Kinetic Modelling of Cobalt-Catalyzed Propene Hydroformylation: A Combined Ab Initio and Experimental Fitting Protocol

Kinetic modelling of catalytic reaction systems can yield detailed insight into mechanisms, enabling in particular the identification of rate- and turnover-limiting steps. Empirical models fitted to observed kinetics do not always unambiguously resolve the microscopic nature of the mechanism, while ab initio models with rate constants derived from statistical rate theories and quantum chemistry invariably lead to mismatches between predicted and observed rates, sometimes even to the extent that the dependence of the rate on key variables such as temperature or concentration is incorrect. We have shown previously that when using accurate quantum chemical methods, agreement with experiment of ab initio kinetic models can be good, and can be further improved by performing limited fitting of the ab initio values. Here we show that a detailed assessment of the remaining mismatches with experiment combined with a careful fitting protocol and with additional quantum chemical calculations can yield much improved accuracy and improved microscopic understanding of the reaction mechanism, for the important test case of propene hydroformylation by Co2(CO)8.