writer：Dongtao Liu, Yunjie Luo, Wei Gao and Dongmei Cui
keywords：organoborates; cationic complex; precursors; aluminum trialkyls; syndioselectivity
source：期刊
specific source：http://pubs.acs.org/doi/pdf/10.1021/om1000265
Issue time：2010年

The novel N-R-quinolinyl-8-amino ligands HL^1?5 (R = 2,6-Me₂C₆H₃ (HL¹), 2,4,6-Me₃C₆H₂ (HL²), 2,6-Et₂C₆H₃ (HL³), 2,6-ⁱPr₂C₆H₃ (HL⁴), C₆H₅ (HL⁵)) reacted with Sc(CH₂SiMe₃)₃(THF)₂ to afford the well-defined complexes (L^1?5)Sc(CH₂SiMe₃)₂(THF) (1?5), which were fully characterized by NMR spectral and X-ray diffraction analyses. Complexes 1?3 combined with organoborates to establish binary systems that exhibited high activity for the polymerization of styrene, while 4 was less active and 5 was almost inert. The cationic complex [L¹Sc(CH₂SiMe₃)(DME)₂][B(C₆F₅)₄] (6) was successfully isolated by treatment of 1 with [PhMe₂NH][B(C₆F₅)₄], and represents probably the structural model of the initiation active species. Remarkably, upon addition of aluminum trialkyls to the binary systems, distinguished improvement in catalytic performances was achieved, among which the ternary system 1/5AlⁱBu₃/[Ph₃C][B(C₆F₅)₄] displayed the highest activity (1.56 × 10⁶ g mol^?1 h^?1) and syndioselectivity (r = 0.94) via a chain-end control mechanism governed by the concerted steric effect of the ligand and the aluminum alkyls. This represents the first non-cyclopentadienyl stabilized rare-earth metal based catalyst showing both high activity and specific selectivity for the polymerization of styrene, which might shed new light on designing more efficient precursors and further investigation of the mechanism for this polymerization.