Our studies focus on the use of Co3Mo3N (331) as a catalyst in ammonia synthesis. During synthesis, N is lost and the compound is transformed to the new nitride Co6Mo6N (661); a reversible process. This process has wide implications in the development of new catalysts for N transfer reactions. The aim here is to develop definitive models for the 331 and 661 nitrides both pre- and post- gas treatments. XRD suggests that N migrates between crystallographic sites as it is lost/regained and is therefore mobile. Further, the removal of N has subtle but significant effects on the magnetism of the system. We will probe, in parallel, LiMoN2 which demonstrates similar catalytic activity, but much more subtle structural changes. A simultaneous application for TOSCA time is being made to develop an underpinning understanding of the mechanism of the processes.