Infrared Spectrum of Methyl Lithium Monomer in Solid Argon

Continued matrix reaction of methyl radical and lithium atoms produces methyl lithium, CH3Li. Isotopic substitutions at all atomic positions verify the molecular identity and indicate that the monomeric species is isolated. The fundamental frequencies, which are slightly lower than those for methyl halides and reasonably near those for solid methyl lithium in mulls, lead to the potential constants kH–C=4.32 mdyn/Å, kH–C–H=0.50 mdyn·Å/rad2, kH–C–Li=0.12 mdyn·Å/rad,2 and kC–Li=0.78 mdyn/Å. The low H–C–Li bending force constant suggests a significant amount of ionic character in the C–Li bond.