Isolated MH stretching frequencies, anharmonicities, and dissociation energies in silanes, germanes, phosphines, and arsines

The fundamental and first overtone MH stretching bands have been recorded on a Nicolet 7199 FT IR spectrometer from the following species: MHD/sub 3/, MeMHD/sub 2/, Me/sub 2/MHD, Me/sub 3/MH (M = Si, Ge); MHD/sub 2/, MeMHD, Me/sub 2/MH (M = P, As); SiHF/sub 3/, SiHCl/sub 3/, SiHCL/sub 3/, Si/sub 2/HD/sub 5/; GeHD/sub 2/X (X = F, Cl, Br, I). The fundamental ..nu../sub SiH/ band of PhSiHD/sub 2/ was also observed. Treating the MH bond as a diatomic molecule, values of ..omega../sub e/, chi/sub e/, D/sub lin/, and D/sup 0//sub 0/ are deduced. The spectroscopic data clearly indicate that methyl substitution weakens the MH bond, in conflict with evidence from recent iodination kinetics studies. Trends in MH bond anharmonicity are observed and discussed.