Synthetic Active Site Model of the [NiFeSe] Hydrogenase.

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Wombwell, Claire 

A dinuclear synthetic model of the [NiFeSe] hydrogenase active site and a structural, spectroscopic and electrochemical analysis of this complex is reported. [NiFe('S2Se2')(CO)3] (H2'S2Se2' = 1,2-bis(2-thiabutyl-3,3-dimethyl-4-selenol)benzene) has been synthesized by reacting the nickel selenolate complex [Ni('S2Se2')] with [Fe(CO)3bda] (bda = benzylideneacetone). X-ray crystal structure analysis confirms that [NiFe('S2Se2')(CO)3] mimics the key structural features of the enzyme active site, including a doubly bridged heterobimetallic nickel and iron center with a selenolate terminally coordinated to the nickel center. Comparison of [NiFe('S2Se2')(CO)3] with the previously reported thiolate analogue [NiFe('S4')(CO)3] (H2'S4' = H2xbsms = 1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene) showed that the selenolate groups in [NiFe('S2Se2')(CO)3] give lower carbonyl stretching frequencies in the IR spectrum. Electrochemical studies of [NiFe('S2Se2')(CO)3] and [NiFe('S4')(CO)3] demonstrated that both complexes do not operate as homogenous H2 evolution catalysts, but are precursors to a solid deposit on an electrode surface for H2 evolution catalysis in organic and aqueous solution.

active sites, enzyme models, hydrogenase, selenium, structural models, Biomimetic Materials, Catalysis, Catalytic Domain, Crystallography, X-Ray, Hydrogenase, Models, Molecular
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Engineering and Physical Sciences Research Council (EP/H00338X/2)
This work was supported by the Engineering and Physical Sciences Research Council (EP/H00338X/2), the Christian Doppler Research Association, and the OMV group. We thank Mr Dirk Mersch for recording SEM and EDX, Dr John Davies for collecting and refining the crystallographic data, and the National EPSRC XPS User’s Service (NEXUS) at Newcastle University for recording XPS data. Benjamin C. M. Martindale is acknowledged for his help with XPS analysis. Dr Christine Caputo and Janina Willkomm are acknowledged for helpful comments.