Thus far, we postulated that, next to benzophenone, a dimethyl malonate radical can also perform HAT from complex 1, forming cobalt(III) carbene radical complex 2. To further study this hypothesis, we turned to density functional theory (DFT) calculations to estimate the bond dissociation energies (BDEs) (Table ). The BDEs indicate whether it is energetically feasible to homolytically cleave the respective bond. The BDE of the Co-C bond in complex 1 is 33 kcal/mol, which is relatively low compared to 95 kcal/mol for the C-H bond in complex 1 (entries 1 and 2, respectively). Hence, the Co-C bond is most likely homolytically cleaved upon irradiation of visible light (390-500 nm ~ E = 73-57 kcal/mol), forming a dimethyl malonate radical and [Co II (TPP)], of which the latter is observed by NMR spectroscopy (see above). Dimethyl malonate has a BDE of 97 kcal/mol (entry 3), meaning that in its radical form, it is strong enough to abstract the hydrogen from the C-H bond in complex 1, resulting in the cobalt(III) carbene radical complex 2. According to these DFT calculations, the reactions in Figure are energetically feasible. Based on the above-mentioned results, the mechanism in Scheme 2 is proposed. After deprotonation of dimethyl malonate by KOtBu, the respective anion replaces the chloride atom, forming complex 1. From here, two pathways can occur: I) benzophenone can abstract the hydrogen atom, forming the desired cobalt(III) carbene radical complex 2. II) Alternatively, the Co-C bond is homolytically cleaved, resulting into [Co II (TPP)] and a dimethyl malonate radical, of which the latter can abstract a hydrogen atom from another molecule of complex 1. In presence of styrene, complex 2 reacts with the double bond, forming cyclopropane 3 as the product and [Co II (TPP)], which cannot interact with the anionic malonate and therefore ending the cycle. In absence of benzophenone, only a maximum yield of 5% can theoretically be achieved via pathway II, since two molecules of complex 1 are required to generate one molecule of radical complex 2. Hence, we believe that pathway I is dominant, because an average yield of 11% of cyclopropane 3 is observed when using 10 mol% [Co III (TPP)Cl].