Dipole moments of halogenogermanes from non-resonant absorption of vapours

Abstract

The electric dipole moments of gaseous GeH₃Cl, GeH₃Br, GeH₃I, and CH₃GeCl₃ have been determined at 25°C by the microwave non-resonant absorption of vapours and/or by dielectric constant measurements. The loss tangent dependence on the pressure and transmitted power changes were measured in a resonant cavity at a fixed frequency 1216 MHz. The dielectric constant dependence on frequency and pressure changes has been measured in a similar cavity at a fixed frequency of 9547 MHz. The agreement between the loss measurement and the dielectric constant dipole moments are reasonable, despite the assumption that the molar polarization equals the atomic polarization and the lack of precise molecular parameters in halogenogermanes. Comparison of GeH₃X dipole moments with SiH₃X dipole moments suggests that either the (p→d)π bonding in GeH₃X gas phase molecules is not as important as in the analogous SiH₃X gas phase molecules or that the lowering and relative constancy of the SiH₃X moments is caused by factors other than (p→d)π interaction.