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

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 Me(3)SiCl first, and subsequently with TiCl(4) (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 BBr(3). The pre-ligands 1 and 2 were characterized by (1)H and (13)C NMR and high resolution mass spectroscopy (HRMS), and the new titanium complexes 3-6 were characterized by (1)H and (13)C 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 Al(i)Bu(3) and Ph(3)CB(C(6)F(5))(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/(i)Bu(3)Al/Ph(3)CB(C(6)F(5))(4) catalyst system from the 1-hexene, and ENB polymerization and ethylene/1-hexene copolymerization with high comonomer contents exhibit optical activity.

Shedding light on the poly(5‐ethylidene‐2‐norbornene) microstructural differences: Skeleton rearrangements during polymerization

“…2,19 The negligible signals at 6-6.2 ppm (Figure 7, region (I)) confirmed the 6,8-enchainment of ENB into the polymer backbone. 17 It is quite clear that the ENB cationic polymerization data obtained in the presence of an AlEt 2 Cl-activated vanadium-based catalyst are in complete agreement with these results. 23 The characteristic signals that are assignable to unsaturated moieties (2.4-2.8 and 5-6.2 ppm) for P(ENB-B) have been previously shown to disappear following the chemical functionalization.…”

“…The peaks at 5.5–6 ppm region (endocyclic double bonds) feature signals corresponding to cyclopentenyl (cationic polymerization) and cyclohexenyl moiety (vinyl‐addition/RO) 2,19 . The negligible signals at 6–6.2 ppm (Figure 7, region (I)) confirmed the 6,8‐enchainment of ENB into the polymer backbone 17 . It is quite clear that the ENB cationic polymerization data obtained in the presence of an AlEt 2 Cl‐activated vanadium‐based catalyst are in complete agreement with these results 23 .…”

“…Additionally, this cooperative effect has been illustrated to significantly influence the chain transfer and enchainment reactions, leading to the production of different chain microstructures 15 . This outperformance in the catalyst activity as well as distinguishing features in tailoring chain structures are also the case for the polymerization of cyclic olefins by binuclear nickel catalysts (BNC) and binuclear titanium catalysts (BTC) 16,17 . Similar to parent NB, ENB can be polymerized through cationic, addition, and ROMP polymerization pathways (Scheme 3).…”

“…15 This outperformance in the catalyst activity as well as distinguishing features in tailoring chain structures are also the case for the polymerization of cyclic olefins by binuclear nickel catalysts (BNC) and binuclear titanium catalysts (BTC). 16,17 Similar to parent NB, ENB can be polymerized through cationic, addition, and ROMP polymerization pathways (Scheme 3). 18,19 Interestingly, as illustrated in Scheme 3, in the presence of cationic initiators, ENB would undergo structural rearrangements, delivering cationic P(ENB), which is distinctly different from cationic P(NB) (Scheme 1).…”

Asymmetric binuclear metallocene complexes and their application for olefin polymerization

“…Nohn group induced the control of both molecular weight and comonomer response of ethylene polymerization via utilization of alkyl branches at the para‐xylene bridge of new dinuclear constrained geometry catalysts. Wang et al synthesized the (R)‐cyclopentadienyl‐binaphthoxy titanium(IV) complexes and used for ethylene/ 1‐hexene copolymerization and found that the high comonomer contents exhibit optical activity.…”