A DFT analysis of the reaction of bpyNiEt(2) with ArN3 was performed for para-tolyl-azide (Ar = pTol), 3,5-dimethyl-phenyl-azide (Ar = mXy) and ortho-tolyl-azide (Ar = oTol), and mesityl-azide (MesN(3)). Of particular interest were the different products obtained for the latter (ethylene, butane, azomesitylene, mesityl-ethylamine, etc.) versus the other reagents, i.e., (bpyNi(N(Ar)Et)(Et)). Calculated thermodynamics and kinetics for metal-free reactions did not differentiate MesN(3) from the other aryl azides. Once (2)bpyNiEt(center dot) was generated via bond homolysis, formation of ethylene by beta-H elimination was facile, as was formation of nickel-imidyl (NR-center dot) intermediates by reaction of ArN3 with bpyNiEtx (x = 0-2). On the basis of computed energetics, three reactions of bpyNiEt(2) were proposed to compete: Ni-C bond homolysis, reductive elimination of butane, and nucleophilic attack (NA) by ArN3. Inspection of their temperature dependence suggested that NA and Ni-Et bond homolysis dominated at lower and higher temperatures, respectively. Calculated Ni-N and Ni-C bond dissociation free energies (BDFEs) suggested the role of radical pathways in discriminating bpyNiEt(2)/ArN3 reactions, and implied that the concentration of radicals such as aminyl (ArN center dot(Et)), (2)bpyNiEt(center dot), and Et-center dot will be greatest for MesN(3).