Pincer-iridium complexes have been reported to catalyze the dehydrogenation of alkanes and these catalyst have been combined with olefin metathesis catalysts to give a tandem catalytic system for alkane metathesis. A major challenge in dehydrogenation, and in alkane metathesis in particular, is to achieve regioselectivity for the terminal position of n-alkane substrates. We report combined computational and experimental studies which have elucidated the factors that determine the regioselectivity of dehydrogenation. In particular, we find that various pincer-iridium complexes will react with n-alkanes to initially give the 1-alkene dihydride. However, in some cases, e.g. (tBuPOCOP)Ir, the barrier to loss of olefin is high and the coordinated 1-alkene re-inserts into an Ir-H bond and ultimately gives internal olefin as a major kinetic product. We also report the rational development of pincer-iridium complexes that are more effective for alkane metathesis than the parent complexes (tBuPOCOP)Ir and (tBuPCP)Ir.

Dehydrogenation and metathesis of alkanes catalyzed by pincer-iridium complexes: Mechanistic studies and catalyst design

245th National Meeting (2013)

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