Chiral fluorous dialkoxy-diamino zirconium complexes: Synthesis and use in stereospecific polymerization of 1-hexene

Abstract

New catalysts for the isospecific polymerization of 1-hexene based on cationic zirconium complexes incorporating the tetradentate fluorous dialkoxy-diamino ligands [OC(CF3)2CH2N(Me) (CH2)2N(Me)CH2C(CF3) 2O]2[(ON2NO)2-] and [OC(CF 3)2CH2N(Me)(1R,2R-C6,H 10)N(Me)CH2C(CF3)2O]2- [(ONCyNO)2-] have been developed. The chiral fluorous diamino-diol [(ONCyNO)H2, 2] was prepared by ring-opening of the fluorinated oxirane (CF3)2COCH2 with (R,R)-N,N′-dimethyl-1,2-cyclohexanediamine. Proligand 2 reacts cleanly with [Zr(CH2Ph)4] and [Ti(OiPr)4] precursors to give the corresponding dialkoxy complexes [Zr(CH2Ph) 2(ONCyNO)] (3) and [Ti(OiPr)2(ON CyNO)] (4), respec tively. An X-ray diffraction study revealed that 3 crystallizes as a 1:1 mixture of two diastereomers (Λ-3 and Δ3), both of which adopt a distorted octahedral structure with trans-O, cis-N, and cis-CH2Ph ligands. The two diastereomers Λ-3 and Δ-3 adopt a C2-symmetric structure in toluene solution, as established by NMR spectroscopy. Cationic complexes [Zr(CH2Ph)(ON 2NO)(THF)n]+ (n = 0, anion = [B(C 6F5)4]-, 5; n = 1, anion = [PhCH2B(C6F5)3]-, 6) and [Zr(CH2Ph)(ONCyNO)(THF)]+ [PhCH 2B(C6F5)3]- (7) were generatedfrom the neutral parent precursors [Zr(CH2Ph) 2(ON2NO)] (H) and [Zr(CH2Ph) 2(ONCyNO)] (3), and their possible structures were determined on the basis of 1H, 19F, and 13C NMR spectroscopy and DFT methods. The neutral zirconium complexes H and 3 (Λ3/Δ-3 mixture), when activated with B-(C6F 5)3 or [Ph3C] + [B(C 6F5)4]-, catalyze the polymerization of 1-hexene with overall activities of up to 4500 kg PH mol Zr lh-1, to yield isotactic-enriched (up to 74% mmmm) polymers with low-to-moderate molecular weights (Mw = 4800-47200) and monodisperse molecular-weight distributions (Mw/Mn = 1.17-1.79). © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.