Homolytic N–H Activation of Ammonia: Hydrogen Transfer of Parent Iridium Ammine, Amide, Imide, and Nitride Species

The redox series [Ir(n)(NHx)(PNP)] (n = II-IV, x = 3-0; PNP = N(CHCHPtBu2)2) was examined with respect to electron, proton, and hydrogen atom transfer steps. The experimental and computational results suggest that the Ir(III) imido species [Ir(NH)(PNP)] is not stable but undergoes disproportionation to the respective Ir(II) amido and Ir(IV) nitrido species. N-H bond strengths are estimated upon reaction with hydrogen atom transfer reagents to rationalize this observation and are used to discuss the reactivity of these compounds toward E-H bond activation.