Vibrational spectra of tricarbonyl(π-cyclopentadienyl)manganese, bis-[tricarbonyl(π-cyclopentadienyl)molybdenum], and their deuteriated derivatives

Abstract

The i.r. and laser Raman spectra of (π-C₅H₅)Mn(CO)₃, [(π-C₅H₅)Mo(CO)₃]₂, and their deuteriated derivatives have been measured and assignments made. The data on the manganese complex reveal that interpretation of the solution spectrum of the C₅H₅-Mn moiety on the basis of C_5v‘local’ symmetry may only be regarded as an approximation. Product rule calculations have been carried out for the a₁ ring modes of both complexes. For the manganese complex only calculations have also been done for e₂ modes and have been used as an aid to assignment of the spectrum of the deuteriated derivative. The spectrum of (π-C₅H₅)Mn(CO)₃ has been studied as a gas (i.r. only), liquid, and solid (at room temperature and 77 K) and spectral differences arising from change of state and temperature discussed. The ‘local’ symmetry approach has been shown to be no longer applicable for assignment of the spectrum of both complexes in the solid state. Methods used for obtaining the spectra are described.