Abstract Infrared spectra of M(CC-CH 3) 4 ( M = Si, Ge, Pb) and M(CC-CH 3) 3 ( M = P, As, Sb) have been measured from 33 to 4000 cm −1 as solids dispersed in KBr and Nujol and as solutions in CCl 4 and CS 2 (and as a vapor for As(CC-CH 3) 3 only). Raman spectra were measured in the solid state and for solutions in several solvents. Polarizations were obtained in solution. T d symmetry was assumed for M(CC-CH 3) 4 and C 3 v for M(CC-CH 3) 3 and was completely satisfactory. Most of the spectroscopically active fundamentals could be assigned with little difficulty.