Isospecific Polymerization of Methyl Methacrylate by Intramolecular Rare-Earth Metal Based Lewis Pairs

A series of cationic rare-earth aryloxide complexes,ie,,[LREOAr^(1)]^(+)[B(C_(6)F_(5))_(4)]^(-)(L=CH_(3)C(NAr)CHC(CH_(3))(NCH(R)CH_(2)PPh_(2));RE=Y,Lu;Ar'=2,6-tBU_(2)-C_(6)H_(3),2,6-(PhCMe_(2))_(2)-4-Me-C_(6)H_(2);Ar=2,6-iPr_(2)-C_(6)H_(3),2,6-(Ph_(2)CH)_(2)-4-iPr-C_(6)H_(2);R=H,CH_(3),iPr,Ph),were prepared and ap-plied to the Lewis pair polymerization of methyl methacrylate(MMA).The stereoregularity of the resulting PMMA was significantly affected by the R substituent on the pendant arm of the tridentate NNP ligand,and was found to increase with increase in the steric hindrance of R.