Side-Arm Assisted Anilido-Imine Based Rare-Earth Metal Complexes for Isoprene Stereoselective Polymerization
作者：Yi Wu , Xinli Liu*, and Dongmei Cui*
关键字：rare-earth metal catalyst， polyisoprene，stereoselectivity
论文来源：期刊
具体来源：Molecules 2021, 26, 4154
发表时间：2021年
Anilido-imine ligands o-C6H4(NHAr1)(CH=NAr2), in which Ar1 is 2,6-diisopropylbenzyl
group and Ar2 contains fluorine (HL1) or methoxyl (HL2) group on ortho-position of phenyl substituent,were synthesized for constructing rare-earth metals based complexes of 1a–1c (HL1 based Sc, Lu, Y) and 2a–2c (HL2 based Sc, Lu, Y). Based on their NMR spectra and X-ray single-crystal structures, the side-arm group of -F and -OMe is identified to chelate to the corresponding central metal. The twisted angles between two planes formed by chelated heteroatoms (N, N, F for HL1 and N, N, O for HL2) are observed, in which the largest dihedral angle (53.3 ) for HL1-Y and the smallest dihedral angle (44.32 ) for HL2-Sc are detected. After being activated by Ali Bu3 and [Ph3C][B(C6F5)4], these catalysts showed great activity for isoprene polymerization. Bearing the same ligand HL1, smaller scandium based complex 1a and middle size of lutetium based 1b provided lower cis-1,4-selectivity (57.3% and 64.2%), larger yttrium complex 1c displayed high cis-1,4-selectivity (84%). Chelating by crowded HL2, small size of scandium complex 2a provided impressive trans-1,4- selectivity (93.0%), middle lutetium based 2b displayed non-selectivity and larger yttrium complex 2c showed clear cis-1,4 selectivity (83.3%). Moreover, 2a/Ali Bu3 system showed the quasi-living chain transfer capability.