We hypothesized that a cobalt(III) carbene radical complex might be formed after HAT from complex 1. To observe this carbene radical complex, we used continuous wave X-band EPR spectroscopy at 40 K (Figure ). Complex 1 was formed in situ by mixing [Co III (TPP)Cl], dimethyl malonate and KOtBu in toluene-d8. The solution was filtered and added to benzophenone inside a quartz tube. Next, the EPR sample was irradiated with 370 nm (43 W) at room temperature, before freezing the sample immediately. Figure shows the EPR signal obtained after irradiating the sample with light (black line). The signal can be assigned to two species: firstly, it contains a carbon centered radical that is attached to a cobalt porphyrin, of which the simulated spectrum is depicted below (pink line). The signal corresponds to the previously reported cobalt(III) carbene radical complex (2) (Figure ). Secondly, the obtained experimental spectrum also contains features of [Co II (TPP)] (grey line). Under dark conditions, no signal was observed: neither complex 2 nor [Co II (TPP)] (see supporting information, Figure ). These results indicate that [Co II (TPP)] is formed from complex 1 upon irradiation of light. To further investigate the reaction, benzophenone was excluded from the reaction mixture as a control experiment. Again, the in situ formed complex 1 was irradiated with light, before measuring the EPR spectrum. Figure shows the EPR spectra with (black) and without (blue) benzophenone in the reaction mixture. The same signal, although less intense, was observed when benzophenone was not present in the sample. This demonstrates that the cobalt(III) carbene radical complex 2 is also formed without a HAT reagent, only in lower concentrations.