Hydrogenation of the (PONOP)Ir(I)CH3 complex [PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine] yields the unexpected trans-dihydride species (PONOP)IrCH3(H)2. Mechanistic investigations have revealed that this reaction proceeds via proton-catalyzed H2 cleavage, a pathway that circumvents the intermediacy of the typically invoked cis-dihydride isomer. Protonation yields the cationic (PONOP)Ir(CH 3)(H)+ complex, which is then trapped by H2 to yield an η2-H2 complex. Deprotonation of this species yields the trans-dihydride. Intermediates in the proposed pathway have been confirmed by independent low-temperature syntheses and spectroscopic observations.