VOLUME 5 NUMBER 2 (July to December 2012)

by Jean Sanabria-Chinchilla, Tianbiao Liu, Christine M. Thomas,Brett Savoie, Marcetta Y. Darensbourg and Manuel P. Soriaga*

Department of Chemistry, Texas A&M University, College Station, TX 77843

We have a long-standing interest in theelectrochemical characterization of syntheticanalogues of hydrogenase biocatalysts, withthe ultimate goal of parlaying the informationtowards the modification of the surfaces ofinexpensive electrodes by the immobilization of homogeneouscatalysts for H₂ production and/or uptake. The initial stage of thestudy is focused on the synthesis of suitably ligated base metalsor metal complexes with hydrogenase-like functional activityfollowed by the assessment of their electrochemical activities. Inthis regard, N-heterocyclic carbene (NHC) ligands have taken onremarkable roles, because of their unique steric and electronicproperties, in organometallic chemistry and homogeneouscatalysis. They are now also exploited as candidates in syntheticanalogues of bioorganometallic enzymes as in the [FeFe]-hydrogenase active site. In the present paper, we contrast theelectrochemical behaviors of the complex (μ-pdt)[Fe(CO)₃][Fe(CO)₂IMes] with the saturated analogue, SIMes (SIMes =1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidine) in the (μ-pdt)[Fe(CO)₃][Fe(CO)₂(SIMes)] complex, and with the protonatedimidazolium salts that are precursors of the NHC ligands, HNHC⁺Cl^-. Our goal was to further confirm and gain insight intothe nature of the 2-electron process of (μ-pdt)[Fe(CO)₃][Fe(CO)₂IMes] as well as to establish the extent to which theNHC ligands are involved with respect to the overall electronuptake by the complexes.