Our laboratory and others have extensively developed and exploited low-valent transition metal complexes for catalytic alkane dehydrogenation, generally with the use of a sacrificial olefinic hydrogen acceptor. Solution-phase pincer-ligated iridium complexes of the type (PCP)Ir have proven to be particularly effective. Alternative approaches to alkane dehydrogenation under investigation in our laboratory will be presented. Electrochemical oxidation of metal hydrides, and particularly proton-coupled electron transfer facilitated by metal-ligand cooperation is one such theme. Another approach, exemplified with the (Phebox)Ir(OAc)H complex first reported by Nishiyama, is based on high oxidation state intermediates; such systems are particularly amenable to acceptorless dehydrogenation. A novel approach to the development of an improved “classical” catalyst for alkane dehydrogenation is illustrated with the report of a triphosphorus (“PPP”) pincer ligand. The architecture of this ligand selectively destabilizes the resting state but not a “sideways-directed” mechanistic pathway, resulting in extremely high turnover frequencies as well as high regioselectivity for dehydrogenation of the terminal position of <i>n</i>-alkanes.

Catalytic alkane dehydrogenation: "Non-classical" approaches

ACS Spring 2022

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