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Chiral Fluorous Dialkoxy‐Diamino Zirconium Complexes: Synthesis and Use in Stereospecific Polymerization of 1‐Hexene
Author(s) -
Kirillov Evgueni,
Lavanant Laurent,
Thomas Christophe,
Roisnel Thierry,
Chi Yun,
Carpentier JeanFrançois
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600895
Subject(s) - diastereomer , chemistry , cationic polymerization , stereospecificity , polymerization , medicinal chemistry , octahedron , stereochemistry , toluene , nuclear magnetic resonance spectroscopy , zirconium , crystal structure , catalysis , polymer chemistry , crystallography , organic chemistry , polymer
New catalysts for the isospecific polymerization of 1‐hexene based on cationic zirconium complexes incorporating the tetradentate fluorous dialkoxy‐diamino ligands [OC(CF 3 ) 2 CH 2 N(Me)(CH 2 ) 2 N(Me)CH 2 C(CF 3 ) 2 O] 2− [(ON 2 NO) 2− ] and [OC(CF 3 ) 2 CH 2 N(Me)(1 R ,2 R ‐C 6 H 10 )N(Me)CH 2 C(CF 3 ) 2 O] 2− [(ON Cy NO) 2− ] have been developed. The chiral fluorous diamino‐diol [(ON Cy NO)H 2 , 2 ] was prepared by ring‐opening of the fluorinated oxirane (CF 3 ) 2 COC H 2 with ( R , R )‐ N,N′ ‐dimethyl‐1,2‐cyclohexanediamine. Proligand 2 reacts cleanly with [Zr(CH 2 Ph) 4 ] and [Ti(O i Pr) 4 ] precursors to give the corresponding dialkoxy complexes [Zr(CH 2 Ph) 2 (ON Cy NO)] ( 3 ) and [Ti(O i Pr) 2 (ON Cy NO)] ( 4 ), respectively. An X‐ray diffraction study revealed that 3 crystallizes as a 1:1 mixture of two diastereomers (Λ‐ 3 and Δ‐ 3 ), both of which adopt a distorted octahedral structure with trans ‐O, cis ‐N, and cis ‐CH 2 Ph ligands. The two diastereomers Λ‐ 3 and Δ‐ 3 adopt a C 2 ‐symmetric structure in toluene solution, as established by NMR spectroscopy. Cationic complexes [Zr(CH 2 Ph)(ON 2 NO)(THF) n ] + ( n =0, anion=[B(C 6 F 5 ) 4 ] − , 5 ; n =1, anion=[PhCH 2 B(C 6 F 5 ) 3 ] − , 6 ) and [Zr(CH 2 Ph)(ON Cy NO)(THF)] + [PhCH 2 B(C 6 F 5 ) 3 ] − ( 7 ) were generated from the neutral parent precursors [Zr(CH 2 Ph) 2 (ON 2 NO)] ( H ) and [Zr(CH 2 Ph) 2 (ON Cy NO)] ( 3 ), and their possible structures were determined on the basis of 1 H, 19 F, and 13 C NMR spectroscopy and DFT methods. The neutral zirconium complexes H and 3 (Λ‐ 3 /Δ‐ 3 mixture), when activated with B(C 6 F 5 ) 3 or [Ph 3 C] + [B(C 6 F 5 ) 4 ] − , catalyze the polymerization of 1‐hexene with overall activities of up to 4500 kg PH mol Zr −1 h −1 , to yield isotactic‐enriched (up to 74 % mmmm ) polymers with low‐to‐moderate molecular weights ( M w =4800–47 200) and monodisperse molecular‐weight distributions ( M w / M n =1.17–1.79).