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A series of fluorenyl-based constrained-geometry-configuration (CGC) allyl-type rare earth metal monoalkyl complexes bearing the divalent anionic η 3 :η 1 - tert -butyl(dimethylfluorenylsilyl)amido (η 3 :η 1 -FluSiMe 2 N  t  Bu) ligand (η 3 :η 1 -FluSiMe 2 N  t  Bu)Ln(CH 2 SiMe 3 )(THF) 2 ( 1 - 3 ) have been synthesized via the alkane elimination reaction between the FluHSiMe 2 NH  t  Bu ligand and rare earth metal tri(trimethylsilylmethyl) complexes Ln(CH 2 SiMe 3 ) 3 (THF) n . Their structures are characterized by means of NMR spectrum, elemental analyses, and X-ray diffraction. These complexes 1 - 3 are isostructural and isomorphous, and each of them adopts a distorted-trigonal-bipyramidal configuration containing one η 3 :η 1 -FluSiMe 2 N  t  Bu ligand, one CH 2 SiMe 3 ligand, and two THF molecules. Unlike traditional CGC allyl-type rare earth metal complexes showing no or low activity and regio-/stereoselectivity in styrene or MMA polymerization, these complexes 1 - 3 exhibit high catalytic activities and/or high regio-/stereoselectivities in the cis -1,4-polymerization of isoprene and myrcene or in the syndiotactic polymerization of styrene under the aid of different activators (borate or borane) and AlR 3 . The in situ 1 H NMR spectra suggest that the exchanges of chelating ligands such as alkyl groups and divalent anionic η 3 :η 1 -FluSiMe 2 N  t  Bu ligands between rare earth metal centers and Al centers result in the formation of a heterobimetallic tetraalkylaluminate complex R 2 Al( μ -R) 2 Ln(R)( μ -R) 2 AlR 2 , which is activated by activators to form a divalent cationic species [Ln( μ -R) 2 AlR 2 ] 2+ as a catalytically active species in the coordination-insertion polymerization of olefins.

polymers

Unprecedentedly High Activity and/or High Regio-/Stereoselectivity of Fluorenyl-Based CGC Allyl-Type η3:η1-tert-Butyl(dimethylfluorenylsilyl)amido Ligated Rare Earth Metal Monoalkyl Complexes in Olefin Polymerization