Dinitrogen binding and activation at a molybdenum–iron–sulfur cluster

• Published in: Nature chemistry Vol. 13; no. 7; pp. 666 - 670
• Main Authors: McSkimming, Alex, Suess, Daniel L. M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.07.2021; Nature Publishing Group
• Subjects: 631/45/49/1141; 639/638/263/49/1141; 639/638/263/910; Ammonia; Analytical Chemistry; Binding; Biochemistry; Biomimetics; Charge transfer; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Clusters; Cofactors; Coordination Complexes - chemical synthesis; Coordination Complexes - chemistry; Coordination compounds; Electropositivity; Embedding; Inorganic Chemistry; Iron; Iron - chemistry; Ligands; Molybdenum; Molybdenum - chemistry; Nitrogen - chemistry; Nitrogen compounds; Nitrogen fixation; Nitrogenase; Nitrogenase - chemistry; Nitrogenation; Organic Chemistry; Oxidation; Oxidation-Reduction; Physical Chemistry; Sulfur; Sulfur - chemistry; Titanium
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/s41557-021-00701-6

The Fe–S clusters of nitrogenases carry out the life-sustaining conversion of N 2 to NH 3 . Although progress continues to be made in modelling the structural features of nitrogenase cofactors, no synthetic Fe–S cluster has been shown to form a well-defined coordination complex with N 2 . Here we report that embedding an [MoFe 3 S 4 ] cluster in a protective ligand environment enables N 2 binding at Fe. The bridging [MoFe 3 S 4 ] 2 (μ-η 1 :η 1 -N 2 ) complex thus prepared features a substantially weakened N–N bond despite the relatively high formal oxidation states of the metal centres. Substitution of one of the [MoFe 3 S 4 ] cubanes with an electropositive Ti metalloradical induces additional charge transfer to the N 2 ligand with generation of Fe–N multiple-bond character. Structural and spectroscopic analyses demonstrate that N 2 activation is accompanied by shortened Fe–S distances and charge transfer from each Fe site, including those not directly bound to N 2 . These findings indicate that covalent interactions within the cluster play a critical role in N 2 binding and activation. Although iron–sulfur cofactors are known to carry out biological nitrogen fixation, how these clusters bind dinitrogen remains poorly understood. Now, a dinitrogen complex of a synthetic iron–sulfur cluster has been characterized, and electronic cooperation in the cluster has been shown to result in strong N–N bond activation.