Inorganic Chemistry, Vol.49, No.13, 5853-5858, 2010
A Five-Coordinate [2Fe-2S] Cluster
A unique [2Fe-2S] cluster (1) with genuinely five-coordinate ferric ions has been synthesized and investigated both structurally and spectroscopically. The crystal structure of 1 as well as H-1 NMR data reveal that 2,6-bis(imidazol-2-yl)pyridine binds to the [2Fe-2S] core as a tridentate capping ligand. DFT calculations showing spin density on all coordinating atoms support this finding. Cluster 1 has also been characterized by Mossbauer and UV/vis spectroscopy, mass spectrometry, cyclic voltammetry, and magnetic susceptibility measurements. Significant spectroscopic properties that make 1 distinct from conventional [2Fe-2S] clusters include a rather small quadrupole splitting of 0.43 mm/s.