RESONANCE RAMAN STUDIES OF [CPFE(CO)(2)](2) AND [CP-ASTERISK-FE(CO)(2)](2) - A PROBE OF PHOTOREACTIVE STATES AND INTERMEDIATES

[CpFe(CO)(2)](2) (1: Cp = eta(5)-C5H5) and its permethylated analog [C p()Fe(CO)(2)](2) (1(*): Cp(*) = eta(5)-C(5)Me(5)) were examined using Raman and resonance Raman spectroscopy. Raman bands associated with h igh-energy C-O stretches and low-energy Fe-Fe and Fe-(mu-CO) are detec ted at a variety of excitation wavelengths. The assignments of the C-O stretches and the calculation of carbonyl force constants are present ed. The resonance behavior of the C-O stretching modes in 1 and 1() i s correlated to their lower energy electronic absorption bands, and th ese results provide an indication of the molecular orbitals involved i n the electronic transitions. The spectra show evidence for the format ion of the CO-loss photoproducts Cp(2)Fe(2)(mu-CO)(3) (2) and Cp(2)() Fe(2)(mu-CO)(3) (2()) 2 and 2(*) exhibit rich resonance Raman spectra , including a number of overtones and combination bands of the low-ene rgy vibrational modes. Such spectra suggest a strong coupling between the Fe-Fe stretching and Fe-(mu-CO) breathing modes.