Fourier transform infrared-matrix isolation study of gaseous cerium dicarbide species

Abstract

For the first time, experimental evidence was obtained for the presence of a C=C bond in the structure of a gaseous rare-earth dicarbide species. A value of 1754.5 cm−1 could be unambiguously determined for the corresponding stretching frequency in the Ce12C2 molecule. Strong support was also obtained for the assignment of a weak broadband centered at 1720.5 cm−1 to analogous modes in 13C monosubstituted cerium dicarbide molecules. The possible assignment of a weak band at 789.1 cm−1 to stretching modes of Ce–C bonds in Ce12C2 molecules remains tentative. In order to fit the above assignments, the normal coordinate analysis was performed for each of the structures which preserve the C=C bond and the results were compared.