Catalytic Alkane Metathesis by Tandem Alkane Dehydrogenation-Olefin Metathesis

With petroleum supplies dwindling, there is increasing interest in selective methods for transforming other carbon feedstocks into hydrocarbons suitable for transportation fuel. We report the development of highly productive, well-defined, tandem catalytic systems for the metathesis of n-alkanes. Each system comprises one molecular catalyst (a "pincer"-ligated iridium complex) that effects alkane dehydrogenation and olefin hydrogenation, plus a second catalyst (molecular or solid-phase) for olefin metathesis. The systems all show complete selectivity for linear (n-alkane) product. We report one example that achieves selectivity with respect to the distribution of product molecular weights, in which n-decane is the predominant high-molecular-weight product of the metathesis of two moles of n-hexane.