Fe-III-hydroperoxo and peroxo complexes with aminopyridyl ligands and the Resonance Raman spectroscopic identification of the Fe-O and O-O stretchingmodes

Nonheme Fe-III-hydroperoxo and Fe-III-peroxo complexes with aminopyridyl-ty pe ligands have been prepared and characterized by UV/Vis, EPR, mass and Re sonance Raman (RR) spectroscopy. The Fe-III(OOH) species are low-spin and e xhibit a deep purple color due to the ligand-to-metal charge transfer (LMCT ) band centered at ca. 550 nm. The RR spectra of the Fe-III(OOH) complexes display two bands at ca. 620 and 800 cm(-1) that are assigned to the respec tive Fe-O and O-O stretching modes on the basis of the characteristic H/D a nd O-16/O-18 frequency shifts. Upon deprotonation, Fe-III(O-2) species are obtained which possess a high-spin configuration of nearly axial symmetry a nd a LMCT transition in the near infrared (ca. 750 nm). The frequencies of the Fe-O and O-O stretching modes at ca. 465 and 820 cm(-1), as well as the ir respective O-16/O-18 shifts of -16 and -45 cm(-1), indicate an eta(2) co ordination geometry for the Fe-III(O-2) complex.