 2011 Elsevier B.V. All rights reserved.