The third hydrogenase: A ferracyclic carbamoyl with close structural analogy to the active site of Hmd

The synthesis of a close structural analogue of the active site of [Fe]-hydrogenase is described (see structure; C gray, H dark blue, Fe green, N light blue, O red, S yellow). Nature most probably constructs the five membered ferracyclic ring to poise the 2-hydroxy pyridine substituent in a position to assist the heterolytic cleavage of dihydrogen, and the accessibility of the analogue should now provide opportunities for probing this.