Polymers from pine gum components: Radical and coordination homo and copolymerization of pinenes

The present work is aimed at studying the reactivity of α- and β-pinenes in radical polymerization. The pinene homopolymers obtained were oligomers, showing both isomers similar reactivities. In order to achieve products of higher molecular weight, the radical copolymerization of α- and β-pinene with methyl methacrylate and styrene was performed, giving rise to polymers with M̄_w varying from 11 500 to 53 000. In radical copolymerization α-pinene showed to be more reactive than β-pinene. All the radical reactions performed were carried out with a Ziegler-Natta catalyst, TiCl₄/Et₃Al, and with Et₃Al. Under the conditions tested, β-pinene did not undergo any polymerization reaction and the cocatalyst showed a pronounced catalytic effect. The coordination polymers obtained at 5 h had chain lenghts of the same order of magnitude of the corresponding radical copolymers obtained at 50 h, although for much lower overall conversion.     

Synthesis and Characterization of Poly(vinyl Chloride-g-α-Methylstyrene)- A New Thermoplastic Resin. 2

α-Methylstyrene was grafted on PVC using alkylaluminum Et₂AlCl, Et₃Al, and Me₃Al coinitiators and CH₂Cl₂ as solvent or suspending agent. Grafting was shown to be feasible using both solution and suspension techniques. High grafting efficiency and low monomer conversion were obtained using Et₃Al and Me₃Al, while low grafting efficiency but high conversion could be obtained using Et₃AlCl coinitiator. This paper discusses the synthesis, characterization and some mechanical properties of α-methyl-styrene grafted PVC.     

Cyclopropanation of alkenes with CH2I2/Et3Al by the phase-vanishing method based on fluorous phase screen

Phase-vanishing (PV) method using perfluorohexanes as a screen phase was applied to cyclopropanation reactions with CH₂I₂/Et₂Zn and CH₂I₂/Et₃Al. When Et₃Al was used as a carbenoid generator, the reaction proceeded smoothly and desired cyclopropane derivatives were obtained in high yield. The PV cyclopropanation took 2 or 3 days to complete, however, reduction of reaction time by a factor of 2-3 was also achieved by vigorous stirring after the bottom CH₂I₂ layer disappeared.     

ZrCl4-Catalyzed scission of ethylene acetals with organoaluminum compounds

Ethylene acetals and ethylene ketals undergo reductive scission under the action of Buⁱ ₂AlH in the presence of catalytic amounts of ZrCl₄. With Et₃Al and Buⁱ ₃Al, reductive alkylation also occurs. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1550–1552 August, 1999.     

Aluminum carbenoids in the cyclopropanation of fulvenes

Aluminum carbenoid Et₂AlCH₂I reacts with 6-substituted fulvenes to give tricyclopropanes in high yields. Calculations at the B3LYP/6-31G(d) level of theory show that coplanar arrangement of the double bonds facilitates cyclopropanation due to conjugation in the transition state. Aluminum carbenoid Et₂AlCH₂I was generated by either the reaction of equimolar amounts of Et₃Al and CH₂I₂ in hexane or treatment of Et₂AlI with CH₂N₂ in dichloromethane.     

Caewoalljmination of Diphenylacetylene

It was found that diphenylacetylene reacts at 90[ddot]C with Et₃Al to form cis-ethylvinylalane. On the other hand, Et₃Al adds mostly in an anti-manner to diphenylacetylene at 140°C.     

Tandem asymmetric conjugate addition-enolacetates formation of enantiomerically enriched zinc and aluminium enolates

The metal enolates, resulting from the copper-catalyzed enantioselective conjugate addition of organometallic reagents (Et₂Zn or R₃Al) to cyclic and acyclic enones are quantitatively trapped as enolacetates with acetic anhydride.     

Stereoregular polymerization of 1-vinylnaphthalene, 2-vinylnaphthalene,and 4-vinylbiphenyl

1-Vinylnaphthalene, 2-vinylnaphthalene, 4-vinylbiphenyl, and styrene were polymerized with Et₃Al–TiCl₄, Et₂AlCl–TiCl₃, and Et₃Al–TiCl₃ catalyst systems. The latter catalyst system gave polymers in 75–95% conversion which were at least 90% isotactic. Extraction with 2-butanone (MEK) separated the atactic from the isotactic fractions. The polymers were characterized by infrared and nuclear magnetic resonance spectroscopy.     

The reactions of nickel(II) carboxylates with a series of ethylaluminum chlorides

The distribution of nickel in the reaction products from the reactions of nickel(II) stearate with diethylaluminum chloride (Et₂AlCl), ethylaluminum sesquichloride (Et₃Al₂Cl₃), and ethylaluminum dichloride (EtAlCl₂) in benzene was investigated as a function of the Al/Ni reaction stoichiometry. The products consist of benzene-soluble nickel complexes and a precipitate from which can be extracted NiCl₂ and metallic nickel. The percentage of each product is seen to be dependent upon the Al/Ni reaction ratio and the aluminum compound employed in the reaction. It was found that in each case six alkylaluminums are required for complete reaction with one nickel(II) stearate molecule. The compunds Et₂AlCl, Et₃Al₂Cl₃, and EtAlCl₂ were all found to have greater reducing ability than Et₃Al at room temperature. Alternative interpretations of the chloro compounds' greater reducing abilities are discussed.     

Chlorotitanium (IV) tetradentate Schiff‐base complex immobilized on inorganic supports: Support type and other factors having effect on ethylene polymerization activity

A titanium complex with [O,N,N,O]‐type tetradentate Schiff base (LTiCl₂), never used before in polymerization of olefins, was immobilized on silica‐ and magnesium‐type carriers, and it was used in ethylene polymerization. The conducted research revealed that the catalytic properties of the complex LTiCl₂ supported on those carriers were different for both the catalytic systems studied, and simultaneously they turned out different from those of the unsupported system. The supported catalysts require the use of Me₃Al, Et₃Al, or MAO as the activator to be able to offer high catalytic activities, whereas Et₂AlCl is needed for the nonsupported catalyst. This finding, together with considerable changes in polymerization yields and in properties of polymers versus composition of the catalytic system, suggest that there are different types of active sites in the studied catalysts. The catalyst anchored on the carrier produced in the reaction of MgCl₂·3.4EtOH with Et₂AlCl is definitely the most active one within the support systems tested. Its activity remarkably increases with the increasing reaction temperature. Moreover, that catalyst does not undergo deactivation over the studied period of time, irrespective of the type of the activator used and of the process temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4811–4821, 2009     

Ethylene polymerization initiated by metallocene catalysts (C5H5)4Mt-MAO (Mt = Ti, Zr) in the presence of organometallic modifiers

The effect of various organometallic compounds (Me₃Al, Et₃Al, i-Bu ₃Al, Et₂Zn, Me₄Sn, Et₄Pb) on the activity and productivity of catalytic systems based on (C₅H₅)₄Zr and (C₅H₅)₄Ti and the molecular- mass characteristics of polymers is investigated. The effect of additives on the activity of catalysts; on the shape of kinetic curves of polymerization; and on the molec ular mass, molecular-mass distribution, and poly- dispersity of the resulting polymers is associated with reversible chain transfer to the organometallic compounds.     

Electrodeposition of Aluminum from AlCl3/Et3NHCl Ionic Liquids

Aluminum was successfully electrodeposited on Al electrodes from aluminum chloride (AlCl₃)/triethylamine hydrochloride (Et₃NHCl) ionic liquids by the constant potential electrolysis. Electrical conductivities of AlCl₃/Et₃NHCl ionic liquids were measured as a function of the temperature and composition. The nucleation processes and the influence of experimental conditions on the current efficiency and surface morphology of aluminum electrodeposits were studied on Al electrodes from 2:1 molar ratio AlCl₃/Et₃NHCl ionic liquid. The electrical conductivities of ionic liquids increased as the electrolyte temperature increased, following the Arrhenius behavior. Analyses of the chronoamperograms indicated that the deposition process of aluminum on Al substrates was controlled by instantaneous nucleation with diffusion-controlled growth. Constant potential deposition experiments showed that the electrodeposits obtained on Al electrodes were dense, continuous, and well adherent, and the current efficiency was 73% at −2.4 V(vs Pt) for 20 min electrolysis at room temperature. The purity of aluminum electrodeposits on Al electrodes was above 96% (w).     

Chalcogenolato-di-thiocarbamato-complexes of zinc: The X-ray single crystal structures of pyridine adducts

Novel mixed complexes 2,4,6-Me₃C₆H₂SZnS₂CNEt₂ (1), 2,4,6-Me₃C₆H₂SeZnSe₂CNEt₂ (2) and their pyridine adducts ([Zn(SC₆H₂Me₃-2,4,6)₂(C₅H₅N)₂] (3), [Zn(SeC₆H₂Me₃-2,4,6)₂(C₅H₅N)₂] (4) and (Et₂CNSe₂)₂Zn.NC₅H₅ (5) and (Et₂CNS₂)₂Zn.NC₅H₅ (6) have been synthesised and characterised. The X-ray single crystal structures of (4), (5) and (6) have been determined.     

Synthesis and transformations of metallacycles 42. Cp2ZrCl2-Catalyzed cycloalumination of 3-methylidenespiro[cyclobutane-1,3′-(5′α)-cholestane] with Et3Al

A Cp₂ZrCl₂-catalyzed cycloalumination of 3-methylidenespiro[cyclobutane-1,3′-(5′α)-cholestane] with Et₃Al gives 3-ethyl-3-aluminadispiro[cyclopentane-1,1′-cyclobutane-3′,3″-(5″α)-cholestane] in 84% yield.     

CIDNP study of the Ni(acac)2-catalyzed reaction of triethylaluminum with chloroform

CIDNP effects were found in the Ni(acac)₂-catalyzed reaction of Et₃Al with CHCl₃. The effects appear in the products of transformation of the diffusion radical pair of the ethyl and dichloromethyl radicals. The radical route is a side process in this reaction, and the main products, Et₂AlCl, ethane, and ethylene, are formed by a nonradical route. A general mechanism of the reactions of Et₃Al with CHCl₃ and CCl₄ including radical and ioncoordination processes was suggested. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1003–1006, May, 1999.     

Chlorobis(polyfluorophenyl)thallium(III) complexes and their reactions with gold(I) and tin(II) compounds

The reaction of TlCl₃ with RLi leads to complexes of the general formula TlR₂Cl (R = C₆F₅, p-C₆F₄H, m-C₆F₄H, 2,4,6-C₆F₃H₂, p-C₆FH₄ or m-CF₃C₆H₄). Some of these undergo oxidative addition reactions with gold(I) complexes to give polyfluorophenyl derivatives of the types AuR₂ClL and Au(C₆F₅)R₂(tht) (tht = tetrahydrothiophen), and with SnCl₂ to give oily materials from which stable solids of the general formula Q[SnR₂Cl₃] can be isolated by addition of QCl (Q = Et₄N or Ph₃BzP).     

The effect of cocatalysts on the oligomerization and cyclization of ethylene catalyzed by zirconocene complexes

Under certain conditions (150°C, P(C₂H₄)=1.4 MPa), the oligomerization of ethylene catalyzed by Cp₂ZrCl₂/EAO (ethylaluminoxane), Et₃Al or (i-Bu)₃Al afforded methylenecyclopentane (MCP) along with chain oligomers. The nature of cocatalysts and the Al/Zr ratios as well as the hydrolysis extent of Et₃Al have tangible effects on the selectivity of the cyclic oligomer. With Et₃Al as cocatalyst under optimal conditions, the oligomerization of ethylene gave MCP and C₄–C₁₀ chain olefins in a ratio of 45/55.

Full-size image (2K)

Reductive pinacol-type rearrangement of chiral α-mesyloxy ketones promoted by organoaluminum compounds

Reductive pinacol-type rearrangement of chiral α-mesyloxy ketones was effected by organoaluminums (DIBAL in combination with Et₃Al or Et₂AlCl) leading to enantiomerically pure 2-aryl- or 2-alkenyl-1-propanols.     

Organic base catalyzed carbonyl allylation of methyl trifluoropyruvate with activated alkenes

The carbonyl allylation of methyl trifluoropyruvate (MeTFP) with activated alkenes has been investigated in detail using organic bases as catalysts. Organic bases, such as DMAP, Et₃N, DABCO, NMM, Et₂NH, and quinine, could deprotonate the allylic hydrogen of activated alkenes and furnish nucleophilic species to undergo the addition reaction with methyl trifluoropyruvate and afford versatile homoallylic alcohols with CF₃ group in excellent yields. The ¹⁹F NMR monitoring indicated that the isomerization induced by base gave two separable diastereoisomers in an equilibrium ratio of 1:3. The relative configuration of hydroxy and the neighboring alkyl group in the major diastereoisomer was determined as syn-configuration by X-ray diffraction analysis.     

Cycloaluminizing of Acetylenes and 1,4-Enynes in the Presence of Zr-containing Catalysts

Synthetic procedures were developed for preparation of substituted alumacyclopenta-2,4-dienes and 1-ethyl-2(3)-(1-ethyl-3-alumacyclopentylmethyl)-3(2)-alkyl(phenyl)alumacyclopent-2-enes by cycloaluminizing acetylenes and 1,4-enynes using RAlCl₂ (R = Et, BuO, Et₂N) and Et₃Al in the presence of Zr-containing catalysts (Cp₂ZrCl₂, ZrCl₄).__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 684–689.Original Russian Text Copyright © 2005 by Dzhemilev, Ibragimov, Khafizova, Yakupova, Khalilov.