| Summary: | A dithiolate diiron subsite is an essential component of the H-cluster of [FeFe]-hydrogenase, it provides the centre at which protons and electrons are reversibly combined to produce dihydrogen and is fed electrons from the other component, a 4Fe4S cluster to which it is attached by a cysteinyl bridge. Much research has focused on developing synthetic analogues of the subsite, both to inform an understanding of the chemistry and spectroscopy of the natural system and to explore their technological potential as electrocatalysts for fuel or producer cell applications. This thesis reports new approaches for building modifications into subsite analogues which have the potential to alter their structure and function. Synthetic methods are described for: (i) introducing Lewis base or Lewis acid groups into the second coordination sphere of a diiron unit (ii) exploiting the N-basicity of coordinated cyanide to build H-bonding or bridging cyanide systems (iii) incorporating carborane structural units as part of a dithiolate diphosphine framework. Key results include the X-ray crystallographic characterisation of a zwitterionic complex in which a Ru photosensitiser group is linked via bridging cyanide to a diiron hydrogenase subsite analogue, the characterisation of hydrogen bonding adducts of activated bis-ureas with dicyanide dithiolato diiron complexes by mass and FTIR spectroscopy, and the first example in which a borane Lewis acid is attached to a diiron unit, an approach which may presage cleavage of molecular hydrogen by a novel frustrated Lewis acid Lewis base system.
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