INFRARED SPECTRAL EVIDENCE FOR TRIHALOMETHYLLITHIUM AND -SODIUM COMPOUNDS IN SOLID ARGON

The matrix reaction of alkali metal atoms and perbromochloromethanes produces the trihalomethyl radical followed by a secondary reaction of metal atoms with CX3 to yield a sufficient concentration of the trihalomethyl alkali metal compounds for infrared spectral study. Use of the five perbromochloromethane precursors with lithium-6, lithium-7, and sodium verifies the molecular identity. Assignments to the antisymmetric carbon-halogen stretching frequencies are 521 and 462 cm-1 for the chlorine and bromine species, respectively, while the lithium-6 stretching frequencies are 437 and 391 cm-1, respectively, for the chlorine and bromine molecules. The carbon-halogen frequencies lead to markedly lower force constants than calculated for the carbon tetrahalides which suggests that the CX3 group has a significant amount of anionic character.