A new iron-based hydrogenase mimic, [Fe(C-5(p-C6H4Br)(5))(CO)(2)Br], was synthesised and characterised using X-ray crystallography. Two analogous catalytic precursors, [Fe(C5Ar5)(CO)(2)Br] (Ar = C6H5; p-C6H4Br), were also analysed electrochemically in order to investigate how bulkier and more electron withdrawing C5Ar5 ligands affect the catalytic generation of hydrogen from trichloroacetic acid. Compared to previously reported iron-based cyclopentadienyl analogues, these complexes were found to have smaller overpotentials and larger turnover numbers. The [Fe(C-5(p-C6H4Br)(5))(CO)(2)Br] complex was found to be the most efficient of the two catalytic precursors with a turnover number of 25, an overpotential of around 310 mV and a faster rate of reaction compared to [Fe(C5Ph5)(CO)(2)Br]. (C) 2017 Elsevier B.V. All rights reserved.