Cyclo- and Cyclized Diene Polymers. XXII. Kinetics of Cyclopolymerization of Isoprene with C2H5AlCl2 + TiCl4 Catalyst

The polymerization of isoprene in aromatic solvents, catalyzed by an ethylaluminum dichloride-titanium tetrachloride system, proceeds via a complex of the monomer with the catalyst, chain growth occurring when a monomer cation-radical is formed through the transfer of one electron from the monomer to the catalyst. The deactivation of the active species results from the dissociation of the complex polymer cation-radical to free ions. The over-all reaction is a nonstationary process during which the concentration of free ions increases and the concentration of the active species decreases. A reaction mechanism is proposed which leads to kinetic expressions that quantitatively describe the experimental data.     

FT-Infrared and FT-Raman Spectroscopic Studies of Complexes (C5H5)2TiCl2,(C5H4Me)2TiCl2 and (C5HMe4)2TiCl2

IntroductionThe accidental discovery of ferrocene, (C,H,)ZFe, has been well recognized as a majorcause of the subsequent explosive growth of organometallic chemistry['--'1. Metallocenes havebecome the most famous organometallic compounds. Recently, a considerable attention hasbeen given to the study of the vibrational spectra of metallocenes and the complexes containingthe M-(f-C,H,) unit. The problems concerning the spectroscopy and the structure of cyclopentadienyl complexes have been dis…     

The morphology of nascent polyethylene prepared with the soluble catalyst (C5H5)2TiCl2-R2AlCl

Summary Polyethylene was prepared with the solubleZiegler-Natta catalyst bis-(cyclopentadienyl)-titanium dichloride-dialkylaluminum chloride under various polymerization conditions. The morphology and properties of the nascent polymer samples were studied by electron microscopy, fuming nitric acid oxidation and differential scanning calorimetry. The observations show that the polymer has a chain-folded lamellar structure. The morphology of this polymer contrasts with the fibrillar texture of nascent poly(α-olefins) prepared with heterogeneousZiegler-Natta catalysts. It is suggested that inZiegler-Natta polymerizations the morphology of the nascent polymer is determined by the physical state of the catalyst in the polymerization medium.

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Zusammenfassung Poly?thylen wurde unter verschiedenen Polymerisierungsbedingungen mit dem l?slichenZiegler-Natta-Katalysator Bis-(cyclopentadienyl)-Titandichlorid-Dialkylaluminiumchlorid hergestellt. Die Morphologie und Eigenschaften der naszierenden Polymerproben (imstatus nascendi) wurden durch Elektronenmikroskopie, Oxidation mit rauchender Salpeters?ure und kalorische Messungen untersucht. Die Beobachtungen zeigen, da? die polymere Substanz eine kettengefaltete lamellare Struktur hat. Die Morphologie dieses Polymeren unterscheidet sich von der fibrillaren Textur der naszierenden Poly(α-olefine) die durch heterogeneZiegler-Natta-Katalysatoren hergestellt wurden. Es wird vorgeschlagen, da? man fürZiegler-Natta-Polymerisate die Morphologie durch den physikalischen Zustand des Katalysators im Polymerisierungsmedium imstatus nascendi untersucht.

     

Arrhenius parameters for the reactions CH3. + C4H10 → CH4 + C4H9. and C2H5. + C4H10 → C2H6 + C4H9.

Study of n-butane pyrolysis at high temperature in a flow system allows measurement of the sum of the rate constants of the initiation reactions and of the Arrhenius parameters of the reactions Established data for k₁/k₂ allow estimation of k₁ for 951°K and this, with recent thermochemical data, yields the result log k_?1 (l.mole s^?1) = 8.5, in remarkable agreement with a recent measurement [20] but over si×ty times smaller than conventional assumption. The product k₃k₄ (l.²mole^?2s^?2) is found to be associated with the Arrhenius parameters log (A₃A₄) = 21.90 ± 0.6 and (E₃ + E₄) = 38.3 ± 2.7 kcal/mole. These values are much higher than would be e×pected on the basis of low temperature estimates. Independent evaluation gives log A₄ = 10.5 ± 0.4 (l.mole^?1s^?1) and E₄ = 20.1 ± 1.7 kcal/mole, hence log A₃ = 11.4 ± 0.8 (l.mole^?1s^?1) and E₃ = 18.2 ± 3.2 kcal/mole. These values are shown to be entirely consistent with a wide range of results from pyrolytic studies, and it is argued that they further confirm the view that Arrhenius plots for alkyl radical–alkane metathetical reactions are strongly curved, in part due to tunneling and, appreciably, to other as yet unidentified effects. Since there is published evidence that metathetical reactions involving hydrogen atoms show even greater curvature, it is suggested that this may be a characteristic of many metathetical reactions.     

Syntheses and crystal structures of [(C6H5CH2C5H4)2GdCl.THF]2 and (C6H5CH2C5H4)2ErCl.THF

[(C₆H₅CH₂C₅H₄)₂GdCl.THF]₂ (1) and (C₆H₅CH₂C₅H₄)₂ErCl.THF (2) were prepared by the reaction of LnCl₃ (Ln? Gd, Er) with benzylcyclopentadienyl sodium in THF and characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, MS and thermal gravimetry. The crystal structures of both compounds were determined. Complex 1 is dimeric and its structure belongs to the monoclinic, P2₁/c space group with a=1.1432(2), b=1.2978(2), c=1.7604(3) nm, β=108.75(2), V=2.4732(9) nm³, Z=2(four monomers), D_c“1.54 g.cm^?3. R=0.0342 and R_w“0.0362. Complex 2 is monomer and its structure belongs to the orthorhombic, P2₁2₁2₁ space group with a=0.8645(2), b=1.1394(3), c=2.5289(4) nm, V=2.4919(9) nm³, Z=4, D_c“1.56 g.cm^?3. R=0.0514, R_w“0.0529. The determination of the crystal structure shows that in complex 1 the benzyl groups on the cyclopentadienyls coordinated to Gd³⁺ are located in the opposite direction (139°); in complex 2 the benzyl groups on the cyclopentadienyls coordinated to Er³⁺ are located in the same direction (6.5°).     

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.