Highly Cis-1,4-Polymerization Of Isoprene Catalyzed By Cationic Rare Earth Metal Catalyst Bearing CCC-Bis（NHC）—pincer Ligand

The development of environmentally friendly, air-stable, and highly efficient metal catalysts is of practical importance in organic chemistry and catalytic chemistry. In recent years, industrial production caused exponential growth in the demand for rubber led inadequation of natural rubber production seriously. As one species of the best alternate for natural rubber, the synthesis of cis-1,4-polymerization of isoprene efficiently has attracted great attention for chemists at home and abroad. N-heterocyclic carbene ligands(NHCs), which have excellent properties including the electron-rich nature, easy of synthesis and environmentally friendly, have been widely used in the field of organometallic chemistry. We synthetized a series of CCC-bis(NHC) pincer ligated rare-earth metal catalysts, which were characterized by NMR and X-ray single crystal diffraction. All the complexes could polymerize isoprene in the presence of MAO or MMAO or excess Borate or AlR3(R=Me, iBu)/Borate, the activity reached 1.506×103 g of PIP(mol of Ln)-1 h-1. Promoted by the outstanding properties like easily prepared, stabilization, and high activity for selectively isoprene polymerization, the CCC-bis(NHC) pincer lanthanide complexes had huge industrial application potential. The scandium compound CCC-bis(NHC) pincer Sc(CH2SiMe3)[N(SiMe3)2], especially, exhibited high stereoselectivity in the polymerization of isoprene. The cis-1,4-selective can be up to 97%.