ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
O23. Iron Complexes Mimicking the Active Site of the Iron-Sulfur Cluster-
Free Hydrogenase
X. Hu and B. Obrist
Laboratory of Inorganic Synthesis and Catalysis, Institute of Chemical Science and Engineering, Ecole
Polytechnique Fédérale de Lausanne, EPFL-ISIC-LSCI, BCH 3305, Lausanne, CH 1015, Switzerland.
e-mail: xile.hu@epfl.ch
Three types of phylogenetically unrelated hydrogenases are known, including the [NiFe]- and [FeFe]hydrogenases
and the iron-sulfur cluster-free hydrogenase (Hmd). Hmd is a unique hydrogenase in that it
requires one single iron for function and it contains an interesting pyridone cofactor. Our lab is developing the
coordination chemistry of iron and pyridones to probe their roles in the enzymatic H2 activation by Hmd.
Current data (Shima and Thauer et al.) suggest that in the active form of Hmd, the iron center is coordinated by
two cis-CO ligands, one cysteine S atom, one nitrogen/oxygen atom from the pyridone portion of the cofactor,
and one unknown fifth ligand (Figure inset, top). We choose to use simple pyridone ligands to mimic the
pyridone cofactor and thiolate ligands to mimic the cysteine S ligand (Figure inset, bottom). Starting from
Fe(CO)5, we were able to synthesize iron complexes containing a pyridone ligand together with two ciscarbonyls.
These complexes were characterized by a variety of spectroscopic methods and provided important
reference data points for the geometric and electronic structure of Fe in Hmd itself. Furthermore, the solid-state
structure of some of these model complexes was determined and the binding of pyridone to iron was revealed.
We will present our synthetic, spectroscopic, structural, and reactivity studies on these iron model complexes
together with the implications for Hmd.
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