The decomposition route of N-substituted calcium amidoborane complexes depends on the steric bulk of the substituent. Relatively small substituents (R = H, Me, iPr) gave dehydrogenation to dimeric complexes with a bridging RN-BH-N(R)-BH32- ion, whereas the larger 2,6-di-isopropylphenyt substituent resulted in formation of a complex with a borylamide anion: H2B(R)N-. This product is a promising species for (catatytic) regeneration with H-2, i.e., hydrogenation to the amidoborane anion H3B(R)NH-.