This Review aims at a comprehensive overview on the recent stereospecific control polymerizations by group 3 metal complexes based catalytic systems in combination with aluminum alkyls and organoborates etc. co‐catalysts. The involved monomers include styrene and substituted styrenes, and the conjugated dienes like isoprene and butadiene, and their derivatives. The syndio‐ and iso‐selective polymerizations of styrene, unmasked polar styrenes and the copolymerizations of styrene with conjugated dienes and polar styrenes are summarized. The factors of influencing the catalytic activity and selectivity are discussed. The regio‐ and stereo‐ selective polymerizations of conjugated dienes, polar diene derivatives and their copolymerizations are reviewed. The relationship between catalyst structure and polymerization activity, the mechanism of stereo‐selective polymerization and the influence of different cocatalysts are discussed.
Rare-earth metal complexes (Flu-CH -Py)Ln(CH SiMe ) (THF) (Ln=Sc(1), Lu(2), Tm(3), Y(4) and Gd(5)), upon the activation of [Ph C][B(C F ) ] and Al Bu , were employed to catalyze the polymerization of allene derivatives under mild conditions. The Gd, Y, Tm, Lu metal based precursors exhibited distinguished 2,3-selectivity (>99.9 %) for phenylallene (PA) polymerization, whereas the smallest Sc metal based precursor showed a moderate 2,3-selectivity. The activity increased with the central metal size following the trend of Gd(5)>Tm(4)>Y(3)>Lu(2)>Sc(1). Moreover, Gd(5) also realized the purely 2,3-selective polymerizations of polar or nonpolar allene derivatives, para-methylphenylallene, para-flourophenylallene and para-methoxyphenylallene, regardless of electron-donating or -withdrawing substituents. Owing to the highly regular backbones, these polymers (except PPA) were crystalline, thus being the first crystalline polymers based on allene derivatives.
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