Vibrational Spectra and Structure of Organogermanes. IV. Normal Vibrations and Free Rotation in Phenylgermane

Abstract

The infrared spectra of liquid phenylgermane, phenylgermane-d3, phenylgermane-d5, and phenylgermane-d8 have been recorded from 4000–33 cm−1. The Raman spectra of the liquids have also been recorded and depolarization values have been measured. The vapor-phase spectra show that the germyl group is freely rotating for these molecules. Thus, the local symmetry of the phenyl ring is C2υ and the vibrations have been assigned according to this symmetry. The effective symmetry of the GeH3 and GeD3 groups is essentially C3υ. All spectra have been interpreted in detail, and the 39 fundamental vibrations have been assigned based on previous assignments of benzene and its isotopic derivatives, depolarization ratios, and vapor-phase infrared band contours. The assignments are shown to be consistent by means of the Teller–Redlich product rule and by application of the sum rule. The free rotation of the germyl group shows that the sixfold barrier to internal rotation around the C–Ge bond is negligibly small.