The Infra-Red and Raman Spectra of Dimethyl Mercury and Dimethyl Zinc

Abstract

The infra‐red spectra of dimethyl mercury and dimethyl zinc and the Raman spectrum of dimethyl mercury have been observed. A frequency assignment has been proposed for dimethyl mercury, and that of dimethyl zinc has been modified. The results support a linear C—M—C structure, in agreement with quantum‐mechanical predictions, and also D_3h′ symmetry with essentially free rotation of the methyl groups. A normal coordinate analysis has been made of the fundamental frequencies and valence‐type force constants deduced therefrom. The values of the force constants pertaining only to the methyl groups agree very well with values obtained in other molecules; others indicate the relatively easy deformability of the C—M—C figure axis. Differences between the dimethyl mercury and dimethyl zinc force constants indicate greater ionic character in the C–Zn bond. Values of 2.45 and 2.39×10⁵ dynes/cm are obtained for the C–Hg and C–Zn stretching force constants. The relation of these values to current suggestions concerning the dependence of bond strengths on atomic parameters is briefly discussed.