Biomimetic Study Of Mono Iron Hydrogenase Active Site And Catalytic Hydrogenation Reactivity

Biomimetic chemistry of hydrogenase is the frontier of the current organometallic chemistry research. This field focused on structure and function simulation of hydrogenase active center. Hydrogenase is a class of microorganisms metalloenzymes molecule capable of catalyzing the use of hydrogen or reducing protons to hydrogen. The biomimetic studies on structures and functions of hydrogenase is significant and valuable for the development of non-noble metal catalysts.This study conducted the synthesis and characterization of model compound of mono iron hydrogenase Fe(CO)2PR3(NN)(R = Cy, Ph, NN = o-phenylendiamine dianion ligand), explored the protionation/deprotonation process and catalytic hydrogenation reactivity.By conducting synthesis experiment under the conditions of different solvents, stirring speed and adding orders of reactants, an optimal synthetic process was summaried. In that way, the target complex was synthesised and separated successfully.The center Fe(II) ion of complex was ligated by phosphine ligand, two cis-CO ligands, one bidentate donor atom of o-phenylenediamine, through the nitrogen atom.The complexes were characterized by 1H NMR, 13 C NMR, IR and EA. Both of them has been determined by the single crystal X-ray diffraction measurement for the structural characterization. With the analysis of infrared spectroscopy, the similar properties of mono iron hydrogenase and the model compouds were discussed.In the further catalytic reactivity mimic study, reverible protonation of the ophenylenediamine(N2H2Ph) ligand was identified by the IR spectroscopy and DFT calculations, which was considered to function as an internal base. It is indicated that N2H2 Ph ligand is a proton acceptor, somewhat analogous to the cysteine thiolate ligand in the [Fe]-hydrogenase. In the acetone, Fe(CO)2PR3(NN) binded a H+ to form Fe(CO)2PR3(NN)·H+ with the addition of HBF4. Moreover, Fe(CO)2PPh3(NN)·H+ was found active in the CV process, and FeI/Fe0 was inferred to be the active center of hydrogenation in that condition.Complex Fe(CO)2PCy3(NN) can catalyze the reduction of benzoquinone to hydroquinone in ethanol solution in mild conditions with the conversion 89% and yield of 40%. It is the first time to implement the catalytic hydrongenation effectively in the effort of function simulation.