Homogeneous Ta/Ir tandem catalytic alkane/alkene coupling

Abstract

Light alkanes and alkenes are abundant but under-utilized energy carriers due to their high volatility and low energy d. A tandem catalytic approach for the coupling of alkanes and alkenes has been developed in order to upgrade these light hydrocarbons into heavier fuel mols. This process involves alkane dehydrogenation by pincer- ligated iridium complexes, and alkene dimerization by a Cp*TaCl_2(alkene) catalyst. These two homogeneous catalysts operate with up to 60 /30 cooperative turnovers (Ir/Ta) in the dimerization of 1- hexene /n- heptane, giving C_(13)/C_(14) products in 40 % yield. Because there is no kinetically relevant interaction between the two catalysts, the tandem mechanism can be entirely described using the two independent catalytic cycles. A nickel dimerization catalyst produces largely linear dimers, unlike the tantalum dimerization catalyst that produces gem- substituted dimers. Attempts to realize a truly catalytic Ni/Ir version that produces only a C_(2n) alkane from a C_n olefin and C_n alkane feed will be described.