Evidence for Reversible Cyclometalation in Alkane Dehydrogenation and C–O Bond Cleavage at Iridium Bis(phosphine) Complexes

Methyl tert-butyl ether is found to undergo C–O bond cleavage in the formation of an iridium­(III) methallyl at a cationic bis­(phosphine) iridium complex. An exploration of this transformation has revealed a cyclometalated complex which was previously postulated to form reversibly in the first example of alkane dehydrogenation by a homogeneous transition-metal complex. The competence of this cyclometalated species in alkane dehydrogenation is demonstrated in a stoichiometric example, giving an isolable olefin dihydride. Detection and assignment of this elusive species confirms a previous hypothesis that reversible intramolecular phosphine cyclometalation can precede intermolecular alkane dehydrogenation.