Isabella Camurati

• LyondellBasell Industries

A study of the crystallization behavior and mechanical properties of random isotactic butene-ethylene copolymers prepared with a metallocene catalyst is presented. The use of the metallocene catalysis ensures a fine control over the molecular structure with low concentration of rr stereodefects (0.8%), negligible amount of regiodefects, and random...

A structural characterization of samples of isotactic propylene−butene copolymers (iPPBu), synthesized with a metallocene catalyst, is reported. The copolymers crystallize in the entire range of comonomer compositions, and α and γ forms of isotactic polypropylene (iPP) crystallize in propene-rich copolymers, whereas form I of isotactic polybutene (...

The aim of this work was to study the comonomer distribution and the chemical composition distribution generated by different Ziegler-Natta (ZN) systems (different internal donors, ID, dicyclopentadienyl-dimethoxy silane, D donor, as the external donor) and to define the potentialities of different IDs to produce improved heterophasic copolymers (H...

Polypropene and poly(1-butene) have been synthesized under very similar experimental conditions with a series of MAO-activated C2-symmetric and C1-symmetric ansa-zirconocenes. The C1-symmetric zirconocenes bearing the bilaterally symmetric fluorenyl or bis(2-methylthieno)cyclopentadienyl ligand connected through a dimethylsilyl bridge to substitute...

Random copolymers of propylene with ethylene, butene, and hexene comonomers have been prepared with different metallocene catalysts. The used catalysts have allowed a precise control of concentration of stereodefects and high degree of comonomer incorporation while maintaining high molecular mass and random distribution of comonomers. Incorporation...

Isotactic propylene−ethylene (iPPEt) and propylene−butene (iPPBu) copolymers have been prepared with different metallocene catalysts. The different influences of stereodefects (isolated rr triads), ethylene and butene comonomeric units on the crystallization of the α and γ forms of isotactic polypropylene (iPP) have been discriminated. Both iPPEt a...

Isotactic polybutenes of variable isotacticity and melting points of form I in the range 100–125 °C have been prepared with both C 2 ‐ and C 1 ‐symmetric zirconocenes. The C 1 ‐symmetric zirconocenes bearing the bilateral symmetric 2,5‐dimethyl‐7 H ‐cyclopenta[1,2‐b:4,3‐b′]dithiophene ligand connected by a dimethylsilandiyl bridge to a substituted...

The acid-catalyzed reaction between formaldehyde and 1H-indene, 3-alkyl- and 3-aryl-1H-indenes, and six-membered-ring substituted 1H-indenes, with the 1H-indene/CH2O ratio of 2 : 1, at temperatures above 60° in hydrocarbon solvents, yields 2,2′-methylenebis[1H-indenes] 1–8 in 50–100% yield. These 2,2′-methylenebis[1H-indenes] are easily deprotonate...

The most advanced catalysts, based on MgCl2-supported TiCl4 and electron donors, are able to provide polypropylenes with an isotacticity higher than 99%. This, together with the continuous progress made in understanding and exploiting the role of electron donors in controlling polymer MW and MWD, has led to polypropylene products having an unpreced...

Reaction between 7-azaindole and B(C6F5)3 quantitatively yields 7-(C6F5)3B-7-azaindole (4), in which B(C6F5)3 coordinates to the pyridine nitrogen of 7-azaindole, leaving the pyrrole ring unreacted even in the presence of a second equivalent of B(C6F5)3. Reaction of 7-azaindole with H2O-B(C6F5)3 initially produces [7-azaindolium]+[HOB(C6F5)3]- (5)...

Highly isotactic polypropylene samples, containing a very low amount of rr stereodefects (0.1−0.2%) and slightly higher concentration of defects of regioregularity (0.8−0.9% of 2,1 erythro units), with different molecular masses have been prepared with an isospecific but not fully regioselective metallocene catalyst. The effects of the presence of...

Simple synthetic routes to the first borinatoborate anion [(C6F5)3BOB(C6F5)2]- and to the previously known [(C6F5)3B(μ-OH)B(C6F5)3]- and [(C6F5)3BO(H)H···O(H)B(C6F5)3]- diborate anions have been developed. The X-ray analysis of the latter species provided the first experimental observation of an asymmetric H-bond in the [H3O2]- moiety. No evidence...

Sixteen C 1 ‐symmetric zirconocene and one hafnocene complexes bearing the 2,5‐R 2 ‐7H‐cyclopenta[1,2‐ b :4,3‐ b ′]dithiophene ligand (R = H, Me, Et, Ph) linked to a substituted indenyl ligand have been synthesized and tested in propylene polymerization. Most of the C 1 ‐symmetric zirconocenes of this type are highly active in propylene polymerizat...

A series of MAO-activated C(1)-symmetric indenyl-ansa-dithienocyclopentadienyl-based zirconocenes have been used to produce isotactic polypropylenes of medium to high molecular weights, of different degrees of stereoregularity, and free from regioerrors. The effect of the presence of rr defects on the polymorphic behavior and mechanical properties...

The synthesis of C 1 ‐symmetric zirconocene complexes bearing the 2,5‐dimethyl‐7 H ‐cyclopenta[1,2‐ b :4,3‐ b ′]dithiophene ligand ( S 2 ‐3 ) linked to substituted cyclopentadienes is described. Different syntheses of S 2 ‐3 , the common intermediate for the preparation of these complexes, are discussed. Many of these complexes have been found to b...

The stoichiometric reactions of N-methylpyrrole and N-methylindole with B(C6F5)3 produce the zwitterionic species 2-[tris(pentafluorophenyl)borane]-5H-1-methylpyrrole (3) and 2-[tris(pentafluorophenyl)borane]-3H-1-methylindole (4), in which a C(α)−B bond and an acidic sp3 methylene carbon are formed in the heterocyclic part of the molecule. Both de...

Stereoblock, isotactic‐hemiisotactic poly(propylene) is produced with C 1 ‐symmetric Me 2 C( η ⁵ ‐3‐(2‐adamantyl)‐C 5 H 3 )( η ⁵ ‐C 9 H 4 S 2 )ZrCl 2 ( 1 ). Ethylene/propylene copolymerization data with the C s ‐symmetric Me 2 C( η ⁵ ‐C 5 H 4 )( η ⁵ ‐C 9 H 4 S 2 )ZrCl 2 ( 2 ) metallocene reveals that it is highly propylene‐specific and that it prod...

The reaction of pyrroles and indoles with perfluoroarylboranes produces 1:1 B‐N complexes that contain highly acidic sp ³ methylenes. These complexes are stable and can be used as a proton source for the generation of methylmetallocene cations. Indole is preferred over pyrrole. The 1:1:1 borane:indole:dimethylmetallocene compositions are, in some i...

Indenyl silyl amido titanium complexes based on indenoindoles, indenopyrrole, and 2-methylindenothiophene have been prepared and tested in propylene polymerization. The indenoindole ligand precursors were prepared in high yields by the acid-catalyzed Fischer condensation of indan-2-one and arylhydrazines. The Ti complexes dimethylsilyl(tert-butylam...

Ethanol associates easily with MgCl(2) to form adducts of complex architecture, but until now available characterization methods have failed to identify the pure stoichiometric compounds and their structures. To remedy this, we set about applying homonuclear and heteronuclear 2D correlated solid-state NMR spectroscopy to identify the pure compounds...

Heterocycle-fused titanium indenyl silylamido dimethyl complexes produce very high molecular weight polypropylene having a prevailingly syndiotactic microstructure with syndiotactic pentad contents rrrr up to 40-55% (sam-PP). The samples are basically amorphous and may slowly develop a low level of crystallinity (16-20%) at room temperature. A stru...

The use of bisindenyl zirconium dimethyl in the synthesis of the corresponding dihalides is described. The synthesis of Ind2ZrCl2 has been carried out, cleanly and quantitatively, by chlorination of Ind2ZrMe2 (2) with a variety of inorganic chlorides, including BCl3, SCl2 in either toluene or methylene chloride, and HCl in Et2O. The latter method i...

The reaction of pyrroles and indoles with B(C(6)F(5))(3) and BCl(3) produces 1:1 B-N complexes containing highly acidic sp(3) carbons, for example, N-[tris(pentafluorophenyl)borane]-5H-pyrrole (1) and N-[tris(pentafluorophenyl)borane]-3H-indole (2), that are formed by a new formal N-to-C hydrogen shift, the mechanism of which is discussed. With som...

The chemical composition distribution (CCD) of LLDPE (1‐butene comonomer) has been studied by thermal analysis. After an opportune thermal treatment of the polymers, thermal fractionated crystallization (TFC), the melting endotherms have been subdivided in areas with fixed temperature ranges. The distribution of the endotherms in different areas ga...

The synthesis of a series of indenyl amido titanium dimethyl complexes, by means of the direct synthesis from the ligand, a 2-fold excess of MeLi, and TiCl4 is reported. The 1H NMR spectra of the complexes show a quartet structure for the metal-bound methyl groups, due to through-metal proton–proton coupling. Coupling of Ti-methyl protons with prot...

Low-temperature (220−290 K) ethylene-ran-propylene copolymer crystallization was followed by DSC and solid-state NMR spectroscopy that can detect the formation of even small and short-living crystalline aggregates (minimum lifetime of 3 ms). NMR at 282 K reveals a sharp and reversible melting−crystallization transition in the copolymer with 74% eth...

Group 4 dimethylmetallocenes are catalyst precursors for the methylmetallocenium/borate catalyst systems for olefin polymerization, and they are usually prepared by methylation (with MeMgCl or MeLi) of the parent metallocene dichlorides. We describe here a simpler preparation of a series of bisindenyldimethylmetallocenes carried out by reacting the...

Poly(propylene)s prepared using MgCl2-supported catalysts containing different electron donors have been characterized using temperature rising elution fractionation (TREF), gel permeation chromatography (GPC) and 13C NMR analysis. In addition, the regio- and stereochemical composition of oligomeric fractions present in selected polymers has been d...

Poly(propylene)s prepared using MgCl2-supported catalysts containing different electron donors have been characterized using temperature rising elution fractionation (TREF), gel permeation chromatography (GPC) and 13C NMR analysis. In addition, the regio- and stereochemical composition of oligomeric fractions present in selected polymers has been d...

Details of the preparation and polymerization behavior of two chiral zirconocene catalysts are presented. The results of experimental and molecular-mechanics evaluation of their stereoselectivity with respect to liquid-propene polymerization are compared with those of a related catalyst system. The elastic properties of the obtained amorphous poly(...

Ethene/propene copolymerizations were performed with rac-[ethylenebis(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride (r-EBTHIZrCl2) and tetraisooctylaluminoxane (TIOAO). Copolymerizations were carried out at three levels of comonomer concentrations, in a range from about 0.011 M to about 2.6 M. The reactivity ratios of copolymerizations (r11, r...

The catalytic system rac-Me2Si(Ind)2ZrCl2/MAO was used to polymerize ethylene and to copolymerize ethylene with different 1-olefins (copolymers containing 1-olefins up to 1-tetradecene were prepared). In the presence of the 1-olefin, the catalytic activity increases. As expected, the amount of 1-olefin inserted in the polymer chain depends on the m...

Seven samples of isotactic polypropylene were examined to study the influence on the formation of the γ crystalline phase of possible regiodefects along the chain. Wide-angle X-ray diffraction allowed the determination of the percentage of the γ phase in the samples and 13C-NMR spectroscopy was used to correlate the development of the γ phase with...

The influence of polymerization temperature, propylene concentration and hydrogen on the polymerization performance of the isospecific, highly regiospecific rac-Me2C(3-t-Bu-1-Ind)2ZrCl2 / MAO (1/MAO) catalyst has been investigated. Propagation follows the rate law Rp = (a[M]+b[M]²)/(c+d[M]). 1/MAO is more stereospecific compared to unsubstituted bi...

Ethene/propene copolymerizations were performed with catalytic systems composed of a stereorigid racemic isospecific metallocene and polymethylalumoxane. A number of complexes were used as representatives of three different classes of metallocenes. r-Me2C(3-t-Bu-Cp)2ZrCl2, r-Me2C(3-t-Bu-Ind)2ZrCl2, r-EBDMIZrCl2, r-EBDMTHIZrCl2, and r-Me2Si(2-Me-4-P...

Ethene/propene copolymerizations were performed in solution with a single centre catalyst system composed of a “constrained geometry” half-sandwich organometallic complex {η1: η5-[(tert-butylamido)dimethylsilyl](2,3,4,5-tetramethyl-1-cyclopentadienyl)}titanium dichloride, and methylaluminoxane. The statistical treatment of polymerization data allow...

The new compound meso-ethylenebis (4,7-dimethyl-1-indenyl) zirconium dimethyl (1-Me2) has been prepared and a detailed structural investigation by 2D-NMR has been performed, using COSYgs, NOESY, HBMCgs and HSQCgs spectra. These experiments allowed us to perform the full 1H and 13C NMR spectral assignments. We also detected long distance interaction...

The chemical structures of end groups of medium-low molecular weight atactic and isotactic polypropylenes (a-PP and i-PP), produced with zirconocene/methylalumoxane catalysts, have been analyzed and used to infer the chain-transfer reaction mechanisms, which are then correlated with the zirconocene ligand structure and the polymerization conditions...

A new alumoxane alternative to MAO was synthesised, characterized and used as cocatalyst for metallocene based polymerizations. It is based on Al(2,4,4-trimethylpentyl)3 (TIOA). Alumoxanes were prepared by reacting TIOA and H2O with different molar ratios. 1H NMR spectra of these products are characterized by the presence of broad bands and of reso...

Ethene/propene copolymerizations were performed with a catalytic system composed of a metallocene and an alumoxane. The role played by the alumoxane was investigated by comparing the effects of three different compounds:  poly(methylalumoxane) (MAO), tetraisobutylalumoxane (TIBAO), and tetraisooctylalumoxane (TIOAO). A thorough comparison was perfo...

This paper will discuss the role of organometals in the production of elastomeric copolymers of ethylene, propylene and a diene (EPDM). Catalyst technologies based on vanadium and titanium will be compared, and the properties of resulting products are illustrated.

Ethene and propene were copolymerized using a metallocene-based catalytic system, composed of rac-isopropylidenebis(3-tert-butylcyclopentadienyl) zirconium dichloride, and poly(methylalumoxane) (MAO). Ethene/propene copolymers were prepared in a broad range of chemical composition, from 17% to 92% as ethene molar content. The use of an isospecific...

A new class of isospecific and highly regiospecific C2-symmetric ansa-zirconocenes, characterized by a bisindenyl ansa ligand with bulky substituents in the 3 position of indene and a single carbon bridge is disclosed:  variation of the size of the substituent in C(3) has a strong effect on the extent of chain transfer and isospecificity in propene...

The behavior in propylene polymerization of divalent titanium compounds of type [η6-areneTiAl2Cl8], both as such and supported on activated MgCl2, has been studied and compared to that of the simple catalyst MgCl2/TiCl4. Triethylaluminium was used as cocatalyst. The Ti–arene complexes were active both in the presence and in the absence of hydrogen,...

The known rac-[ethylenebis(4,7-dimethyl-η5-1-indenyl)]ZrCl2 (2r) and its meso isomer (2m) have been compared with the prototypal chiral isospecific rac-[ethylenebis(η5-1-indenyl)]ZrCl2 (1r) and its aspecific meso isomer 1m in terms of molecular structures, solution dynamics, and ligand substitution effect on polymerization performance. In liquid pr...

The microstructure in terms of molecular mass distribution (MMD) and chemical comonomer distribution (CCD) of linear low density polyethylene (LLDPE) is greatly influenced by the catalytic system and process conditions. Furthermore, the 1-olefin insertion in the polymer chain can be distinguished between intramolecular and intermolecular distributi...

The recent discovery of homogeneous metallocene-based Ziegler-Natta catalysts has led to the synthesis of EP copolymers with new comonomer and stereochemical structures. In the present paper C-13 NMR investigation of EP copolymers at high ethylene content, prepared with highly isospecific, highly syndiospecific, and aspecific catalysts, is presente...

The crystal and molecular structures of the C-2 symmetric rac-(EBI)ZrCl2 (1r) [monoclinic, space group I2/c, No. 15, a = 11.957(1) Angstrom, b = 10.627(1) Angstrom, c = 13.775(2) Angstrom, beta = 106.06(1)degrees] and of its meso isomer (1m) [monoclinic, space group P2(1)/n, No. 14, a = 11.119(3) Angstrom, b = 10.467(1) Angstrom, c = 14.949(2) Angs...

In this paper, new polyolefin elastomers, obtained from metallocene based catalytic systems, are presented. The potentialities of metallocenes for the preparation of polyolefin elastomers are discussed with reference to the traditional vanadium and titanium based catalysts. The role played by a Ziegler - Natta catalyst, either stereospecific or asp...

Solid-State 1H-NMR measurements of T1 relaxation times performed on polycarbonate-poly(ethyleneterephthalate) (PC–PET) blends point out the presence of two separate domains with apparent dimensions of about 80 nm. The variation of PET domain relaxation time with the increase of PC content is explained in terms of an interface in which parts of the...

The study of water relaxation rates of solutions of melanins with paramagnetic metal ions provides a powerful tool for investigating the binding sites and for obtaining useful structural and dynamic information. The measure of 1H- and 2H-longitudinal and transverse relaxation rates at a single, high-magnetic field for H2O/D2O (80:20) solutions allo...