Ammonia borane (AB) is an interesting candidate for chemical hydrogen storage. The complex (POCOP)IrH2 (POCOP = η3-(1,3-OPtBu2)2C6H3) has been shown to be an efficient catalyst for H2 release from AB. Under low H2 pressure a dormant form of the catalyst appears, subsequently identified as (POCOP)Ir(H)2(BH3). This interesting s-bonded BH3 complex has been investigated by a variety of spectroscopic methods, including neutron diffraction analysis. During the course of AB dehydrogenation, the predominant Ir-containing species present in solution is (POCOP)IrH4. The structure of this complex has been investigated using a variety of NMR techniques and IR spectroscopy. We have also studied the structure of the closely related complex (PCP)IrH4 (PCP = η3-(1,3-CH2PtBu2)2C6H3)in solution. The resulting solution data reveal a different arrangement of H atoms around the Ir than a solid-state structure obtained by neutron diffraction analysis.