Polymerization of propylene by the three-component system comprising titanium(III) chloride,ethylaluminum sesquichloride,and sodium sulfate

Sodium sulfate increases the polymerization activity of the titanium(III) chloride (AA)–ethylaluminum sesquichloride system for the polymerization of propylene. The reaction of ethylaluminum sesquichloride with sodium sulfate at mild conditions isolates diethylaluminum chloride, which is responsible for the polymerization activity. The reaction of these components at severe conditions forms an organometallic compound containing sulfate, (C₂H₅)₄Al₂SO₄, and this compound is a powerful activator for titanium(III) chloride.     

Synthesis, characterization and catalytic activity of the complex titanium bis(dimethylmalonate)-bis(diethylamido) in the polymerization of propylene

In this account we present the synthesis, characterization and catalytic activity in the polymerization of propylene of a bis(dimethyl malonate) titanium bis(diethylamine) complex (1). The complex exhibits in solution a dynamical isomerization following an internal Bailar twist. The activation of complex 1 was obtained by its reaction with methylalumoxane (MAO). The activated complex in solution shows a different dynamic process involving an equilibrium between a monodentate η¹ and bidentate η² binding of the dimethylmalonate ligand to the metal center. This equilibrium is responsible for the formation of, at least, two active species for the polymerization reaction bearing major symmetry differences. The monodentate coordination (opened form) of the ligand was found to be the major form of the active species of the complex when activated with MAO, most probably due to a strong interaction of the oxygen atoms in the ligand with the strong Lewis acid co-catalyst. The active species in the polymerization were studied by NMR and ESR spectroscopies. The resulting polypropylene showed elastomeric properties with low tacticites.     

Polymerization mechanism of vinyl chloride with titanium tetrabutoxide–ethylaluminum sesquichloride catalyst and some physical properties of poly(vinyl chloride) prepared at low temperature

The mechanism of vinyl chloride polymerization by titanium tetrabutoxide–ethylaluminum sesquichloride catalyst system was investigated from the view of the stereoregularity of poly(vinyl chloride). The samples were prepared at a selected temperature in the range from 23 to ?78°C. The tactic triads, obtained from 220-MHz NMR spectra, show clearly the adequacy of Bernoullian statistics in describing the mechanism for stereochemical propagation. The chain propagation proceeds according to Bernoullian statistics with syndiotactic placements favored by 550 cal/mole. These results suggest that vinyl chloride polymerizes by a free-radical mechanism under the action of the present catalyst system.     

Crystal and molecular structures of the binuclear complex of rhodium(III) chloride with selenium dichloride and the complex of iridium(III) chloride with sulfur dichloride and tetrachloride

Institute of General and Inorganic Chemistry, Ukrainian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 33, No. 3, pp. 146–148, May–June, 1992.     

New dinuclear fluorine-containing bis(salicylidene)imine titanium complex: synthesis and catalytic properties in polymerization of ethylene and propylene

New dinuclear titanium(IV) dichloride complex with the chelating bis-4,4-bis-imine-(3,5-di-tert-butylsalicylidene)octafluorobiphenyl ligand was synthesized. In the presence of polymethylaluminoxane (MAO), the complex showed high catalytic activity in ethylene polymerization leading to high molecular (M _n 2500000) linear polyethylene with a high polydispersity index (M _w/M _n 7.0) and high melting point (142 °C). The catalytic activity in propylene polymerization in a medium of liquid monomer is substantially lower, and the polypropylene formed is a high molecular atactic elastomer.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2652–2656, December, 2004.     

Cyclotrimerization of acetylene by the tris(acetylacetonato)titanium(III)–diethylaluminum chloride system

Reaction of acetylene with tris(acetylacetonato)titanium(III) and diethylaluminum chloride system leads to formation of benzene, a trace of ethylbenzene, and a small amount of polyacetylene. The isotopic composition of products obtained from cyclotrimerization of acetylene-d₂ and an equimolar mixture of acetylene and acetylene-d₂ is investigated to elucidate the mechanism of the cyclotrimerization. The results suggest a mechanism in which an acetylene inserts into the metal—ethyl bond formed by reaction of Ti(acac)₃ and Al(C₂H₅)₂Cl, followed by insertion of two acetylene molecules and elimination of a hydrogen atom from the first inserted acetylene to yield an ethylbenzene and a metal hydride intermediate. The metal hydride intermediate catalyzes acetylene cyclotrimerization to give benzene. During the reaction, the hydrogen atom in the metal hydride intermediate does not exchange with the hydrogen atom in the inserted acetylene molecules.     

Stability of the anatase phase in nanodimensional titanium dioxide doped with europium(III), samarium(III), and iron(III)

lid solutions Ti_1−x M _x O_2−x/2 in the anatase and rutile forms were obtained from the precursors Ti_1−x M _x (OCH₂CH₂O)_2−x/2 at T = 450–900 °C. The temperature and concentration dependence of the phase transformation of anatase to rutile in Ti_1−x M _x O_2−x/2 was investigated by Raman spectroscopy. It was shown that the anatase phase is stabilized most effectively by the Eu³⁺ dopant.     

The initiation of polymerization by organometallic compounds—IV. Initiator efficiency in polymerization of acrylonitrile by tetrakis(dimethylamido)titanium(JV)

A titrimetric method has been developed for following the removal of titanium-dimethylamine bonds during the polymerization of acrylonitrile by tetrakis(dimethylamido)titanium(IV) (T₄). The kinetics of the reaction of T₄ with monomer can be interpreted in terms of a sequence of insertion reactions in which dimethylamino ligands are successively removed from titanium. The calibration of a GPC instrument for measurement of the molecular weights of polyacrylonitrile is discussed. The results of initiator consumption and polymer molecular weight measurements are combined to allow the efficiency of initiation by T₄ to be assessed. Over the whole conversion range, titanium-dimethylamine bonds are broken in about 50 per cent excess over those used for polymerization. However, at high conversions more than one polymer chain is produced per titanium atom reacted.     

Anionic polymerization of methyl methacrylate using tetrakis[tris(dimethylamino)phosphoranylidenamino] phosphonium (P5+) as counterion in tetrahydrofuran

A novel metal‐free initiator, i.e. the salt of the tetrakis[tris(dimethylamino)phosphoranylidenamino]phosphonium (P₅⁺) cation with the 1,1‐diphenylhexyl (DPH^–) anion was prepared by cation metathesis. It initiates a very fast and controlled anionic polymerization of methyl methacrylate in THF. Kinetic investigations between –20 and +20°C using a flow tube reactor provide nearly linear first‐order time‐conversion plots with half‐lives below 0.1 s, a linear dependence of the number‐average degree of polymerization, and rather narrow molecular weight distributions (M_w/M_n ≈ 1.2). ¹³C NMR measurements on a model of the active chain end (the P₅⁺ salt of ethyl isobutyrate) in THF‐d₈ show 15 and 25 ppm upfield shifts of the α‐carbon compared to the dimers and tetramers of the lithium ester enolate, respectively, indicating a non‐aggregated structure and an increased charge density on the α‐carbon.     

The initiation of polymerization by organometallic compounds—V. The termination mechanism in the polymerization of acrylonitrile initiated by tetrakis(dimethylamido)titanium(IV)

A simple method is described for the preparation of pure, dry alcohols, tritiated in the hydroxyl group. The polymerization of acrylonitrile initiated by tetrakis(dimethylamido)titanium(IV) has been terminated by quenching with tritiated isopropanol at varying reaction times, and the radioactivity of the polymer has been determined, in order to measure the concentration of metal-polymer bonds present in the reaction. The results indicate that about 97 per cent of the polymer present has been terminated by a reaction leading to detachment of the polymer chain from the metal centre. A very small fraction of the total polymer is terminated by a reaction which does not lead to detachment of the polymer. Possible reaction mechanisms are discussed.     

Lanthanocene amide complexes as single‐component initiators for the polymerization of (dimethylamino)ethyl methacrylate

Polymerization of (dimethylamino)ethyl methacrylate (DMAEMA) by lanthanocene amide complexes was investigated. The results show that (MeC₅H₄)₂LnN(i‐Pr)₂[tetrahydrofuran (THF)] (Ln = Y, Er, Yb), (MeC₅H₄)₂YbNC₅H₁₀(HNC₅H₁₀) (HNC₅H₁₀ = piperidine), (MeC₅H₄)₂YbNPh₂(THF), and (t‐BuC₅H₄)₂YbNPh₂(THF) are effective initiators for the polymerization of DMAEMA, and the molecular weights of the polymers obtained exceed 100 × 10³. The polymerization reactions can be varied over quite a broad range of temperatures from ?78 to 40 °C. The central metals and amido groups had a significant effect on the polymerization activity. The increasing activity of central metals and amido groups was Yb < Er < Y and NPh₂ < N(i‐Pr)₂ < NC₅H₁₀, respectively. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 612–616, 2002; DOI 10.1002/pola.10141     

Reduction of ammonium nitrate with titanium(III) chloride in acid media

Investigation of acid ammonium nitrate solutions in the presence of titanous chloride has led to a new mechanism of nitrate reduction. It is proposed that the reduction proceeds through two electron changes and terminates as nitrous oxide in solutions whose acid content is greater than 0.1 N. The stronger reducing power of the titanous buffer method previously reported arising from a direct pH affect on the titanous -titanyl couple has been discerned rather as an effect arising from different reduction products in that media. The affects of prolonged reaction at 100° and use of osmium tetroxide catalyst were examined. A pH of 4.5 and 100% excess of titanous was insufficient to reduce nitrate to ammonia quantitatively.     

Homo-and copolymerization of propylene and ethylene in the presence of titanium dichloride complexes with dioxolane dicarboxylate and bis(difurylmethanephenoxyimine) ligands

The polymerization of propylene and ethylene and the copolymerization of these olefins with postmetallocene catalysts [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol] titanium(IV) dichloride and bis{N-(3,5-ditert-butylsalicylidene)-4-[bis(5-methyl-2-furyl)methyl]aniline}titanium( IV) dichloride have been studied. The polymerization of propylene and its copolymerization with ethylene have been carried out in a liquid monomer, while the polymerization of ethylene has been performed in toluene at the constant concentration of the monomer. Polymethylaluminoxane has been used as a cocatalyst. The activity of the catalysts in the polymerization of propylene and ethylene at 50°C is ～ 10 and ～45 kg PP/mol Ti h mol C₃H₆/l and 178.5 and 2700 kg PE/mol Ti h mol C₂H₄/l, respectively. It has been established that, in the copolymerization of propylene with ethylene, the active sites of both catalysts selectively polymerize ethylene. The resulting copolymers have a block structure (r ₁ r ₂= 4.6); as a result, the crystalline phase of polyethylene is formed in them. Polypropylene and propylene-ethylene copolymers are elastomeric materials. Polypropylene samples synthesized with [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]titanium(IV) dichloride demonstrate a high melting point (150–157°C) in combination with good elastic properties. Polyethylene is a linear polymer with the degree of crystallinity varying from 37 to 45% and a melting point of 133–134°C. The mechanical properties of the polymers and copolymers have been investigated.     

Features of the oxidative polymerization of aminothiazole in the presence of iron(III) chloride

A new conjugated polymer with semiconducting characteristics-polyaminothiazole-was obtained by oxidative polymerization of 2-aminothiazole in the presence of iron(III) chloride. A reaction scheme is proposed on the basis of the data from IR, ESR, and electronic spectroscopy. It involves the formation of an intermediate aminothiazole-FeCl₃ complex with coordination of the initiator at the nitrogen atom and subsequent oxidation of another molecule of aminothiazole by this complex with the formation of a radical-cation, leading to polymerization. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 91–95, March–April, 2007.     

Design of postmetallocene catalytic systems of arylimine type for olefin polymerization: XIV. Synthesis of (N-Allyloxyaryl)salicylaldimine ligands and their complexes with titanium(IV) dichloride

By reaction of salicylaldehydes with bulky substituents in the positions 3 and 5 with o-, m-, and p-allyloxyaniline hydrochlorides in the presence of triethylamine a series of the corresponding (N-aryl)-salicylaldimines was obtained, which with TiCl₂(OPr-i)₂ afforded complexes of titanium(IV) dichloride L₂TiCl₂.     

Salt effect in the base-catalyzed polymerization of unsaturated amide compounds. III. Nature of the polymerization system

Coordination complexes of lithium chloride with polar solvents and monomers were isolated, and their physical properties were studied. The parallel between stabilities of isolated complexes and coordination function in the polymerization system is discussed. The increase of the Q and e values of p-vinylbenzamide (VBA) supports the mechanism of vinyl-type polymerization of VBA in the presence of the salt. The specific solvent effect of dimethyl sulfoxide was determined by measurement of electrical conductivity of a model system.     

Homopolymerization of ethylene and copolymerization with 1-butene in the presence of bis(cyclopentadienyl)titanium dichloride and diisobutylaluminum chloride

Ethylene was homopolymerized and copolymerized with 1-butene in benzene at 30°C. with the use of bis(cyclopentadienyl)titanium dichloride and diisobutylaluminum chloride as catalyst. Both freshly prepared catalyst and catalyst which had been aged up to 114 hr. were used. When the catalyst was aged prior to adding the monomer, the yields were lower and the products had higher molecular weights. In the case of copolymers, aging of the catalyst also affected the relative concentrations of the comonomers in the products. 1-Butene was an effective chain transfer agent under all reaction conditions. The data were found to be consistent with the previously suggested mechanism according to which different species initiate polymerizations with freshly mixed and aged catalysts.