The pincer d(8)-monohydride complex RhH-{xant((PPr2)-Pr-i)(2)} (xant((PPr2)-Pr-i)(2) = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) promotes the release of 1 equiv of hydrogen from H3BNH3 and H3BNHMe2 with TOF50% values of 3150 and 1725 h(-1), to afford [BH2NH2](n) and [BH2NMe2](2) and the tandem ammonia borane dehydrogenation-cydohexene hydrogenation. DFT calculations on the ammonia borane dehydrogenation suggest that the process takes place by means of cis-kappa(2)-PP-species, through four stages including: (i) Shimoi-type coordination of ammonia borane, homolytic addition of the coordinated H-B bond to afford a five-coordinate dihydride-boryl-rhodium(III) intermediate, (iii) reductive intramolecular proton transfer from the NH3 group to one of the hydride ligands, and (iv) release of H-2 from the resulting square-planar hydride dihydrogen rhodium(I) intermediate.