The biological reduction of N2 is known to occur at the nitrogenase FeMo-cofactor, which is a complex metal-sulfur cluster. Although various metal-sulfur clusters have been synthesized as structural analogues over decades, their use in the activation of N2 has proven challenging to realize, and even the FeMo-cofactor extracted from the protein has not been found to reduce N2. In this study, we made an initial step toward modeling the N2-reducing function of the FeMo-cofactor, and found that cubic [Mo3S4M] clusters with an appropriate reaction sites M are able to activate N2. Cubic [Mo3S4M] clusters with groups 4-10 first-row transition metal halides were synthesized by accommodating M to organometallic [Mo3S4] platforms.1,2,3 One of these cubic clusters, the [Mo3S4Ti] cluster (1), was reduced by KC8 to selectively generate a Ti-based reaction site for the activation of N2.1 The resulting cluster 2 possesses an N2 moiety bridging two [Mo3S4Ti] cubes. The bridging N2 moiety in 2 was converted into sub-stoichiometric amounts of NH3 (and N2H4) upon treatment with Brønsted acids in the presence of KC8.1 Some other reactions employing different cubic clusters4 will also be discussed.

Bio-inspired cubic metal-sulfur clusters for N2 activation

ACS Spring 2022

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