Iron Hydride Detection and Intramolecular Hydride Transfer in a Synthetic Model of Mono-Iron Hydrogenase with a CNS Chelate

We report the identification and reactivity of an iron hydride species in a synthetic model complex of monoiron hydrogenase. The hydride complex is derived from a phosphine-free CNS chelate that includes a Fe–CNH(O) bond (carbamoyl) as a mimic of the active site iron acyl. The reaction of [(OCHNNpySMe)­Fe­(CO)2(Br)] (1) with NaHBEt3 generates the iron hydride intermediate [(OCHNNpySMe)­Fe­(H)­(CO)2] (2; δFe–H = −5.08 ppm). Above −40 °C, the hydride species extrudes CH3S– via intramolecular hydride transfer, which is stoichiometrically trapped in the structurally characterized dimer μ2-(CH3S)2-[(OCHNNPh)­Fe­(CO)2]2 (3). Alternately, when activated by base (tBuOK), 1 undergoes desulfurization to form a cyclometalated species, [(OCNHNCPh)­Fe­(CO)2] (5); derivatization of 5 with PPh3 affords the structurally characterized species [(OCNHNC)­Fe­(CO)­(PPh3)2] (6), indicating complex 6 as the common intermediate along each pathway of desulfurization.