Synthesis and spectroscopic characterization of titanium pyridylanilido complexes as catalysts for the polymerization of 1,3-butadiene and isoprene

Abstract

A series of titanium(IV) complexes of general formula TiCl3[N,N-(pyridin-2-ylalkyl)anilido, TiCl3L, 8-13, were prepared by reactions of TiCl4 with substituted (pyridin-2-ylalkyl)anilines, LH, and characterized by analytical and spectroscopic methods. Compound 10 was obtained by using TiI4 as titanium precursor. In the case of LH = 2,6-diisopropyl(pyridin-2-ylmethyl)aniline, 1, and 2,6diisopropyl(pyridin-2-ylethyl)aniline, 2, the intermediate formation of TiCl4LH, 6-7, was detected, undergoing HCl elimination on heating to finally give 8 and 9. The products are not stable in coordinating solvents (thf, CH3CN). Ligand dissociation was observed from TiCl3(N,N-2,6diisopropyl(pyridin-2-ylmethyl)anilido, 8, resulting in the formation of Ti2OCl6(CH3CN)4 and 2-(2,6diisopropyl-phenylaminomethyl)pyridinium hexachlorotitanate. By reaction of TiCl3(thf)3 or TiI3 with 1 and 2 at ca 100 °C, the air sensitive derivatives TiCl2L, 14, and TiI2L, 15, were afforded.All titanium complexes were evaluated as catalysts for the polymerization of 1,3-butadiene and isoprene, in association with methylaluminoxane (MAO). The results indicate that the catalytic activity is strictly dependent on the nature of the ligands and the oxidation state of the metal, while the nature of the titanium complex has negligible influence on the selectivity.

Highly Stereoregular 1,3-Butadiene and Isoprene Polymers through Monoalkyl-N-Aryl-Substituted Iminopyridine Iron Complex-Based Catalysts: Synthesis and Characterization

“…2-Methyl(pyridin-2ylmethyl)aniline (L1), 2-methyl(pyridin-2-ylethyl)aniline (L2), 2isopropyl(pyridin-2-ylethyl)aniline (L3) 2-tert-butyl(pyridine-2ylmethyl)aniline (L4), and 2-tert-butyl(pyridine-2-ylethyl)aniline (L5) were synthesized according to the literature. 56 Elemental analysis was performed with a Perkin−Elmer CHN Analyzer 2400 Series. The Fourier Transform infrared-attenuated total reflectance (FTIR-ATR) spectra of the complexes were recorded using Bruker IFS 48 or Perkin−Elmer Spectrum One spectrophotometers equipped with a Thermo Spectra-Tech horizontal ATR connection and are given in Figures S1−S8.…”

“…MAO (Merck, 10 wt % solution in toluene), tetrachloroethane-d 2 (C 2 D 2 Cl 4 ) (>99.5% atom D), 2-pyridinecarboxaldehyde, 2-acetylpyridine, 2- iso -propylaniline, and 2-methylaniline were purchased from Merck and used as received. 2-Methyl­(pyridin-2-ylmethyl)­aniline ( L1) , 2-methyl­(pyridin-2-ylethyl)­aniline ( L2) , 2-isopropyl­(pyridin-2-ylethyl)­aniline ( L3 ) 2- tert -butyl­(pyridine-2-ylmethyl)­aniline ( L4) , and 2- tert -butyl­(pyridine-2-ylethyl)­aniline ( L5) were synthesized according to the literature …”

“…α-Anilinopyridine (L1−L5, Chart 1c) was synthesized via condensation with equimolar amine and 2acetyl-pyridine or 2-pyridine-carboxyldehyde, followed by reduction of iminopyridine by sodium borohydride (NaBH 4 ), as described in the literature. 56 The reactions of L1−L5 with iron chlorides (L/Fe molar ratio = 1) are strongly dependent on the oxidation state of the metal. The reaction with FeCl 2 to give pure Fe2-L1−Fe2-L5 (Chart 1c) requires refluxing the mixture to microcrystalline solids that are stable in air for a short time but need to be stored under an inert atmosphere.…”

Dienes Polymerization: Where We Are and What Lies Ahead

“…Thermally robust titanium(IV) and titanium(III) complexes of general formula TiX n L (X = Cl, I; n = 2, 3; L= (pyridin-2ylalkyl)aniline), in combination with MAO, provided active (up to 1680 kg polybutadiene (mol Ti) −1 h −1 and 37 kg polyisoprene (mol Ti) −1 h −1 ) but not very selective catalytic systems for the polymerization of 1,3-butadiene and isoprene: polybutadienes and polyisoprenes with a cis content of about 85% and 60% were obtained, respectively. 69 Predominantly cis-1,4-polybutadienes (cis content ≥80%) were also obtained with catalysts based on titanium complexes with ligands containing N and/or O as donor atoms (e.g., pyridine-imines, keto-imines, and bis-imines) 70,71 (Figure 5). Some complexes of Ti(II) and Ti(IV) with bidentate dialkylphosphines (e.g., TiCl 2 (dmpe) 2 , dmpe = 1,2-bis-(dimethylphosphino)ethane; TiCl 4 (dmpe) 2 ; TiCl 4 (depe) 2 , depe = 1,2-bis(diethylphosphino)ethane) were used in combination with MAO for the polymerization of butadiene.…”

“…Thermally robust titanium­(IV) and titanium­(III) complexes of general formula TiX n L (X = Cl, I; n = 2, 3; L= (pyridin-2-ylalkyl)­aniline), in combination with MAO, provided active (up to 1680 kg polybutadiene (mol Ti) −1 h –1 and 37 kg polyisoprene (mol Ti) −1 h –1 ) but not very selective catalytic systems for the polymerization of 1,3-butadiene and isoprene: polybutadienes and polyisoprenes with a cis content of about 85% and 60% were obtained, respectively …”