In order to establish a quantitative relationship between the different heavier carbenes, we examined whether the energy profile for the H2 activation with germylenes can be predicted based on the silylene energies. Regression of the silylene and germylene activation energies indeed yielded a linear relationship expressed by equation 1 (Figure ), which allows the prediction of the H2 activation barrier for germylenes with an accuracy higher than 6 kJ/mol. The relationship demonstrates that H2 activation with germylenes requires more energy than the activation with silylenes as expected due to the increasing stability of the +2 oxidation state of germanium. This stabilization can now be quantified. For a process which requires 100 kJ/mol with a silylene -i.e. which is just possible at room temperature -the predicted energy for the corresponding germylene is approx. 150 kJ/mol and thus requires elevated temperature. The reverse trend is seen in the reaction energies. Here, hydrogen activation with a germylene is at least 100 kJ/mol less exergonic (eq. 2).