The vibrational spectrum of (butadiene) iron tricarbonyl

The vibrational spectrum of C 4 H 6 Fe(CO) 3 has been studied. An assignment of the frequencies on the basis of the local symmetry of the Fe(CO) 3 fragment (C 3v ) explains most of the observations, but the FeC and CO stretching modes of E symmetry are both split. Therefore the effective symmetry must be C s The C 4 H 6 vibrations are assigned on the basis of C s symmetry throughout.