C-H bond activation by organometallic catalysts allows for the efficient functionalization of petroleum feedstocks into more valuable chemical commodities. Upon activation by NaOtBu, Ir(III) CCC-pincer complexes containing meta-phenylene-bridged N-heterocyclic carbene ligands with mesityl side groups dehydrogenate linear alkanes to form alkene products, while complexes with adamantyl side groups do not. However, both catalysts efficiently isomerize terminal alkenes to form a mixture of internal alkene products, a process that hinders their ability to selectively generate the desired terminal alkene product. In an effort to better understand the influence of the ligand sterics on isomerization, the mechanism of alkene isomerization with these catalysts was investigated, including kinetic characterization of the catalysts, H-D crossover experiments, the effect of base on catalyst activity, and isolation of the catalyst resting state. Early results suggest a surprising dichotomy in the mechanism of the reaction, apparently caused by ligand steric effects.

Investigation of the influence of ligand sterics on the mechanism of alkene isomerization catalyzed by Ir(III) CCC-pincer complexes

247th National Meeting (2014)

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