bond, which occurs with simultaneous making of two M-H s-bonds and change in the formal oxidaOon state at the metal from M to M 2+ (Figure ). Similar processes can be found in textbook descripOons of mechanisms for hydrosilylaOon, hydroboraOon, isomerisaOon, cross-coupling, hydroformylaOon, and carbonylaOon. The descripOon of this process as "oxidaOve" has an implicaOon for the electronic structure of the products. In the case of dihydrogen, the inference is that the resultant M d+ -H d-bonds are polarised such that the electron density is located primarily on the hydrogen atom. While a formalism, the descripOon is both intuiOve, as most metal elements are less electronegaOvite than hydrogen, and useful, as it suggests a nucleophilic role of the hydrogen sites commonly involved in onwards steps (e.g. migratory inserOon). A philosophical quesOon arises: if electron density in the M-H bond is shared evenly between the metal and hydrogen atoms should the processes sOll be considered to be oxidaOve? Moreover, if the polarity of this bond is reversed M d--H d+ , would it be more suitable to describe this as a reducOve addiOon from the perspecOve of the metal site? In this paper, we describe the addiOon Cp*ZnZnCp* to a series of main group carbene analogues, including a silyene (Si), gallylene (Ga), and aluminylene (Al) compounds. The Zn-Zn bond of Cp*ZnZnCp* can be considered to be isolobal to the H-H bond, with s and s* molecular orbitals constructed from overlap of 4s-4s atomic orbitals rather than 1s-1s (Figure ). Previous studies have shown that Cp*ZnZnCp* reacts with transiOon metal complexes to form addiOon products. In the current case, the addiOon reacOons involve complete breaking of the Zn-Zn bond and construcOon of two new Si-Zn, Ga-Zn or Al-Zn bonds resulOng in an increase in the coordinaOon number of the main group centre from two to four. In the case of the gallylene, the process is reversible with both addiOon and eliminaOon accessible under ambient condiOons. DFT calculaOons and preliminary reacOvity are consistent with the Al d--Zn d+ , Ga d--Zn d+ and Si d--Zn d+ bonds being polarised such that the balance of electron density is located on the main group element. The findings imply that these reacOons could be described as reducOve addiOon processes at the main group centre. Our results challenge the preconcepOon regarding addiOon reacOons at metal centres, hinOng rather than being universally oxidaOve there is a likely a conOnuum of redox outcomes spanning reducOve, neutral, and oxidaOve, with a dependence of the precise nature of the metal centres and substrates involved.