New light on the stretching vibrations,lengths and strengths of CH,SiH and GeH bonds

Recent developments in the field of ‘isolated’ MH stretching frequencies are reviewed. A new r_O versus ν^is_CH correlation plot is described. The ‘local mode’, high overtone, approach to CH bond strengths is compared with the ν^is_CH one. 2ν^is_CH studies are described which also lead to anharmonicities of individual bonds. In current work on ν^is_SiH and ν^is_GeH, conformational effects of halogens, lone pairs and methyl groups are found similar to those in the carbon analogues. These create problems in assessing substituent effects. New correlations with Σσ^* for alkyl groups are very different from previous ones.