In DMF, the NiBr2•glyme is proposed to form the octahedral NiBr2(DMF)4 as the dominant species in solution based on published spectra of related species (see SI, Section 2.1). As a Ni:OMebpy ratio of 1:1 is approached, the characteristic broad absorption bands of NiBr2(DMF)4 with maxima at ~420, ~710, ~760, and ~1250 nm weaken in intensity, while new signals appear with maxima at ~650, ~1020, and ~1120 nm. We assign this spectral change to the first addition of OMebpy to the Ni center to form NiBr2(DMF)2(OMebpy). Next, as the 1:1 ratio is exceeded and 1:2 is approached, these signals which just formed die away, concomitant with the rise of new signals at ~590, ~800, and ~950 nm that we assign to NiBr2(OMebpy)2. Finally, signals corresponding to NiBr2(OMebpy)2 disappear as the ratio of 1:3 is exceeded, and signals with maxima at ~530, ~780, and ~860 nm assigned to [Ni(OMebpy)3]Br2 appear. Notably, these signals closely match those observed in the literature for [Ni(bpy)3]BF4 (bpy = 2,2'-bipyridine), supporting our assignment. To precisely determine the ratio of each species in the Ni-OMebpy mixture, the titration data was fit to four variants (flavors) of a 1:3 (metal:ligand or host:guest) binding model. This fit was performed using a Matlab code based on the analytical solution to the system of equations for the 1:3 equilibria, 10 similar to that described in an NMR study on a 3:1 complexation of a bis-antimony receptor with halide anions. A global analysis using the UV-vis binding isotherms from λ = 450-1200 nm was performed (See SI for details, Section 2.2). Comparing how the variants (flavors) of the 1:3 binding model fitted the data showed that the "full" 1:3 model which assumes both i) cooperativity and ii) that the 1:1, 1:2, and 1:3 stepwise complexes have distinct spectra, gave a significantly better fit to the data.