CHAPTER 5: Mechanistic Aspects of Living Radical Polymerization Mediated by Organometallic Complexes

The capabilities, limitations and future expectations for organometallic complexes in the mediation of living radical polymerizations (LRP) are briefly reviewed. Emphasis is placed on the illustrating the electronic, structural, kinetic and thermodynamic factors that contribute to obtaining LRP by reversible termination (RT) and degenerative transfer pathways using organometallic metallic living radical polymerization (OMRP). Mechanistic features of OMRP are primarily illustrated by using cobalt (IIII) porphyrin and organo-cobalt porphyrin complexes that played a central role in establishing guidelines for structural, thermodynamic and kinetic criteria to obtain OMRP by reversible termination and degenerative transfer pathways. The capability of cobalt acetylacetonate (Co(acac)2 ) to mediate the precise LRP of vinyl acetate (VA) illustrate how this exceptional property arises from the highly unusual set of structural, electronic and thermodynamic properties. Applications in polymeric materials synthesis where OMRP is the preferred or exclusive method are summarized.