Influence of SeOCl2 on the polymerization of propylene by TiCl3–Al(C2H5)3

The influence of SeOCl₂ on the polymerization of propylene by TiCl₃–Al(C₂H₅)₃, and the temperature dependence of the stereospecificity of the catalyst, TiCl₃–Al(C₂H₅)₃, have been investigated. SeOCl₂ decreases the rate of polymerization and increase the stereospecificity of the catalyst, which could be explained on the basis of a decrease of the concentration of Al(C₂H₅)₃ accompanied by a reaction between Al(C₂H₅)₃ and SeOCl₂. On the other hand, the stereospecificity of the catalyst, TiCl₃–Al(C₂H₅)₃, increases gradually with a decrease in polymerization temperature from 40 to 0°C. From these results, we conclude that SeOCl₂ exerts no essential influence on the polymerization of propylene by TiCl₃–Al(C₂H₅)₃, and that the stereospecificity of the catalyst is attributed mainly to the reducing ability of the organometallic compound.     

Kinetic studies of polymerization of propylene with active TiCl3–Zn(C2H5)2

In order to elucidate the structure of the Ziegler-Natta polymerization center, we have carried out some kinetic studies on the polymerization of propylene with active TiCl₃—Zn(C₂H₅)₂ in the temperature range of 25–56°C. and the Zn(C₂H₅)₂ concentration range of 4 × 10^?3–8 × 10^?2 mole/1., and compared the results with those obtained with active TiCl₃—Al(C₂H₅)₃. The following differences were found: (1) the activation energy of the stationary rate of polymerization is 6.5 kcal/mole with Zn(C₂H₅)₂ and 13.8 kcal./mole with Al(C₂H₅)₃; (2) the growth rate of the polymer chains with Zn(C₂H₅)₂ is about times slower at 43.5°C.; and (3) the polymerization centers formed with Zn(C₂H₅)₂ are more unstable. It can be concluded that the structure of the polymerization center with Zn(C₂H₅)₂ is different from that with Al(C₂H₅)₃.     

Polymerization of styrene with ZrCl4 and ZrCl3 in combination with Al(C2H5)3

The polymerization of styrene with two catalyst systems consisting of Al(C₂H₅)₃ in combination with ZrCl₄ or ZrCl₃ has been studied. The rate of polymerization with catalyst concentration was first-order with ZrCl₄ system and second-order with ZrCl₃ system, but at higher catalyst concentrations in both cases, the rate progressively decreases and finally attains a low value. The rate of polymerization is, however, proportional to the square of the monomer concentration in both the cases. The overall energy of activation was 10.9 kcal./mole and 6.45 kcal./mole in these systems. The polymers obtained with ZrCl₄ were of lower molecular weights as compared to those obtained with ZrCl₃. The polymers in both the cases had amorphous character.     

Monomer-isomerization polymerization. VI. Isomerizations of butene-2 with TiCl3 or Al(C2H5)3–TiCl3 catalyst

A study of the isomerization of butene-2 with TiCl₃ or Al(C₂H₅)₃–TiCl₃ catalyst in n-heptane has been investigated at 60–80°C to elucidate further the mechanism of monomer-isomerization polymerization. It was found that positional and geometrical isomerizations in the presence of these catalysts occurred concurrently with activation energies of 14–16 kcal/mole. The presence of Al(C₂H₅)₃ with TiCl₃ catalyst could accelerate the initial rates of these isomerizations and initiate the monomer-isomerization polymerization of butene-2. From the results obtained, it was concluded that the isomerization of butene-2 proceeds via an intermediate σ-complex between the transition metal hydride and butene isomers.     

Study of Hydrocarbon-Soluble Organometallic Catalysts. III. Investigations on the Activity and Electric Conductivity of Al(C2H5)3—M(C5H7O2)n Catalysts Employed in the Synthesis of Stereoregular Polyacetylene

The aim of the present work is to establish some correlations between the catalytic activity of several organometallic hydrocarbon-soluble complex systems and the electric conductivity, as a method which expresses the ionization degree of these catalyst types. The following systems were studied: Al(C₂H₅)₃—VO(C₅H₇O₂)₂; Al(C₂H₅)₃—Cr(C₅H₇O₂)₃, Al(C₂H₅)₃—Co(C₅H₇O₂)₃. The catalytic activity was determined at various molar ratios of AlEt₃/M(C₅H₇O₂)_n in the stereoregular polymerization reaction of acetylene, where M is a metal. The visible and ultraviolet absorption spectra of the catalysts, as well as the variation of extinctions at various AlEt₃/M(C₅H₇O₂)_n molar ratios were also determined. The systems with an optimal catalytic activity also show maximum values of electric conductivity and extinctions. The composition, degree of ionization of the catalyst, and the way in which this influences the catalytic activity are also discussed.     

Modification mechanism in olefin polymerization catalysts TiCl4/MgCl2–aromatic ester–Al(C2H5)3

An IR/UV study of the interaction between ethyl benzoate and Al(C₂H₅)₃ in dilute heptane solution at 25–75°C demonstrated that the ester is readily reduced under these conditions with the formation of two aluminum dialkyl alkoxides, Al(C₂H₅)₂ and Al(C₂H₅)₂OC(C₂H₅)₂C₆H₅, as major products. Rate constants of the reduction of the initial AI(C₂H₅)₃ · ester complex by free AI(C₂H₅)₃ are 2.9 (26°C), 14.4 (50°C), and 59.6 (75°C) L/mol min; E_act = 52.0 kj/mol. Study of propylene polymerization with this catalytic system at 50°C showed that preliminary aging of the AI(C₂H₅)₄–ethyl benzoate mixtures at 25°C for 24 h and at 50°C for 2 h does not adversely affect catalyst performance. These data suggest that the possible actual modifier in this catalytic system is aluminum alkoxide with a highly branched tertiary alkoxy group.     

Monomer-isomerization polymerization. V. Effects of transition metal compounds on monomer-isomerization polymerizations of butene-2 and pentene-2

In order to clarify the correlation between polymerization and monomer isomerization in the monomer-isomerization polymerization of β-olefins, the effects of some transition metal compounds which have been known to catalyze olefin isomerizations on the polymerizations of butene-2 and pentene-2 with Al(C₂H₅)₃–TiCl₃ or Al(C₂H₅)₃–VCl₃ catalyst have been investigated. It was found that some transition metal compounds such as acetylacetonates of Fe(III), Co(II), and Cr(III) or nickel dimethylglyoxime remarkably accelerate these polymerizations with Al(C₂H₅)₃–TiCl₃ catalyst at 80°C. All the polymers from butene-2 were high molecular weight polybutene-1. With Al(C₂H₅)₃–VCl₃ catalyst, which polymerizes α-olefins but does not catalyze polymerization of β-olefins, no monomer-isomerization polymerizations of butene-2 and pentene-2 were observed. When Fe(III) acetylacetonate was added to this catalyst system, however, polymerization occurred. These results strongly indicate that two independent active centers for the olefin isomerization and the polymerizations of α-olefins were necessary for the monomer-isomerization polymerizations of β-olefins.     

Photochemical reactions of (CO)2 (PPh3)MnC5H4Fe(CO)2C5H5 and (CO)2(PPh3)MnC5H4COFe(CO)2C5H5 with PPh3

Conclusions The photochemical reactions of (CO)₂(PPh₃)MnC₅H₄Fe(CO)₂C₅H₅ and (CO)₂(PPh₃)MnC₅H₄COFe(CO)₂C₅H₅ with PPh₃ gave the products of replacing the CO on the Fe atom by PPh₃: respectively (CO)₂(PPh₃)MnC₅H₄Fe (CO)(PPh₃)C₅H₅ and (CO)₂(PPh₃)MnC₅H₄COFe(CO)(PPh₃)C₅H₅.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2813–2815, December, 1977.     

Kinetics of Polymerization of 1,3-Dioxolan Initiated by C6H5COSbF,and (C6H5)3C+SbF8 Salts

Polymerizations of 1,3-dioxolan initiated by oxycarbenium salt CeHsCO⁺SbFe^? and triphenylmethylium salt (C6H₅)₃C⁺SbF₆ ^? proceed with induction periods. C₆H₅CO⁺SbF6 initiates polymerization by a direct addition, while initiation with (C₆H₅CO⁺SbFe^?proceeds through the intermediately formed 1,3-dioxolan-2-ylium salt. Kinetic analysis of polymerization of 1,3-dioxolan, initiated by oxycarbenium salt or triphenylmethylium salt revealed that, in spite of different chemisty of initiation, both processes proceed with a slow initiation on monomer and fast initiation on polymer. The pertinent kinetic equations were derived and it was found, that the rate constant of propagation (k) does not depend on the structure of initiator used, being equal to 25 ± 5 liter/mole-sec (0°C, CH₂Cl₂ or CH₃NO₂).     

Kinetics and mechanism of polymerization yielding stereoblock poly(methyl methacrylate) with VCl4-Al(C2H5)3 catalyst system

Methyl methacrylate was polymerized at 40°C with the VCl₄–AlEt₃ catalyst system in n-hexane. The rate of polymerization was proportional to the catalyst and monomer concentration at Al/V ratio of 2, indicating a coordinate anionic mechanism of polymerization. NMR spectra were further used to confirm the mechanism of polymerization and stability of active sites responsible for isotacticity.     

Polymerization of 2,5-dimethyl-3,4-dihydro-2H-pyran-2-carboxyaldehyde (methacrolein dimer). Part II

2,5-Dimethyl-3,4-dihydro-2H-pyran-2-carboxyaldehyde (methacrolein dimer) gave a polymer consisting of only recurring bicyclic structure of 1,4-dimethyl-6,8-dioxa-bicyclo-[3,2,1] octane with the use of Lewis acid and protonic acid as catalyst at room temperature. On the other hand, the polymer obtained by using BF₃·(C₂H₅)₂O under ?78°C. was found to have the structures produced by the aldehyde group polymerization as well as the bicyclic ones. The polymer obtained at ?40°C. had a low decomposition temperature (164°C.) owing to the presence of polyacetal group, whereas the fully saturated bicyclic polymer had a considerably high one (346°C.). The main factors affecting the polymerization were polymerization temperature and catalyst. Lowering temperature increased the polymerization of the aldehyde group. Anionic catalysts and weak cationic catalyst such as Al(C₂H₅)₃? H₂O, which were active catalysts for acrolein dimer, did not initiate the polymerization of methacrolein dimer. The fact that the relative viscosity of the polymer increased with polymerization time shows the polymerization of this monomer is a successive reaction.     

Investigations on the kinetics of copolymerization of vinyl acetate with acrylonitrile by Co(acac)3–Al(C2H5)3 catalyst system

Vinyl acetate and acrylonitrile were copolymerized with Co(acac)₃-Al(C₂H₅)₃ catalyst system in benzene at 40°C. The rate of copolymerization is linearly proportional to monomer concentration and catalyst concentrations up to a certain value. The overall activation energy was found to be 11.3 kcal/mole. The effect of hydroquinone on the rate of copolymerization indicates the presence of free radicals in this system. The possibility of simultaneous formation of coordinate anionic and free radical active sites has been proposed.     

Rates of polymer formation and monomer consumption in the solution polymerization of trioxane catalyzed by BF3 · O(C2H5)2

In the solution polymerization of trioxane catalyzed by BF₃ · O(C₂H₅)₂ at 30°C. the amount of the methanol-insoluble polyoxymethylene is less than the amount of monomer consumed. This difference was much larger than the amount of formaldehyde determined in the polymerized system and could not also be explained in terms of the amount of the methanol-soluble oligomer. Tetraoxane was detected in large quantities by gas chromatography in the polymerized solution of trioxane. Therefore, the difference between the amounts of the methanol-insoluble polymer and the monomer consumed was ascribed partly to the formation of tetraoxane. In spite of the fact that tetraoxane was polymerized more easily than trioxane by BF₃ · O(C₂H₅)₂, an almost constant amount of tetraoxane was produced, independent of the kind of solvent and the polymer yield. This suggests the existence of an equilibrium concentration of tetraoxane. On the other hand, the formation of trioxane was observed in the solution polymerization of tetraoxane by BF₃ · O(C₂H₅)₂. This suggests that the formation of tetraoxane during the trioxane polymerization is due to a back-biting reaction in which the growing chain end of trioxane attacks the oxygen atom in its own chain with depolymerization of tetraoxane.     

Mechanism of Polymerization of 1, 3-Dioxolane Initiated by (C2H5)3 O+SbCl6 and SbCl5

The kinetics of polymerization of 1, 3-dioxolane (DiOX) initiated by (C₂H₅)₃O⁺SbCl₆ and SbCl₅ has been studied and the elementary stages of the process have been considered. The polymerization of DiOX by (C₂H₅)₃O⁺SbCl₆-is shown to proceed at a steady rate to high conversion. A constant concentration of active centers in the system is maintained due to the equal rates of decomposition of active centers and disproportionation. The nonsteady-state character of DiOX polymerization initiated by SbCl₅is associated with a relatively lower stability of the counter-ion SbCl₅ OR^? compared with SbCl₆. The initiation of DiOX polymerization by (C₂H₅)₃O⁺SbCl₆ proceeds without hydride-transfer reactions, and the concentration of active centers in the system is determined not by processes taking place in the initiation stage, but by the existence of a definite kind of equilibrium with the participation of active centers.     

Some data on the character of the titanium -cyclopentadienyl ring bond in C5H5Ti(OC2H5)3 and (C5H5)2 Ti(OCOCH3)2

Summary On the basis of the formation of ferrocene during the reaction of C₅H₅Ti(OC₂H₅)₃ and (C₅H₅)₂Ti(OCOCH₃)₂ with FeCl₂ and the ease with which the bond of the cyclopentadienyl ring with the metal in these compounds may be hydrolyzed the hypothesis has been stated that the bond of the titanium atom with the cyclopentadienyl rings in (C₅H₅)₂Ti(OCOCH_{5 2} and C₅H₅Ti(OC₂H₅)₃ has an ionic character to a considerable degree.     

(C5H6N4O)(C5H5N4O)3(C5H4N4O)[Bi2Cl11]Cl2 as a simple and efficient catalyst in Biginelli reaction

A highly efficient and facile procedure for the one‐pot three‐component synthesis of 3,4‐dihydropyrimidin‐2‐(1H )ones/thiones from the one‐pot condensation of aldehyde, β‐dicarbonyl compound and urea/thiourea was developed. The methodology is applicable to a wide range of substrates with high yield in the presence of (C₅H₆N₄O)(C₅H₅N₄O)₃(C₅H₄N₄O)[Bi₂Cl₁₁]Cl₂. The complex is an air‐stable, environmentally friendly and recoverable catalyst and can efficiently catalyze the Biginelli reaction. The catalyst has high catalytic efficiency with low catalyst loading, and can be recycled ten times with only a small loss of activity.     

Cationic polymerization of α,β-disubstituted olefins. IV. Stereospecific polymerization of propenyl alkyl ethers catalyzed by BF3·O(C2H5)2 and Al2(SO4)3–H2SO4 complex

The cis- and trans-propenyl alkyl ethers were polymerized by a homogeneous catalyst [BF₃·O(C₂H₅)₂] and a heterogeneous catalyst [Al₂(SO₄)₃–H₂SO₄ complex]. Methyl, ethyl, isopropyl, n-butyl and tert-butyl propenyl ethers were used as monomers. The steric structure of the polymers formed depended on the geometric structures of monomer and the polymerization conditions. In polymerizations with BF₃·O(C₂H₅)₂ at ?78°C., trans isomers produced crystalline polymers, but cis isomers formed amorphous ones except for tert-butyl propenyl ether. On the other hand, highly crystalline polymers were formed from cis isomers, but not from the trans isomers in the polymerization by Al₂(SO₄)₃–H₂SO₄ complex at 0°C. The x-ray diffraction patterns of the crystalline polymers obtained from the trans isomers were different from those produced from the cis isomers, except for poly(methyl propenyl ether). The reaction mechanism was discussed briefly on these basis of these results.     

Monomer-isomerization polymerization. XXIII.. Monomer-isomerization polymerization of 5-phenyl-2-pentene with ziegler–natta catalysts

5-Phenyl-2-pentene (5Ph2P) was found to undergo monomer-isomerization polymerization with TiCl₃–R₃Al (R = C₂H₅ or i-C₄H₉, Al/Ti > 2) catalysts to give a polymer consisting of exclusively 5-phenyl-1-pentene (5Ph1P) unit. The geometric and positional isomerizations of 5Ph2P to its terminal and other internal isomers were observed to occur during polymerization. The catalyst activity of alkylaluminum examined to TiCl₃ was in the following order: (C₂H₅)₃Al > (i-C₄H₉)₃Al > (C₂H₅)₂AlCl. The rate of monomer-isomerization polymerization of 5Ph2P with TiCl₃–(C₂H₅)₃Al catalyst was influenced by both the Al/Ti molar ratio and the addition of nickel acetylacetonate [Ni(acac)₂], and the maximum rate was observed at Al/Ti = 2.0 and Ni/Ti = 0.4 in molar ratios.     

Study of (π-C5H5)2Ti(C2H5)Cl and its higher homologs in soluble Ziegler catalysts

Soluble ethylene polymerization catalysts derived from (π-C₅H₅)₂Ti(R)Cl and R′AlCl₂ where R is ethyl or higher alkyl and R′ may be methyl or ethyl, were studied both by polymerization kinetics at 0°C and by diagnostic experiments. An early acceleration in rate occurred at this temperature in toluene solvent which was due to a solvent dependent increase in catalyst activity, not to a gradual formation of catalyst. No such solvent effect was found in nonaromatic solvents. The subsequent decay in rate, at least at low temperatures, did not depend upon valence reduction. The effect of Al/Ti ratio was studied, and certain discrepancies in the literature were shown to be due to the method of making kinetic measurements. Oxygen, which has previously been reported to affect the polymerization rate with these catalysts, was also found to eliminate the acceleration period in toluene when present in the amount of 1% of the catalyst. These catalysts gave polymers at low temperature for which the active site had long life and which did not undergo chain transfer. Therefore, they approximate many of the characteristics of living polymers.     

Polymerization of ethylene with the (C5H5)4Zr-methylaluminoxane soluble catalytic system

The effects of catalyst concentration, Al-to-Ti molar ratio, hydrogen additives, and time of aging of catalyst components on the kinetic features of ethylene polymerization in the presence of the (C₅H₅)₄Zr-methylaluminoxane soluble catalytic system in toluene and hexane at 60°C and an ethylene pressure of 0.6 MPa have been studied. It has been demonstrated that the highest activity and productivity of the title system is achieved in the presence of 0.9% H₂ in the gas phase of a reactor (2180 kg PE/(g Zr h)). When polymerization is carried out in hexane, the rate constant of chain propagation is lower by a factor of ～1.5 than that in the case of toluene and the catalytic system is characterized by a long lifetime.