Titanium Tetrachloride Catalyst Research Articles

The Use of the Titanium Tetrachloride (Ticl4) Catalysts as a Reagent for Organic Synthesis

Abstract: TiCl4 is a widely utilized reagent in organic synthesis, often functioning through Lewis’s acid-promoted transformations. This review explores the potential for TiCl4 to catalyse various examples, adhering to the classic catalyst definition and allowing for the use of sub-stoichiometric quantities of the catalyst relative to the substrate. The use of metal catalysts in organic synthesis has witnessed a surge in interest due to their ability to facilitate a wide range of chemical reactions. This review article highlights the significance of titanium metal catalysts via comparison with other metal catalysts like Pd [NO3]2, IrO4, Au/Fe2O3, SnCl2, and AlCl3. Among these catalysts, titanium tetrachloride (TiCl4) has gained considerable popularity for its cost-effectiveness, eco-friendliness, enhancing reaction efficiency, and ability to accelerate reactions while reducing reaction times. This comparison helps in determining the most suitable catalyst for different chemical processes, considering efficiency, safety, and economic factors. TiCl4 operates as a non-consumable catalyst, allowing for the use of sub-stoichiometric quantities relative to the substrate. This review discusses TiCl4's applications, efficiency, and mechanisms in organic synthesis. It distinguishes itself by presenting new applications and comparative efficiencies of TiCl4, delving into detailed reaction mechanisms, and discussing its environmental, economic, and safety aspects. TiCl4's role in pivotal chemical reactions, such as Friedel-Crafts acylation and alkylation, epoxidation, cyclization, Mannich reactions, Suzuki-Miyaura reactions, Pechmann condensation, Knoevenagel condensation, anti-Markovnikov hydration, pinacol coupling, and Diels-Alder reactions. These reactions have led to the synthesis of biologically active compounds like zolmitriptan, ropinirole, risperidone, and rivastigmine. TiCl4-catalyzed reactions are characterized by their mild conditions, high efficiency, and selectivity, making them an attractive choice for modern organic cyclic, acyclic, and heterocyclic synthesis.

Selective C-C Bond Scission of Ketones via Visible-Light-Mediated Cerium Catalysis

Summary Here, we report a general catalytic manifold for the selective C–C bond scission of ketones via the exploitation of the ligand-to-metal charge transfer (LMCT) excitation mode. Through a cooperative utilization of Lewis acid catalysis and LMCT catalysis, the C–C bond of ketones could be selectively and effectively cleaved, enabling the installation of different functionalities at each carbon of the cleaved C–C bond through a sequential and orthogonal manner. This reaction manifold serves as a photocatalytic alternative to the Norrish type I reaction with the combination of visible light and inexpensive cerium salts. Under operationally simple conditions, a wide range of acyclic and cyclic ketones, from simple strained cyclobutanones to complex androsterone with less strained cyclopentanone moiety, could be successfully transformed into versatile chemical building blocks.

Surface-Initiated Polymerization with Poly(n-hexylisocyanate) to Covalently Functionalize Silica Nanoparticles.

New methods are needed for covalent functionalization of nanoparticles-surface with organic polymer coronas to generate polymeric nanocomposite in a controlled manner. Here we report the use of a surface-initiated polymerization approach, mediated by titanium (IV) catalysis, to grow poly(n-hexylisocyanate) chains from silica surface. Two pathways were used to generate the interfacing in these nano-hybrids. In the first one, the nanoparticles was "seeded" with SiCl4, followed by reaction with 1,6-hexanediol to form hydroxyl groups attached directly to the surface via O-Si-O bonding. In the second pathway, the nanoparticles were initially exposed to a 9:1 mixture of trimethyl silyl chloride and chlorodimethyl octenyl silane which was then followed by hydroboration of the double bonds, to afford hydroxyl groups with a spatially controlled density and surface-attachment via O-Si-C bonding. These functionalized surfaces were then activated with the titanium tetrachloride catalyst. In our approach, thus surface tethered catalyst provided the sites for n-hexyl isocyanate monomer insertion, to "build up" the surface-grown polymer layers from the "bottom-up". A final end-capping, to seal off the chain ends, was done via acetyl chloride. Compounds were characterized by FT-IR, 1H-NMR, GC-MS, GPC, and thermogravimetric analyses.

Melamine-Formaldehyde-Supported Titanium-Based Heterogeneous Ziegler-Natta Catalyst for Ethylene Polymerization in Slurry Process

Ethylene was polymerized at 40°C temperature and 1 atm. pressure using melamine-formaldehyde (M-F) supported titanium tetrachloride (TiCl4) catalyst. Polymer-supported catalysts were prepared with a different weight ratio of TiCl4/ M-F in hexane. The wt% titanium incorporated in the polymer matrix was determined by UV-visible spectroscopy. In addition, the resulting catalysts were characterized by SEM-EDX, XRD, and TGA. The catalytic productivity is found to be 4721.09 g PE/g Ti/h. The productivity of the catalysts also depends on the titanium content in the polymer matrix. The catalyst with titanium content 3.5 wt% showed maximum activity. These catalysts also showed good storability.

Broad Molecular Weight Polypropylene Synthesis using Mixed Internal Donor Incorporated Magnesium Dichloride Supported Titanium Catalyst

Magnesium dichloride supported titanium tetrachloride catalyst with mixed internal donor, comprised of ethylbenzoate and sulfolane, were synthesized. The composition characteristics of catalysts indicate incorporation of sulfolane to max 8.2 wt%, in addition to ethylbenzoate. The amount of incorporated donors in solid catalyst is dependent on the sulfolane concentration and reaction temperature of the process. A physical characteristics study of catalyst indicated that morphology, crystallite size, surface area, pore volume and titanium distribution have not been influenced much by incorporation of the second internal donor (sulfolane). The catalysts, in combination with triethyl aluminum as cocatalyst and p-ethoxyethylbenzoate as external donor, show good activity for propylene polymerization. The polypropylene synthesized with an optimized catalyst system shows broad molecular weight distribution as compared to ethylbenzoate based catalyst.

Synthesis of polypropylene with varied microstructure and molecular weights characteristics using supported titanium catalyst system

Propylene polymerizations were conducted in slurry phase batch process using different dialkyldimethoxysilanes as an external donor with magnesium dichloride (MgCl2) supported titanium tetrachloride (TiCl4) catalyst having diisobutylphthalate (DIBP) as an internal donor. The dialkyl group of the external donors like dimethyldimethoxysilane (DMDMS), diisopropyldimethoxysilane (DIPDMS) and dicyclopentyldimethoxysilane (DCPDMS) were found to influence on the microstructure and the molecular weight characteristics of synthesized polypropylene in addition to the initial rate of polymerization and decay index. DCPDMS gave highest productivity and high molecular weight polypropylene with improved kinetics while DMDMS gave lowest productivity in comparison. The molar equivalent combination of DCPDMS with DIPDMS and DMDMS respectively, resulted in producing polypropylene with tacticity pattern and molecular weight characteristics in between the individual alkoxysilane based system indicating the effect of alkyl group on the catalyst performance.

Isomerization of β-carotene by titanium tetrachloride catalyst

Isomerization of all-trans-β-carotene occurs during shaking with 0.5% of titanium tetrachloride catalyst in methylene chloride at room temperature. In the present study we compared two types of columns C18 and C30 and various solvent systems for the separation of β-carotene and its cis isomers by high performance liquid chromatography (HPLC). Results showed that β-carotene isomers were resolved by employing a C30 column with a mobile phase of methanol (100%) (A) and methylene chloride (100%) (B) under a gradient elution condition. A total of eleven cis isomers and one all-trans-β-carotene isomer were resolved within 50 min at a flow rate of 1 ml/min and detection wave-length of 470 nm.

Control of molecular weight distribution in propylene polymerization with Ziegler-Natta/metallocene catalyst mixtures

Propylene polymerization was investigated with a sequential addition of Ziegler-Natta and metallocene catalysts. From the fact that the molecular weights of polypropylene (PP) produced with Ziegler-Natta and with metallocene catalysts differ, it was possible to control the molecular weight distribution ( MWD ) of PP with a sequential addition of methylaluminoxane and rac-ethylenebis (indenyl) zirconium dichloride followed by triethylaluminum and magnesium dichloride-supported titanium tetrachloride catalyst. The obtained PP exhibited a wide MWD curve with shoulder peak. The position and height of each peak was controlled with the variation of polymerization time for each catalyst as well as the amount of each catalyst. The MWD of PP prepared with sequential addition of catalysts was much wider than that of PP obtained from each catalyst.

Olefin polymerization with titanium tetrachloride catalysts supported on surface‐modified silica

AbstractAfter modification of silica with benzoyl chloride (BC) to obtain BC‐modified SiO2 (BC‐SiO2), BC‐SiO2/TiCl4 and BC‐SiO2/BEM/TiCl4 catalysts were prepared by treating the BC‐SiO2 with TiCl4 directly or with butylethylmagnesium (BEM) followed by TiCl4, respectively. During the modification, BC reacts with hydroxyl groups of silica. In this way the corresponding ester is anchored on the silica surface and the CO group is coordinated with Ti and/or Mg. In addition, BEM is converted to MgCl2 in the reaction with TiCl4. These catalysts have reasonable activities for ethylene or propene polymerization.

Role of electron donor in propylene polymerization using magnesium chloride-supported titanium tetrachloride catalyst

The effect of bis-2-ethylhexyl phthalate (BEHP) and phenyl triethoxy silane (PES) as donors on the stereospecificity of propylene polymerization catalysis was investigated using a MgCl 2-supported TiCl 4 catalyst. It is suggested that BEHP plays an important role in the fixation of PES on the MgCl 2-supported TiCl 4 catalyst, and the fixed PES acts as an effective stereospecificity improver.

Polymerization of isoprene in n‐heptane with triethylaluminum–titanium tetrachloride catalyst. I. Effect of Al/Ti ratio on stereoregularity, conversion, molecular weight, and molecular weight distribution

AbstractThe influence of the Al/Ti ratio of the heterogeneous Ziegler–Natta catalyst system AlEt3–TiCl4 on the isoprene polymerization in n‐heptane at 30°C in a bench scale reactor was investigated. Each batch run consisted of 50 mL isoprene, 200 mL n‐heptane with 0.45 and 0.5g catalyst. Conversion of isoprene and molecular weights of polyisoprene increased with increasing Al/Ti ratio, reaching their maxima values at 1.0 and 1.2, respectively. Conversion and molecular weights decreased remarkably at a higher ratio of Al/Ti. As this ratio decreases from the value of 1.2 to 0.4, the cis1,4 content in polyisoprene decreased from 97 to 25%. When the ratio of Al/Ti increased from 1.2 to 2.2 the cis‐1,4 structure of polyisoprene decreased from 97 to 85%.

Effect of polymerization rate on the polyethylene structure obtained with a high activity catalyst system

The effect of polymerization rate on polyethylene structure, using magnesium reduced titanium tetrachloride catalysts together with the usual aluminium alkyl activator, is described. It is shown that the polymer bulk density and the nascent super-molecular structure formed during ethylene polymerization depends upon the rate of polymerization. The results indicate that, with increasing polymerization rate, the catalyst active sites produce polymer with different densities. One possible explanation for this phenomenon lies in considering the inhibition of crystallization by high polymerization rates. Experimental results on different polymer morphologies are discussed. Finally models for the structure of polymer particles are considered briefly.

Polymerization of propylene with γ‐Al2O3‐ or SiO2‐supported titanium tetrachloride catalyst

AbstractThe preparation of γ‐Al2O3‐ and SiO2‐supported titanium tetrachloride catalysts for the polymerization of propylene is described. The ESR spectra of these products, measured at −196°C, display broad signals with g‐values of 1,942 and 1,952 in the cases of γ‐Al2O3 and SiO2, respectively, which are assignable to Ti(III) species. The concentration of the Ti(III) species depends strongly upon the conditions of treatment. With these products as catalysts the polymerization of propylene takes place at 40 −75°C in the absence of any activator. The polymerization activity significantly depends upon the conditions of catalyst treatment, but it is approximately proportional to the concentration of the Ti(III) species. The molecular weight and the isotacticity of the resulting polymer remain almost unchanged. These results lead to the conclusion that Ti(III) is the active species in these catalysts.

Cyclocopolymerization of p‐chlorostyrene with 4‐vinylcyclohexene

Abstract4‐Vinylcyclohexene was polymerized by triethyl‐aluminum–titanium tetrachloride catalyst (mole ratio 5.4:1). Copolymerization of 4‐vinylcyclohexene with p‐chlorostyrene by the same catalyst was also carried out. For these polymerization results, the Roovers‐Smets equation was applied and the reactivity ratio parameters, Kc, Kc′, r2 and r3 were determined as follows: Kc = Kc/k11 = 9.1; Kc′ = kc/k12 ∼ ∞; r2 = k22/k21 = 1.45; r3 = k31/k32 ∼ 0, where subscripts 1, 2 and 3 indicate 4‐vinylcyclohexene, p‐chlorostyrene, and cyclized polymer anion, respectively.

Polymerization of 2,2,2‐trifluoroethyl vinyl ether

AbstractThe polymerization of 2,2,2‐trifluoroethyl vinyl ether by six different catalyst systems was examined. Low‐temperature studies (−78°C) with boron trifluoride etherate catalyst in hydrocarbon and chlorinated solvents slowly yielded low molecular weight polymers which were amorphous and noncrystallizable upon cold drawing. Under similar conditions, polymerizations with boron trifluoride gas were spontaneous, quantitative, and gave relatively high molecular weight, form‐stable, amorphous polymer. Heterogeneous polymerizations with chromium trioxide crystals in toluene at 68°C and bulk reactions with ethylmagnesium bromide–carbon tetrachloride catalyst at 40°C failed to produce polymer. Room temperature runs with triisobutylaluminum–titanium tetrachloride catalyst gave amorphous, tacky material. Aluminum hexahydrosulfate heptahydrate (AHS) initiated polymerizations conducted at 25 and 60°C gave low yields of mixtures of amorphous and crystalline polymers, the ratio depending upon the polymerization solvent employed. The infrared spectra and x‐ray diffraction intensity curves of crystalline and amorphous poly(trifluoroethyl vinyl ether) are reported and compared herein for the first time.

Synthesis of crystalline polyvinylcyclobutane and polyvinylcycloheptane

AbstractThe synthesis of vinylcyclobutane and vinylcycloheptane is described. These compounds were polymerized to crystalline polyvinylcyclobutane and polyvinylcycloheptane with a triisobutyl aluminum–titanium tetrachloride catalyst system.

Study on Titanium Tetrachloride Catalysts for Fries Reaction.

Reactivity of phenol esters in the Fries reaction has been investigated by using titanium tetrachloride as a catalyst in the preceding experiment. This report deals with the Fries reaction of cresyl acetate and the yield of acetophenone, its reacting condition, time and temp., the amount of catalyst and solvent, etc. have been investigated. Syntheses of additive products of m- and p-acetates and titanium tetrachloride were carried out at first, their decomposition temp. and the synthesis of acetophenone from the additives have been investigated. m-Cresyl acetates yielded o- and p-compounds, while p-cresyl acetate yielded o-compound only. In each case, the max. yield was 90% and 70%, respectively, at the decomposition temp. of additive products. The change of reaction time in these temp, ranges showed great effect in its yield. In case of m-cresyl acetate, the yield of p-compound became higher when aluminium chloride was used as a catalyst.

Separated aluminum alkyl–titanium tetrachloride catalysts for isoprene polymerization

AbstractThe liquid portions of triisobutyl–aluminum TiCl4 catalysts were partially or completely removed from catalysts formed at Al/Ti ratios of 0.5, 0.6, 1.0, 1.2, 2.0, 3.0, and higher. The partially separated catalysts (0.5–1.2 Al/Ti) are still highly active for the polymerization of isoprene to a high cis polymer. The completely separated solid is inactive, but regains polymerization activity if triisobutyl aluminum or diisobutyl‐aluminum chloride is added back. Polymer yield quickly reaches a maximum and then falls off sharply on addback of more trialkyl; the drop in yield is much slower on addback of excess dialkyl halide. The results indicate that trialkyl or dialkyl halide plus β‐TiCl3 make active catalyst systems for cis‐polyisoprene; the alkyl dihalide is not satisfactory. Excess trialkyl changes the solid surface or mechanism and results in lowered solid polymer yield and increased oily oligomer formation. Completely separated high ratio (2.0 and 3.0 Al/Ti) catalysts are more active than those only partially separated but still much less active than catalysts formed at lower ratios. Addbacks of either aluminum trialkyl or dialkyl halide depress the solid cis polymer yield. Without any separation no solid polymer at all forms. The results suggest that the catalyst at these high ratios is a solid complex of β‐TiCl3 with an organometallic. A simple coordination mechanism is sufficient to correlate all the experimental results.

Polymerization of styrene with n‐butyllithium–titanium tetrachloride catalysts

AbstractThe polymerization of styrene by n‐butyllithium and titanium tetrachloride has been examined. Isotactic polystyrene is obtained only when 3.00 > n‐BuLi/TiCl4 > 1.75. At ratios less than 1.75 and greater than 3.00 only amorphous polystyrene (soluble in MEK) was formed. The molecular weights of the amorphous fraction were determined, and it was interesting to note that the amorphous polymer shows strong fluorescence under ultraviolet light. Concomitantly with the formation of isotactic polystyrene, trans‐stilbene was also formed.

Polymerization of butadiene with aluminum triisobutyl–titanium tetrachloride catalyst system

AbstractThe effect of Al/Ti molar ratio, temperature, and solvent on the microstructure of polybutadiene prepared with an aluminum triisobutyl–titanium tetrachloride catalyst system was investigated. Although polymers containing as much as 98% trans‐1,4 structure were obtained, under appropriate conditions, no polymers with greater than 60% cis‐1,4 structure were obtained. The amount of 1,2‐structure was generally below 10%. The rate of polymerization was measured at 25°C. in heptane by following the drop of butadiene pressure with time in a constant volume apparatus. The rate was a function of the Al/Ti molar ratio and was directly proportional to the amount of catalyst used. The rate of polymerization was proportional to the square of monomer pressure at Al/Ti ratios greater than 2.0. When the molar ratio was between 1.0 and 1.6, the rate was proportional to the first power of the monomer pressure. At molar ratios of 1.8 and 1.9 the dependence of rate on monomer pressure could be represented by −dP/dt = aP + bP2, indicating the possible existence of two concurrent reactions. When the ratio fell below unity the uptake of butadiene was at first rapid but soon slowed to a stop. Possible kinetic schemes are discussed in terms of Rideal and Langmuir‐Hinshelwood mechanisms.