CO2, NO2, and SO2 can be activated in silico with tailor-made light atom tripodal ligand systems carrying particular numbers of Lewis acidic and basic sites in specific relative orientations. In the calculated EO2-adducts (E=C, N, S), considerable E−O bond elongations of 0.1–0.3 Å, decreasing the E=O double bond character, and O−E−O angle alterations, approaching tetrahedral geometry, activate the donor acceptor complexes towards reduction with BH4−. The lone pairs of the P atoms thereby serve as donors towards the central element, C, N, or S, whereas the electron deficient B atoms serve as acceptors. The charge redistribution within the EO2 complex was monitored by a variety of DFT-derived real-space bonding indicators (RSBIs) including bond topologies, non-covalent contact patches, and electron pair basins. For one CO2-complex, the reduction towards methanol and water was conducted via stepwise addition of H− and H+. The most critical steps are the initial CO2 uptake due to potential quenching of the ligand systems in their active state, increasing the kinetic barrier, and the release of methanol and water from the ligand system due to potential ligand poisoning. Unbeneficial side reactions in the stepwise reduction and protonation have to be considered.
