Infrared multiphoton dissociation spectrum of CF_3Mn(CO)_4I^-

An IR multiphoton dissociation spectrum of CF_3Mn(CO)_3I^− has been obtained using Fourier transform ion cyclotron resonance spectroscopy combined with a line-tunable CW CO_2 laser in the 925–1085 cm^(−1) wavelength range. The trifluoromethyl group in the anion shows two absorption maxima at 1055 and 975 cm^(−1), which correspond to a CF stretch of A_1- and E-type symmetry respectively. From comparisons of the ligand effect on the stretching force constant of CO in place of CF_3 in cis and trans isomeric CF_3Mn(CO)_4I^− ions, it is suggested that a cis isomer is responsible for the observed C-F stretching frequencies.