Isospecific Polymerization of Halide- and Amino-Substituted Styrenes Using a Bis(phenolate) Titanium Catalyst

Isospecific polymerization of polar styrenes is a challenge of polymer science. Particularly challenging are monomers bearing electron-withdrawing substituents or bulky substituents. Here, we report the coordination polymerization of halide- and amino-functionalized styrenes including para-fluorostyrene (pFS), para-chlorostyrene (pClS), para-bromostyrene (pBrS), and para-(N,N-diethylamino)styrene (DMAS) using 2,2 '-sulfur-bridged bis(phenolate) titanium precursor (1). The combination of 1 and [Ph3C][B(C6F5)(4)] and (AlBu3)-Bu-i provides crystalline poly(pFS)s with perfect isotacticity (mmmm > 95%) and high molecular weights (<= 16.0 x 10(4) g mol(-1)). Upon activation with a large excess of DMAO, 1 reaches polymerization activity of 5.58 x 10(5) g mol(Ti)(-1) h(-1) producing isotactic poly(pFS)s featuring higher molecular weights (<= 39.6 x 10(4) g mol(-1)). The distinguished performance of the 1/DMAO system has been extended to the polymerization of pClS and pBrS, both usually involve halogen abstraction during the polymerization, to produce isotactic and high molecular weight (M-n = 32.2 x 10(4) vs. 13.7 x 10(4) g mol(-1)) polymers in good activities (2.18 x 10(5) vs. 1.31 x 10(5) g mol(Ti)(-1) h(-1)). Surprisingly, 1/DMAO is nearly inactive for DMAS polymerization, on contrary, the system 1/[Ph3C][B(C6F5)(4)]/(AlBu3)-Bu-i displays isoselectivity (mmmm > 95%) albeit in a moderate activity.