| In this dissertation, we describe the design and synthesis of some novel model complexes for the diiron subsite of [FeFe]-hydrogenase. These complexes were investigated spectroscopically and electrochemically, which may shed light on one's further understanding of the catalytic mechanism of the [FeFe]-hydrogenase.This dissertation is mainly concerned with following two aspects:Two hexa-iron clusters {[Fe2(CO)5L][Fe2(CO)6][LFe2(CO)6]} (1) and {[Fe2(CO)6L]2[Fe2(CO)6]} (2) were synthesised from the reaction of the tripodal ligand (H3L = CH3C(CH2SH)3) with Fe3(CO)12. The inter-conversion between the two clusters was probed by using infrared and UV-visible spectroscopic techniques as well as electrochemistry. DFT calculations indicate that the inter-conversion process between the two clusters involve two transition states (TS1 and TS2) and one intermediate species with bridging CO, [2-1].Three precursor of model complexes functionalised with hydroxyl or phenoxyl groups, [(SCH2)2C(CH3)(CH2OH)] Fe2(CO)6 (3), o-(C6H4OH)2(SCH2)2Fe2(CO)6 (7) and [o-HOC6H4CH2C(CH3)(SCH2)2] Fe2(CO)6 (10), were synthesised. These complexes were fully characterised by using infrared, UV/Vis, nuclear magnetic resonance spectroscopic techniques as well as Micro-analysis. Deprotonation of these complexes using NaH led to formation of model complexes which possess Fe(I)-OR (R = organic moiety) bond, [Fe2(CO)5(SCH2)2C(CH3)(CH2O)]- (4), [o-(C6H)4O)2(SCH2)2Fe2(CO)4]2- (8) and {[o-OC6H4CH2C(CH3)(SCH2)2]Fe2(CO)5}-(11), as suggested by their infrared spectra. And we also investigated into their stability initially. To our best knowledge, this is the first examples of model complexes possessing Fe(I)-OR, which ressemble the similar bond found in the diiron subunit of the H-cluster of the [FeFe]-hydrogenase at its rest state.
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