Vapour phase far-infrared studies of η-bonded metal carbonyls, (1,3-butadieneiron tricarbonyl, cyclopentadienylmanganese tricarbonyl and methylcyclopentadienylmanganese tricarbonyl)

Abstract

Far-infrared spectra of 1,3-butadieneiron tricarbonyl, C 4H 6Fe(CO) 3, cyclopentadienyl-manganese tricarbonyl, C 5HMn(CO) 3 and methylcyclopentadienylmanganese tricarbonyl, CH 3C 5H 4Mn(CO) 3 in the vapour phase have been reported first time in the region 500-10 cm −1. An assignment of the frequencies on the basis of local symmetry of Fe(CO) 3 fragment explain most of the observations, but the FeCO stretching modes of E symmetry are split. The C 4H 6 vibrations are assigned on the basis of C S symmetry. For CpMn(CO) 3 and MeCpMn(CO) 3 particular reference is made to the assignment of the metal-ring modes. This assignment has been discussed in term of previous assignment given for (in liquid phase and Nujoll mull) other ν-cyclopentadienyl and related compounds, including ferrocene, dimethylferrocene, benzenechromium tricarbonyl and toluenechromium tricarbonyl.