New Raman data for solutions, powders, and oriented single crystals are reported which allow a consistent assignment of the vibrational spectra of the title compounds. The four Raman-active v(C0) modes for Mn2(CO)lo are at 21 16(al), 2024(e,), 1 997(a,), and 1981 (e3) cm-l. Low-frequency spectra of considerably improved quality are also presented. All of the a, bands have been located for Re,(CO),,and all but one for Mn,(CO),,for solutions. LE1 7RHDESPITE the considerable effort expended upon the spectra of Mn2(CO)lo1-14 and, to a lesser extent, Re,-(CO)10,1-3,7J1-16 anomalies remain both in the data and the assignments for these molecules, even in the carbonyl stretching region. We report new experimental evidence which leads to a reassignment for both molecules.

Raman and far-i.r. spectra are reported and assigned for the solid complexes Cr(CO),(n-arene) (arene = benzene, aniline, toluene, methyl benzoate, anisole, and hexamethylbenzene) and M (CO),(n-mesitylene) (M = Cr, Mo, or W). For the benzene complex, discussion is based upon the factor group, but in the other cases the molecular point-symmetry proves to be an adequate approximation. C,, local symmetry is an inadequate approximation when discussing the skeletal modes of complexes of monsubstituted arenes.

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Raman and i.r. spectra are reported and assigned for the compounds Mn2(CO)lo. Mn(CO),X (X = CI or Br), and Hg [M n ( C O ) 51 2.