Synthesis of the P-Cluster Inorganic Core of Nitrogenases

The [8Fe−7S] core of the P-clusters in nitrogenases is unique among the known [Fe−S] clusters which are essential to electron-transfer processes in nature. The [8Fe−7S] cluster has been thought unstable and to exist only in protein environments. We found that this unusual [8Fe−7S] structure can be self-assembled from the reaction of Fe(II) bis-amide, tetramethylthiourea, 2,4,6-triisopropylbenzenethiol, and elemental sulfur in a specific mole ratio. The structure of the complex isolated therefrom closely resembles that of the reduced form (PN) of the P-clusters, while the 6Fe(II)2Fe(III) oxidation state was manifested by the Mössbauer study.