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Synthesis and structures of (R)-cyclopentadienyl-binaphthoxy titanium(iv) complexes and catalytic properties for olefin polymerization†
Li Wang,Qiaolin Wu,Hao Xu,Ying Mu
Dalton Transactions Pub Date : 04/17/2012 00:00:00 , DOI:10.1039/C2DT12471H
Abstract

Two new chiral pre-ligands, (R)-3,3′-bis(tetramethylcyclopentadienyl)-2,2′-bismethoxy-1,1′-bisnaphthalene (1) and (R)-3-tetramethylcyclopentadienyl-2,2′-bismethoxy-1,1′-bisnaphthalene (2), were synthesized by reaction of (R)-3,3′-dilithium-2,2′-bismethoxy-1,1′-bisnaphthalene with 2,3,4,5-tetramethyl-2-cyclopentenone at room temperature. Treatment of the pre-ligands 1 and 2 with butyllithium and Me3SiCl first, and subsequently with TiCl4 (2 and 1 equiv for 1 and 2, respectively) afforded a binuclear complex (R)-3,3′-bis[(tetramethylcyclopentadienyl)trichlorotitanium]-2,2′-bismethoxy-1,1′-bisnaphthalene (3) and a mononuclear complex (R)-3-(tetramethylcyclopentadienyl)trichlorotitanium-2,2′-bismethoxy-1,1′-bisnaphthalene (4) in moderate yields. Complexes 3 and 4 were further converted into constrained geometry complexes (R)-1,1′-bis{2,2′-naphthoxy-3,3′-bis[(tetramethylcyclopentadienyl)dibromotitanium]} (5) and (R)-1-(2-naphthoxy)-1′-(2′-naphthol)-3-(tetramethylcyclopentadienyl)dibromotitanium (6) by treatment with BBr3. The pre-ligands 1 and 2 were characterized by 1H and 13C NMR and high resolution mass spectroscopy (HRMS), and the new titanium complexes 3–6 were characterized by 1H and 13C NMR and elemental analyses. Molecular structures of 4, 5, and 6 were determined by single-crystal X-ray diffraction analysis. Complexes 4, 5, and 6 all have a pseudo-octahedral coordination environment and adopt a three-legged piano stool geometry around the titanium atom in their solid state structures. When activated with AliBu3 and Ph3CB(C6F5)4, the chiral complexes 5 and 6 show moderate catalytic activities for propylene, 1-hexene, and 5-ethylidene-2-norbornene (ENB) polymerization and ethylene/1-hexene copolymerization. The polymers produced by the chiral 5/iBu3Al/Ph3CB(C6F5)4 catalyst system from the 1-hexene, and ENB polymerization and ethylene/1-hexene copolymerization with high comonomer contents exhibit optical activity.

Graphical abstract: Synthesis and structures of (R)-cyclopentadienyl-binaphthoxy titanium(iv) complexes and catalytic properties for olefin polymerization
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