Carrow et al. recently reported that, under visible light irradiation, T-shaped alkyl-Pd II complexes such as (P t Bu3)Pd II MeCl underwent homolysis, liberating alkyl radicals in addition to a Pd I metalloradical fragment which could be trapped by TEMPO. When studying the carbonylation of aryl halides, Arndtsen et al. found that irradiation of proposed intermediate (DPEPhos)Pd II (COAr)(Cl) by visible light produced the acyl chloride (via the acyl radical) and Pd 0 nearly quantitatively, a reaction that reversed in the dark. To our knowledge, direct homolysis of Pd II -Ar bonds under visible light-irradiation has not been reported. In our previous study investigating ground-state palladium chemistry, stoichiometric reactions of oxidative addition intermediates did not provide coupled products when using a ligand (dppf) that successfully promoted radical coupling from corresponding aryl halides, showing that the oxidative addition species are not intermediates in the ground-state radical coupling reactions. We now employed oxidative addition complexes in stoichiometric reactions to test for homolysis of the Pd II -Ar bond under visible light. Stoichiometric reactions were carried out using the cis-oxidative addition complexes (Dppf)Pd(xylyl)(I) 14a and (BINAP)Pd(xylyl)(I) 14b, as well as trans-complexes (PPh3)2Pd(xylyl)(I) 14c, (PCy3)2Pd(xylyl)(I) 14d and (P i Pr3)2Pd(xylyl)(I) 14e, all of which were simply prepared from Pd2dba3, ligand and 6. Under standard conditions, both cis-complexes 14a and 14b provided coupled products 7 and 8 in good yields relative to the starting complex, and importantly exhibited a ratio of 8:7 (Table , entries 1-2) that supported a radical mechanism. Trans-complex 14c also produced high yields, although with a slightly lower ratio of 8:7 (entry 3). Complexes bearing alkylphosphine ligands, 14d and 14e, produced coupled products in much lower yields in addition to significant quantities of reductive elimination product 6, but a ratio of 8:7 supporting aryl radical intermediates was maintained (entries 4-5). When deuterated benzene, C6D6, was employed, a large decrease in the yield of 8 and 9 was observed, accompanied by a significant increase in the yield of 7 (entries 6-8). Additionally, the proportion of 9 that is deuterated (deuterium incorporation 65.2% from 14a, 46.9% from 14b and 78.8% from 14c) is much higher than in catalytic reactions carried out in C6D6 (Table ) because the concentration of benzyl C-H groups is much lower. These results are consistent with homolysis of the Pd-Ar bond to form a m-xylyl radical (10). Interestingly, base could be excluded with little or no detriment to the reactions (entries 9-10).