From [M≡N] and [M—N—E] Complexes to Models for Metal Oxidoreductases

The 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. Ph 3 C + , are used. Hydride addition to [Ru(NO)(py bu S 4 )] + yielded [Ru(HNO)(py bu S 4 )], which contains a bifurcated [M—N(X, Y)] bridge. The diazene complex [μ‐N 2 H 2 {Ru(PCy 3 )(S 4 )} 2 ] undergoes H + /D + and H + /D 2 exchange reactions that enabled to rationalize the until then inexplicable ‘N 2 dependent HD formation’ catalyzed by nitrogenases. Out of a larger number of [Ni(NE)(S 3 )] complexes, the compound [Ni(NHPPr 3 )(S 3 )] proved capable to model structure and reactivity features of [NiFe] hydrogenases. The [Ni(L)(S 3 )] complexes with L = N 3 — and N(SiMe 3 ) 2 — exhibit extremely high reactivity towards CO, CO 2 and SO 2 . The reactions lead to NCO — , CN — and NSO — complexes and bear potential relevance for carbon monoxide dehydrogenase reactions.