<b>Abstract:</b> 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-<sup>R4</sup>POCOP)Ir(CO)] (<sup>R4</sup>POCOP
= κ<sup>3</sup>-C<sub>6</sub>H<sub>3</sub>-2,6-(OPR<sub>2</sub>)<sub>2</sub>)
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 <a>[(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)Ir(CO)]
</a>(<b>1</b>) and [(≡SiO-<i><sup>i</sup></i><sup>Pr4</sup>PCP)Ir(CO)] (<b>2</b>) 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.
