Thus far, we have focused on enhancing the reactivity of metallylenes for small molecule activation. The activation of small molecules is an essential step toward their valorization, but it must be rather thermally neutral to ensure that the activated metallylene does not fall into a thermodynamic well, which would raise the reaction barrier for subsequent steps. The redox-based catalytic cycle of metallylenes consists of the oxidative addition of small molecules, forming a tetrel(IV) intermediate, followed by reductive elimination that regenerates the tetrel(II) metallylene, Scheme 4. For instance, first, a metallylene activates H₂, enabling hydrogenation reactions, such as the conversion of formaldehyde to methanol, thereby reducing the tetrel(IV) intermediate. However, if the H₂-activated metallylene intermediate is too stable, it may lead to an excessively high hydrogenation barrier. We have studied the second catalytic step; the hydrogenation of alkenes, Scheme 4. The catalytic cycle of a metallylene including the oxidative addition of small molecules and the reductive elimination.