Living 3,4‐(Co)Polymerization of Isoprene/Myrcene and One‐Pot Synthesis of a Polyisoprene Blend Catalyzed by Binuclear Rare‐Earth Metal Amidinate Complexes

Mononuclear amidinate yttrium complex C4H9C(NR)2Y(o‐CH2C6H4NMe2)2 (R=2,6‐iPr2C6H3) and a series of binuclear rare‐earth metal complexes bearing a bridged amidinate ligand [(RN)2C(CH2)4C(NR)2][RE{CH2C6H4(o‐NMe2)}2]2 (R=2,6‐iPr2C6H3, RE=Y, Lu, Sc) were synthesized and fully characterized. The catalytic behavior of these complexes for (co)polymerization of conjugated dienes such as isoprene and myrcene in the presence of co‐catalyst [Ph3C][B(C6F5)4] was investigated. These catalytic systems show impressively high activity and 3,4‐regioselectivity in living (co)polymerization. The binuclear bridged amidinate yttrium catalytic system not only exhibits the highest activity among the reported catalytic systems for 3,4‐polymerization of isoprene but also allows the steady polymerization in a living manner from −20 to 80 °C. Compared with the dramatic drop of 3,4‐selectivity for the mononuclear analogue, the binuclear catalytic system still shows moderate 3,4‐selectivity at 80 °C. Moreover, a facile one‐pot synthetic strategy for a polymer blend containing 3,4‐ and 1,4‐polyisoprene (PIP) was established through the in situ modification of the active amidinate yttrium species by addition of an excess amount of AlMe3. Amidinate complexes, a mononuclear amidinate yttrium complex and a series of binuclear rare‐earth metal complexes, have been synthesized. They are excellent catalyst precursors for living (co)polymerization of conjugated dienes such as isoprene and myrcene. In contrast to the mononuclear analogue, a synergistic effect of the binuclear complex has been observed. Moreover, a polymer blend of 3,4‐ and 1,4‐polyisoprene (PIP) was obtained through one‐pot synthesis.