Highly active and removable ruthenium catalysts for transition-metal-catalyzed living radical polymerization: design of ligands and cocatalysts.
The systematic search and design of phosphine ligands (PR(3)) and amine cocatalysts resulted in obtaining pentamethyl-cyclopentadienyl (Cp*) ruthenium(II) phosphine complexes [RuCp*Cl(PR(3))(2)], which are highly active and removable catalysts, for transition-metal-catalyzed living radical polymerization of methyl methacrylate (MMA). The catalysts are conveniently prepared in situ from a tetrameric precursor [RuCp*(mu(3)-Cl)](4) and a selected phosphine (PR(3)). The combination of the meta-tolyl phosphine [P(m-Tol)(3)] ligand and a primary diamine cocatalyst [NH(2)(CH(2))(6)NH(2)] provides a highly active catalytic system with precision control of the molecular weight of the polymer. The high activity enables a low catalyst dose and a high turn-over frequency without deteriorating the controllability. A hydrophilic amine cocatalyst (amino alcohol) in place of the diamine, further forms an active and removable catalyst; simple treatment with acidic water gave colorless polymers visually free from metal residues (>97 % removal; <64 ppm).
Ouchi
Makoto
M
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan. ouchi@living.polym.kyoto-u.ac.jp
Ito
Makoto
M
Kamemoto
Satoshi
S
Sawamoto
Mitsuo
M