Fig. 2. Select previously reported systems incorporating hydrogen-bonding or proton-responsive ligands for the binding and/or conversion of nitrogenous substrates. (a) Treatment of a Cr(0)–(N2)2 complex within a scaffold bearing tertiary amines with acid produces ammonia and hydrazine. 13a (b) The participation of a proton-responsive ligand is invoked in the disproportionation of hydrazine by Fe(ii). 14 (c) Fe(ii) and Fe(iii) complexes of ammonia show multiple hydrogen-bonding interactions with ligand. 16 .
