Well-defined phosphate yttrium dialkyl complexes for catalytic stereo-controllable 1,4-polymerization of isoprene

Living cis-1,4-Selective Polymerization of 1,3-Dienes by Enamino-Oxazolinate Rare-Earth Metal Complexes

“…Polymers derived from isoprene (IP) are used widely in the manufacturing of many industries, and synthetic cis -1,4-polyisoprene (PIP) is ordinarily regarded as an alternative to natural rubber due to its similar chemical composition and stereostructure. In this regard, the study on homogeneous catalytic systems that showed high cis -1,4-selectivity for IP (co)­polymerization has been intensively conducted and has made considerable progress in the last half century. − Till now, various well-defined rare-earth metal catalytic systems have been applied as amazing catalysts for generating highly cis -1,4-regular PIPs because of their distinguishingly high catalytic activity and efficiency. − ,− Among them, the rare-earth metal complexes bearing β-diketiminato ligands (Figure a) have been found to be efficient catalysts for IP polymerization due to their ease of preparation and high cis -1,4-selectivity (as high as 98.7%). , As β-diketiminato derivates, the anilido-oxazolinate ligands (Figure b) have also been applied in the rare-earth metal-catalyzed cis -1,4-selective polymerization of isoprene, generating polymers with high cis -1,4-regularity (up to 95.9%). , However, a lack of controllability was observed in the β-diketiminato and anilido-oxazolinate rare-earth-catalyzed IP polymerization, and the resultant PIP in all the cases had a rather broad molecular weight distribution, − despite other previously reported rare-earth metal catalytic systems also rarely exhibiting a living character accompanied with high cis -1,4-selectivity.…”