[NiFeSe] hydrogenase enzymes are particularly suitable catalysts for H₂ evolution, because they exhibit high catalytic activities and fast reactivation from O₂ inactivation compared with their thiolate analogues and other hydrogenases. This is thought to be caused by the selenium residue.

To investigate the reactivity of [NiFeSe] hydrogenases, Claire Wombwell and Erwin Reisner, University of Cambridge, UK, synthesized a dinuclear model of the [NiFeSe] hydrogenase active site, namely [NiFe(‘S₂Se₂‘)(CO)₃] (H₂‘S₂Se₂‘=1,2-bis(2-thiabutyl-3,3-dimethyl-4-selenol)benzene). The model compound (pictured) was generated by the reaction of a nickel selenolate complex with [Fe(CO)₃bda] (bda = benzylideneacetone).

The team characterized the complex spectroscopically and electrochemically, and investigated its electrocatalytic activity for H₂ evolution. According to the researchers, the catalytic effect does not result from homogeneous catalysis, but from a solid deposit containing Ni, Fe, S, and Se formed from the complex on the electrode surface when a potential was applied. The model compound thus acts as a precursor for a heterogeneous catalyst.

• Synthetic Active Site Model of the [NiFeSe] Hydrogenase,
  Claire Wombwell, Erwin Reisner,
  Chem. Eur. J. 2015.
  DOI: 10.1002/chem.201500311