Metal alkoxides as additives for ruthenium(II)-catalyzed living radical polymerization

Effects of additives (metal alkoxides and halides) were investigated in the RuCl2(PPh3)(3)-catalyzed living radical polymerization of methyl methacryl ate (MMA) in toluene at 80 degrees C. While the MMA polymerization with the RuCl2(PPh3)(3)/CCl4 system (CCl4: initiator) is very slow and produces pol ymers with broad molecular weight distributions (MWDs), addition of metal a lkoxides, such as Al(Oi-Pr)(3), Ti(Oi-Pr)(4), and Sn(Oi-Pr)(4), accelerated the polymerization to produce polymers with controlled molecular weights a nd narrow MWDs. Metal chlorides such as SnCl4 and TiCl4 were not effective additives. According to NMR and cyclic voltammetric analyses, Al(Oi-Pr)a do es not interact with monomer or the polymer termini (similar to similar to similar to C-Cl and similar to similar to similar to C-. radicals) but inte racts with the ruthenium complex, or more likely, its higher oxidation stat e Ru(III) species.