Modeling [FeFe] hydrogenase: Synthesis and protonation of a diiron dithiolate complex containing a phosphine-N-heterocyclic-carbene ligand

The ligand exchange reaction of IMe-(CH2)2-PPh2 (IMe = 1-methyimidazol-2-ylidene) and the hexacarbonyl complex [{Fe2{μ-S(CH2)3S}(CO)6] (1) resulted in the formation of the chelated complex [{Fe2{μ-S(CH2)3S}(CO)4(IMe-(CH2)2-PPh2)] (2). The molecular structure of 2 was confirmed by spectroscopic and X-ray analyses. This complex catalyzes proton reduction. Low temperature NMR studies on the protonation of 2 revealed the formation of a terminal hydride intermediate.