A tungsten alkoxy scorpionate shows activity in the electrocatalytic reductive dehalogenation of pentachloroethane and trichloroethylene owing to the formation of hydrogen and halogen bonded adducts with the substrates, which is further reinforced by dispersive interactions. The ensuing proximity between the substrate molecule and the metal centre promotes dechlorination in a concerted process. Two-electron reduction of pentachloroethane yields trichloroethylene that undergoes further, non-catalysed, reactions that ultimately give acetylenes. Interestingly, pentachloroethane proved to be a highly efficient proton donor for the transient anions, in extremely exothermic and rapid proton transfer concerted with chloride anion abstraction, which yields perchloroethylene. The total process and the mechanism thereof were verified based on DFT and coupled cluster (CC) calculations. The calculations evaluated feasibility of various pathways in the mechanism. Standard redox potentials for the environmentally relevant species, participating in the studied reactions, were accurately computed employing the explicitly correlated CCSD(T)-F12 method that provides an improved C-Cl bond energy, of essential importance to the dissociative potentials.