Vibrational Overtone Spectroscopy and Overtone Intensities of Cyclohexadiene Iron Tricarbonyl and 1,3-Cyclohexadiene

摘要

The CH stretching overtone spectra ofliquid cyclohexadiene iron tricarbonyl (CHDIT) have been reconJ for the fIrst, second, andthird,overtone regions (#DELTA#v = 2-4). The gaseous spectrum of CHDIT has also be obtained for the first overtone region (#DELTA#v = 2). Observed transitions are assigned to the overtones of diffen nonequivalent CH bonds and to the local mode-normal mode combination bands. Oscillator strengths ha been calculated with the harmonically coupledanharmonic oscillator (HCAO) local mode model and ab inil dipole moment functions. The theoretical values have been compared to the experimental oscillator strengt and agree well with experiment. The comparison of the overtone spectrum of CHDIT to the correspondil spectrum of uncomplexed 1,3-cyclohexadiene reveal changes that occur in the ligand upon complexati< with iron tricarbonyl. The presence of the metal lengthens the terminal olefinic CH bond by 0.002 A ar shortens the non terminal olefinic CH by 0.001 A. The axial and equatorial CH bonds of the free ligal1 become similar in length in the complex. The implications of the observed spectral features to the structw and bonding in the complex are discussed.