To gain further insight into the reaction mechanism, we explored a CEC reaction between the activated substrates phenyl iodide and benzyl chloride (Table ). In the absence of Co Pc , the reaction proceeded in 40% yield (Entry 1). Significant quantities of benzyl chloride were still present at the end of the reaction, showing that alkyl halide consumption is slow relative to aryl halide consumption. Notably, Ni is able to engage the alkyl electrophile to promote catalysis in the absence of Co Pc with the highly activated benzyl chloride substrate. In contrast, when reactions are performed with weakly activated alkyl halides, such as primary alkyl bromides, no product formation is observed in the absence of Co Pc (see SI). These observations align with our hypothesis and suggest that bpy Ni primarily activates the aryl electrophile, while Co Pc primarily activates the alkyl electrophile.