Multimetallic nitride species, especially those containing biologically related iron or molybdenum, are fundamentally important to understand the nitrogen reduction process catalysed by FeMo‐nitrogenase. However, until now, there remains no report about the construction of structurally well‐defined FeMo heteronuclear nitrido complex and its reactivity toward ammonia formation. Herein, a novel thiolate‐bridged FeIIMoVI complex featuring a bent Fe−N≡Mo fragment is synthesized and structurally characterized, which can be easily protonated to form a μ‐imido complex. Subsequently, through the proton‐coupled electron transfer (PCET) process, this imido species can smoothly convert into the μ‐amido complex, which can further undergo reductive protonation to afford the FeMo complex containing an ammine ligand. Overall, we present the first well‐defined {Fe(μ‐S)2Mo} platform that can give a panoramic picture for the late stage (N3−→NH2−→NH2−→NH3) of biological nitrogen reduction by the heterometallic cooperativity.
Coordinatively unsaturated sulfur-supported iron complexes are conceived as suitable functional models for probing the potential biomimetic reactivity. In this regard, it is of continuous interest to construct this class of metallic complexes and investigate their unique properties for prospective applications. Here, we describe synthesis, characterization, and reactivity of a series of thiolate-bridged di-or multinuclear iron complexes supported by bulky 1,2,4-tri(tert-butyl)cyclopentadienyl (Cp′) ligands. Especially, detailed studies on variable-temperature solidstate magnetic susceptibility measurement and zero-field 57 Fe Mossbauer spectroscopy at different temperatures reveal that the two iron centers in desirable [Fe II (μ-SR) 2 Fe II ]-type complexes are all in intermediate-or high-spin configurations. Notably, when the substituent in the bridging thiolate ligand is the isopropyl group, the corresponding diiron complex exhibits temperature-induced reversible phase transition phenomenon. Its temperature-dependent magnetic susceptibility under successive cycles exhibits an 8 K wide hysteresis of magnetization caused by the reversible phase transition. Moreover, its single-crystal X-ray diffraction analyses at different temperatures clearly demonstrate the existence of phase transition accompanied by obvious thermal expansion upon heating, during which the corresponding space group varied from non-central tetragonal P4̅ 2(1)c below the inflection point temperature to central tetragonal P4(2)/mbc above the inflection point temperature. In addition, these new iron complexes bearing sulfur donors are all proved to be good catalysts for the reductive silylation of N 2 .
Biomimetic di- or multimetallic complexes featuring NxHy species in a sulfur-rich coordination sphere have attracted considerable attention in modelling the possible scenarios of biological nitrogen fixation by nitrogenases. Although the...
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