Toward structural and mechanistic understanding of transition metal-catalyzed atom transfer radical processes

Structural and mechanistic aspects of transition metal catalyzed atom transfer radical polymerization (ATRP) were discussed. Structures of Cu-I and Cu-II active ATRP catalysts were investigated using various spectroscopic techniques and were found to be dependent on the nature of the complexing ligand, solvent and temperature. The overall equilibrium constant for ATRP was correlated with the redox potentials of Cu-I complexes with nitrogen based ligands and equilibrium constant for halogen dissociation from the corresponding Cu-II-X complexes. Additionally, various techniques to measure the kinetics of elementary reactions in the ATRP such as activation, deactivation and initiation rate constants were presented.