Summary: The effect of [L]/[CuI] ratio, ligand, the choice of solvent and temperature on the activation rate constants in ATRP with catalyst complexes formed with two pyridylmethanimine ligands [PMI, i.e., N-propyl-pyridylmethanimine (NPPMI) and N-octyl-pyridylmethanimine (NOPMI)] were studied. Maximal values for the apparent rate constants were observed at an [L]/[CuI] ratio of ∼2/1 and 1/1 in polar and nonpolar solvents, respectively. This is similar to the results obtained with the CuI/bpy system and was attributed to the formation of [CuI/L2]+Br− and [CuI/L2]+CuIBr species. The CuI/NPPMI system was only soluble in polar reaction media; however, the CuI/NOPMI complex was soluble in both polar and less polar reaction media. The activation rate constants increased with increasing temperature and the value of activation energy (Ea) for CuI/NPPMI in the activation process was 58.1 kJ · M−1 · K−1.
Arrhenius plot of ln ka versus 1/T for the activation process for NPPMI and bpy in acetonitrile; [CuIBr/NPPMI2]0 ([CuIBr/bpy2]0)/[EtBriB]0/[TEMPO]0/[TCB]0 = 20/1/10/2 × 10−3M.