While K1 agrees well with literature values given for bpy in H2O and mixed alcohol/aqueous solutions, 25 K2 and K3 are several orders of magnitude higher here than in those systems. This difference could be due to the electron rich nature of OMebpy as compared with bpy and/or the difference in binding strength of DMF as compared with protic solvents in terms of coordination to Ni. Given that DMF and other polar, aprotic solvents are often used in dual Ni photocatalysis, we expect these results to be widely applicable. In addition, the binding model allowed calculation of the exact concentrations of each species at relevant Ni:OMebpy ratios for catalysis (Fig. ). Importantly, at the 1:2 ratio used in our system, the dominant species in the Ni-bipyridine mixture is NiBr2(OMebpy)2 at 78.5%, with 10.9% [Ni(OMebpy)3]Br2 and NiBr2(DMF)2(OMebpy) (10.2%), while only 0.4% of the starting NiBr2(DMF)4 remains. Control experiments confirm that the aryl halide, alcohol, and Ir(ppy)3 do not significantly affect the UV-vis signal (See SI, Fig. ) and thus are unlikely to affect the speciation as determined above. Importantly, the alcohol does not bind to the Ni center at this stage, consistent with our hypothesis of transmetalation occurring at Ni(III) as detailed below.