Hydrogenation of the (PONOP)Ir(I)CH3 complex [PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine] yields the unexpected trans-dihydride species (PONOP)IICH3(H)(2). Mechanistic investigations have revealed that this reaction proceeds via proton-catalyzed H-2 cleavage, a pathway that circumvents the intermediacy of the typically invoked cis-dihydride isomer. Protonation yields the cationic (PONOP)Ir(CH3)(H). complex, which is then trapped by H-2 to yield an eta(2)-H-2 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.