Ammonia-borane dehydrogenation mediated by transition metal complexes for H2 storage and production

Chemical hydrogen storage with small lightweight and hydrogen-rich molecules like ammonia-borane (NH3?BH3, AB, 19.3 wt.% H2) or amino boranes of general formula RNH2?BH3 (R = alifatic chain or cycle) is a topic of great interest, as witnessed by the exponential growth of the number of papers published in the recent literature. Transition metal complexes can catalyze H2 release from these species under mild conditions and offer great potential as H-storage materials. The reactions of assorted Co(I), Ir(I), Pd(II) and Ru(II) polyphosphine (Figure 1) and pincer type complexes with AB and amine boranes have been analyzed experimentally through variable-temperaure multinuclear (11B, 31P, 1H) NMR spectroscopy, kinetic rate measurements and kinetic isotope effect (KIE) determination with deuterated isotopologues. At the same time, a DFT modeling of the reaction mechanisms has been carried out, starting from the experimental data available. The results will be presented.