In order to elucidate the reaction pathways in complex hydrogen storage materials, the compound KMg(NH)(NH2) was synthesized from the reversible dehydrogenation process of a Mg(NH2)2/KH mixture. Preliminary powder X-ray diffraction patterns on specimens without any deuteration were supplemented with neutron powder diffraction studies on the reaction products from deuterated precursors with the intent of solving the crystal structure. The compound presents the orthorhombic space group Pnma (62) with lattice parameters: a = 9.3497(3)Å; b = 3,6631(1)Å; c = 9.8901(3)Å, respectively. The coexistence of imide/amide groups in the same compound allows us to notice for the fi rst time a heptahedral geometry arrangement around potassium atoms by imide and amide units. ; JRC.F.2-Energy Conversion and Storage Technologies