AbstractThe article reviews results of research that was initially aiming at complexes containing new and unusual [M—N—E] element combinations (M = transition metal, E = main group element), but soon turned into studies on model complexes for metal enzymes such as nitrogenases, hydrogenases or CO dehydrogenases, because several of the resulting [M—N—E] complexes exhibited reactions relevant to these enzymes. It could be shown that alkylation of transition metal thiolate nitride complexes gives alkylimido complexes when bulky and mild alkylation reagents, e.g. Ph3C+, are used. Hydride addition to [Ru(NO)(pybuS4)]+ yielded [Ru(HNO)(pybuS4)], which contains a bifurcated [M—N(X, Y)] bridge. The diazene complex [μ‐N2H2{Ru(PCy3)(S4)}2] undergoes H+/D+ and H+/D2 exchange reactions that enabled to rationalize the until then inexplicable ‘N2 dependent HD formation’ catalyzed by nitrogenases. Out of a larger number of [Ni(NE)(S3)] complexes, the compound [Ni(NHPPr3)(S3)] proved capable to model structure and reactivity features of [NiFe] hydrogenases. The [Ni(L)(S3)] complexes with L = N3— and N(SiMe3)2— exhibit extremely high reactivity towards CO, CO2 and SO2. The reactions lead to NCO—, CN— and NSO— complexes and bear potential relevance for carbon monoxide dehydrogenase reactions.