Infrared Spectrum of Dichlorocarbene in Solid Argon

Abstract

The matrix reaction of lithium atoms and carbon tetrachloride produces the CCl3 radical followed by secondary reaction of Li with CCl3 to yield a sufficient concentration of dichlorocarbene for infrared spectral study. Natural chlorine isotopes, carbon‐13 and bromine substitution, and loss of CCl2 absorptions accompanied by growth of C2Cl4 absorptions on sample warming furnish convincing evidence that dichorocarbene is isolated in the argon matrix. Assignments of the C‐Cl stretching vibrations for the 12C35Cl2, 12C35Cl37Cl, 13C35Cl2, and 12C35Cl37Cl species are supported by normal coordinate calculations. For the most abundant isotopic species, ν 1 = 719.5 and ν 3 = 745.7 cm −1 , and ν 2 , the weak bending mode, was not detected. The stretching force constants F τ = 2.86 mdyn / Å and F ττ = 0.27 mdyn / Å indicate that C‐Cl single bonds are present in dichlorocarbene, making it unlikely that the electron deficiency of the carbon atom is relieved by pi bonding with chlorine.