Selective B-H vs. N-H bond activation in ammonia borane by [Ir(dppm)2][OTf]

Ammonia borane (AB, NH3·BH3) was activated selectively on the boron hydrogen atoms by [Ir(dppm)2]OTf, as shown by variable-temperature 31P, 11B and 1H NMR studies, to yield cis- and trans-[Ir(H)2(dppm)2]OTf dihydrides. X-ray crystal structures of these complexes were obtained. DFT calculations suggest the key reaction intermediate to be a Lewis base (L) stabilised adduct, cis-[Ir(H)(BH2·L)(dppm)2]+