The addition of varying amounts of Co Pc into the reaction results in clear trends, which mirror those observed in Table . We propose that the reaction can be broken down into three distinct regimes which are related to the relative loadings of bpy Ni and Co Pc . Regime 1 occurs when the rate of radical formation and capture at (dtbbpy)Ni II (Ar)X is slow relative to the rate of decomposition of (dtbbpy)Ni II (Ar)X, which deleteriously consumes the aryl halide to produce biaryl and protodehalogenated products (Figure ). Further, unreacted alkyl halide remains after all of the aryl electrophile has been consumed (Entry 2). Regime 2 occurs when the rate of alkyl radical formation and capture at (dtbbpy)Ni II (Ar)X is optimal relative to the formation and decomposition of (dtbbpy)Ni II (Ar)X. In this regime, high product yields are observed and no unreacted starting material remains at the end of the reaction (Entries 3-6). Regime 3 occurs when alkyl radical formation is faster than the generation of (dtbbpy)Ni II (Ar)X, and, as a result, the alkyl radical decomposes before it can be trapped by Ni and unreacted aryl halide remains after the alkyl halide has been consumed (Entries 7 & 8). The same trends are also obtained when the loading of bpy