Regioselective Gas‐Phase n ‐Butane Transfer Dehydrogenation via Silica‐Supported Pincer‐Iridium Complexes

The production of olefins via on‐purpose dehydrogenation of alkanes allows for a more efficient, selective and lower cost alternative to processes such as steam cracking. Silica‐supported pincer‐iridium complexes of the form [(≡SiO− R4 POCOP)Ir(CO)] ( R4 POCOP=κ 3 ‐C 6 H 3 ‐2,6‐(OPR 2 ) 2 ) are effective for acceptorless alkane dehydrogenation, and have been shown stable up to 300 °C. However, while solution‐phase analogues of such species have demonstrated high regioselectivity for terminal olefin production under transfer dehydrogenation conditions at or below 240 °C, in open systems at 300 °C, regioselectivity under acceptorless dehydrogenation conditions is consistently low. In this work, complexes [(≡SiO− t Bu4 POCOP)Ir(CO)] ( 1 ) and [(≡SiO− i Pr4 PCP)Ir(CO)] ( 2 ) were synthesized via immobilization of molecular precursors. These complexes were used for gas‐phase butane transfer dehydrogenation using increasingly sterically demanding olefins, resulting in observed selectivities of up to 77 %. The results indicate that the active site is conserved upon immobilization.