Synthesis of phase pure Co3Mo3N and Fe3Mo3N by temperature programmed ammonolysis has been established by XRD and elemental analysis. The ternary nitrides are characterised by a eta-6 structure and low surface area (4-9 m(2) g(-1)). Pseudomorphic transformation of cobalt molybdate prepared using cobalt nitrate generated rod-shaped crystals while the use of iron chloride resulted in Fe3Mo3N aggregates with irregular morphology and wide size distribution. XPS measurements have revealed surface N enrichment relative to the bulk where the passivated samples show a range of oxidation states; Co3Mo3N exhibited Mo2+ and Con+ (0 <= n <= 3) whereas Fe3Mo3N was characterised by higher oxidation states (Fe3+ and Mo3+). Temperature programmed reduction (TPR) to 823 K served to remove the passivation layer where subsequent H-2 chemisorption and temperature programmed desorption (TPD) has demonstrated greater uptake on Fe3Mo3N relative to Co3Mo3N, resulting in a higher nitrobenzene hydrogenation rate (to aniline). Fe3Mo3N promoted selective reduction of -NO2 in p-chloronitrobenzene to generate p-chloroaniline as sole product whereas Co3Mo3N favoured C-Cl scission with the formation of nitrobenzene (in addition to p-chloroaniline). Hydrodechlorination properties were further established for Co3Mo3N in the conversion of chlorobenzene (to benzene) under conditions where Fe3Mo3N was inactive. A temporal deactivation of both nitrides is associated with Cl poisoning of Co3Mo3N and structural changes to Fe3Mo3N. (C) 2014 Elsevier B.V. All rights reserved.