Computational definition of a mixed valent Fe(II)Fe(I) model of the [FeFe]hydrogenase active site resting state. Academic Article uri icon


  • Density-functional calculations have been used to examine the electronic structure and bonding in the recently reported complex [(PMe(3))(CO)(2)Fe(mu-pdt)(mu-CO)Fe(CO)(IMes)](+) (1(+), IMes=1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene). This mixed valent Fe(II)Fe(I) complex features a rotated geometry that places a carbonyl ligand in a semi-bridging position, which makes it an accurate model of the S =(1/2) resting state of the [FeFe]-hydrogenase active site. Calculations indicate that the unpaired electron in this complex lies almost entirely on the rotated iron center, implying that this iron remains in the Fe(I) oxidation state, while the unrotated iron has been oxidized to Fe(II). The frontier molecular orbitals in 1(+) are compared with those in the neutral Fe(I)Fe(I) precursor (PMe(3))(CO)(2)Fe(mu-pdt)(mu-CO)Fe(CO)(IMes) at both its optimized geometry (1) and constrained to a rotated geometry (1(rot)). These theoretical results are used to address the role of the bridging CO ligand in 1(+) and to predict reactivity patterns; they are related back to the intricate biological mechanism of [FeFe]-hydrogenase.

published proceedings

  • J Inorg Biochem

author list (cited authors)

  • Thomas, C. M., Darensbourg, M. Y., & Hall, M. B.

citation count

  • 47

complete list of authors

  • Thomas, Christine M||Darensbourg, Marcetta Y||Hall, Michael B

publication date

  • November 2007