Highly syndioselective coordination (co)polymerization of isopropenylstyrene

Coordination (co)polymerization of para-isopropenylstyrene (pIPSt) and meta-isopropenylstyrene (mIPSt), initiated by scandium (Sc) based catalysts, afforded new type of products, bearing pendant isopropenyl groups with perfect syndiotacity (rrrr > 99%). Sc catalysts demonstrated overwhelming chemoselectivity towards the vinyl group over the isopropenyl moiety of isopropenylstyrene. Compared to the constrained-geometry Sc catalysts, having electron-donating pyridyl methylene fluorenyl ligands FluCH(2)Py (1, Flu = C13H8; 2, Flu = 2,7-(Bu2C13H6)-Bu-t, Py = C5H5N), the half-sandwich Sc catalysts containing electron-withdrawing substituents [3, C13H8SiMe3Sc(CH2SiMe3)(2)(THF); 4, C5Me4PhSc(CH2C6H4NMe2-o)(2)] showed much higher catalytic activity under identical conditions. The activity of 4 could be over 2164 kg mol(Sc)(-1) h(-1) at room temperature at a lower monomer concentration (1 mol L-1). Moreover, copolymerization of pIPSt and styrene (St) proceeded fluently in a pathway close to ideal copolymerization, with closely matched monomer reactivity ratios: r(pIPSt) = 1.05, r(St) = 0.83. Therefore, a series of statically random copolymers with pendant unsaturated olefinic groups, ranging from 5% to 90%, were accessed. These pendant isopropenyl groups could be readily converted into epoxide and bromide moieties at mild reaction conditions.