A Highly Stable Adamantyl-Substituted Pincer-Ligated Iridium Catalyst for Alkane Dehydrogenation

The adamantyl-substituted pincer-ligand precursor Ad PCP-H [( Ad PCP = κ 3 -C 6 H 3 -2,6-(CH 2 PAd 2 ) 2 ); Ad = 1-adamantyl] has been synthesized by the reaction of 1,3-dibromoxylene with di-1-adamantylphosphine in the presence of triethylamine. Treatment of Ad PCP-H with [Ir(COD)Cl] 2 (COD = 1,5-cyclooctadiene) affords the pincer-ligated complex ( Ad PCP)IrHCl, which was crystallographically characterized. Dehydrohalogenation of ( Ad PCP)IrHCl either with LiBEt 3 H or with KO t Bu, under hydrogen atmosphere, yields the hydrides ( Ad PCP)IrH 2 and ( Ad PCP)IrH 4 . ( Ad PCP)IrH 2 catalyzes dehydrogenation of alkanes with a level of activity comparable to that of the previously reported ( tBu PCP)IrH 2, while it is thermally much more robust than the tBu PCP analogue, as well as iPr PCP or tBu POCOP pincer complexes.