Relative rates of germylene and silylene insertions into alkylgermanes in competition with digermane and disilane

The relative rates of GeH2 insertions into the GeH bonds on a per bond basis were found to be in the order: (CH3)3GeH > (CH3)2GeH2 > Ge2H6 > CH3GeH3. These results were determined from competitive reactions of GeH2 with Ge2H6 and alkylgermanes. The relative rates of SiH2 insertions into Si2H6 versus (CH3)2 GeH2 and (CH3)3GeH were also obtained. These relative rates and those previously reported were examined for a correlation with the bond energy of the bond undergoing insertion and with the negative charge of the hydrogen in the bond undergoing insertion. The correlation with bond energies was successful for germanes or silanes considered separatively but not for SiH2 insertions into CH3SiH3, CH3GeH3 and CH3PH2. The correlation with the negative charge on the hydrogen was unsuccessful only where steric factors could be important.