INFRARED SPECTRUM AND VIBRATIONAL ASSIGNMENTS FOR PENTACARBONYLMANGANESE HYDRIDE

The infrared spectrum of pure HMn(CO)5 in the region 4000-300 cm-1 has been obtained in the vapor phase. The observed spectrum has been analyzed to distinguish the fundamental frequencies, the rotational-vibrational band structure, and overtone and combination frequencies. An assignment of the observed vapor-phase frequencies to the fundamental modes of vibration has been made based on C4v symmetry, which the -Mn(CO)5 moiety is known to possess in the solid state. The positions of middle-frequency bands of DMn(CO)5 are reported and used to test the C4v assignment with the Teller-Redlich isotope product rule. It is shown that it is not necessary to assume lower than C4v symmetry for HMn(CO)5, as has been done in all previous considerations of the entire infrared spectrum of HMn(CO)5. © 1969, American Chemical Society. All rights reserved.