Zirconium Metallocenes Research Articles

Synthesis of the bimetallic zirconium compound derived from unsubstituted as-indacene and its catalytic behavior on ethylene polymerization

This contribution describes the synthesis and characterization of bimetallic zirconium metallocene derived from unsubstituted 1,8-dihydro-as-indacene (as-IcH2). The complex [(Cp*ZrCl2)2-as-Ic] was synthesized from the dilithiated salt of as-indacene [as-Ic][Li]2 with two equivalent of [(Cp*ZrCl3)]. This complex here reported was characterized by means of 1H and 13C NMR, elemental analysis, and X-ray diffraction. In order to gain further knowledge about their catalytic behavior, the complex was tested in the catalysis of ethylene polymerization showing a highest activity. Theoretical calculations of zirconium compound were carried out to benefit additional understanding the mechanism of this novel olefin catalyst.

Zirconium Catalyzed Transformations Using Organoboron

AbstractOrganoboron compounds have extreme potential for organic synthesis. Ready functionalization of organoboron intrigued people to develop various protocols for their synthesis. Over the last several decades, there has been a substantial development in synthesizing new organoboron compounds using transition metals. Among various transition metals, zirconium has also been found to catalyze diverse reactions of organoboron. The zirconium chemistry has become more popular with the development of zirconium metallocenes, particularly bis(cyclopentadienyl)zirconocene chloride hydride, the well‐known Schwartz reagent. These zirconium metallocenes possess a significant role in hydrozirconation, hydroboration, hydrogenation, carbozirconation, and a promising tri‐n‐butyl tin hydride alternative. This minireview focuses on the various transformations of organoboron employing zirconium catalysts that have been developed so far.

Ancillary ligand effects on α-olefin polymerization catalyzed by zirconium metallocene: a computational study.

The polymerization of α-olefins catalyzed by zirconium metallocene catalyst was systematically studied through experiments and density functional theory (DFT) calculations. Having achieved an agreement between theory and experiment, it was found that the effect of the catalyst ligand on the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C insertion reaction was significantly greater than that on the β-H elimination reaction. Therefore, the molecular weight of polymers can be increased by improving the activity of the CC insertion. In addition, in comparison with propylene, the chain length of α-olefins can directly affect the stereotacticity of polymerization products, owing to steric hindrance between the polymer chain and monomer.

A new series of zirconium metallocenes derived from partially alkylated s-indacene with potential applications in the polymerization of ethylene

This contribution describes the synthesis and characterization of a series of zirconium metallocenes derived from partially alkylated s-indacene. The complexes [Cp∗ZrCl2-s-Ic″H] 1, [Cp∗ZrCl2-s-Ic″H] 3 and [CpZrCl2-s-Ic″H] 4 (s-Ic′H=2,6-diethyl-4,8-dimethyl-1-hydro-s-indacene; s-Ic″H=2,6-dibutyl-4,8-dimethyl-1-hydro-s-indacene) were synthesized from the monolithiated salts of s-indacene (s-Ic′H or s-Ic″H) with one equivalent of C5R5ZrCl3 (R=H, CH3). All complexes here reported were characterized by means of 1H and 13C NMR, mass spectrometry, elemental analysis. Complexes [Cp∗ZrCl2-s-Ic′H] 1 and [CpZrCl2-s-Ic′H] 2 (previously reported by NMR analysis) were characterized by X-ray diffraction. In order to gain further knowledge about their catalytic behavior, the complexes were tested in the catalysis of ethylene polymerization showing a highest activity. Complex 4 presents the highest ethylene polymerization activity than complexes 1 and 2, and 3 under the same working conditions.

1,1-Olefin-bridged bis-(2-indenyl) metallocenes of titanium and zirconium.

Tetrasubstituted alkenes bearing geminal 2-indenyl substituents--9-[bis(1H-inden-2-yl)methylidene]-9H-fluorene (6), 2,2'-(2,2-diphenylethene-1,1-diyl)-bis(1H-indene) (7), and 2,2'-(2-propylpent-1-ene-1,1-diyl)-bis(1H-indene) (8) have been synthesized and metallated to form a new class of ansa titanium and zirconium metallocene complexes containing a single sp(2)-hybridized carbon bridge. The synthesis of the tetramethylated bis-indenyl Zr-analog is described. In addition, the 1,1-bis-indenyl ethylene is prepared and the Zr complex is modified by olefin metathesis. X-ray structure analyses reveal strained η(5) sandwich complexes with highly open metal centers. These complexes have proven active in the polymerization of ethylene and its copolymerization with 1-hexene.

Counter anion binding in the phenoxyimine, salan and metallocene olefin polymerization catalysts activated with perfluorophenylborate

Ion pair separation is a process that may influence the activity of homogeneous catalysts of olefin polymerization. We have studied the energy of separation for selected titanium and zirconium metallocene and post-metallocene catalytic ion pairs by means of DFT, dispersion-corrected DFT and Paired Interacting Orbitals method (PIO). Unusually weak cation–anion interactions in the bis(phenoxyimine) systems were attributed to strong electron-donating properties of the phenoxyimine ligands. Energy decomposition analysis (EDA) revealed that almost 70% of the counter ion binding energy results from electrostatic interactions. The PIO method made it possible to analyze the nature of the cation–anion binding and associate its strength with the total overlap population of PIOs.

Hard versus Soft Materials as Supports for Metallocene and Post‐Metallocene Catalysts

AbstractThe influence of organic supports on the polymerization behavior of post‐metallocene catalysts is studied and compared with similarly supported titanium and zirconium metallocenes. The effects of the immobilization, activation, and polymerization process were studied by video microscopy, laser confocal fluorescence microscopy, SEM, and TEM. A model for the polymerization process for a catalyst supported on latex particles was developed from the results obtained. Organic supports based on latex particles are easily adjustable for different catalysts due to the versatile functionalization of the surfaces and can be applied to different types of olefin polymerization catalysts. They can be considered as an alternative to SiO2 or MgCl2 supports.magnified image

Bis(2- N, N′-methylpiperazinoindenyl)zirconium dichloride. Crystal structure of bis(2- N, N′-methylpiperazinoindenyl)ZrCl 2

Synthesis of bis(2- N, N′-methylpiperazinoindenyl)zirconium dichloride is described. The solid state structure, based on single crystal X-ray diffraction, shows that the compound has a nearly C 2-symmetric conformation. This amino-substituted zirconium metallocene catalyst and methylaluminoxane as a cocatalyst yield polyethylene with narrow molecular weight distribution and very high activity.

Titanocene and Zirconocene Complexes containing Dendrimer-Substituted Cyclopentadienyl Ligands − Synthesis and Ethylene Polymerization

This paper describes the synthesis of a series of titanium and zirconium metallocenes bearing one or two first-generation silane dendritic wedges as bulky substituents at their cyclopentadienyl rings. Wedges (R2R′SiCH2CH2)3SiCl [R = R′ = Et (1); R = Ph, R′ = Me (2)] were prepared by hydrosilylation of chlorotrivinylsilane with R2R′SiH. They were reacted with K(C5H5) and, subsequently, with KH to give K[(R2R′SiCH2CH2)3Si(C5H4)] [R = R′ = Et (3); R = Ph, R′ = Me (4)]. The dendronized cyclopentadienides 3 and 4 were the starting materials for preparation of the mixed-ring titanocenes [{(R2R′SiCH2CH2)3SiC5H4}(C5R′′5)TiCl2] [R = R′ = Et, R′′ = H (5), R′′ = Me (6); R = Ph, R′ = Me, R′′ = H (7), R′′ = Me (8)] or the symmetrically substituted metallocenes [{(Ph2MeSiCH2CH2)3SiC5H4}2MCl2] [M = Ti (9), Zr (10)]. Cyclic voltammograms and catalytic behavior of all the new metallocenes in ethylene polymerization, using MAO as a cocatalyst, have been studied and compared to that of related non-dendritic complexes. Polyethylene polydispersities increase with the number of dendritic wedges in the catalyst, while activities decrease. Bimodal molecular weight distributions were clearly observed for the bis-dendritic titanocene 9. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis of Unbridged Bis(2-R-indenyl)zirconocenes Containing Functional Groups and Investigations in Propylene Polymerization

Five new indenyl zirconium metallocenes with 2-alkyl and 2-aryl substituents were synthesized and characterized. For the synthesis of the ligand the di-Grignard reagent 1,2-bis(magnesiomethyl)benzene dichloride was explored as a synthon to 2-substituted indenes. This procedure provides access to a variety of functionalized 2-indenylmetallocenes such as bis(2-ferrocenylindene)zirconium dichloride and bis(2-adamantylindenyl)zirconium dichloride. Crystallographic characterization of bis[2-(4-(dimethylamino)phenyl)indenyl] zirconium dichloride revealed an anti conformation with a coplanar orientation of the dimethylamino substituent to the aryl ring in the solid state. The polymerization behavior of all five zirconocene dichlorides in liquid propylene was studied in the presence of MAO at various temperatures, and the results were compared to those for the known catalyst system bis(2-phenylindenyl)zirconium dichloride/MAO (M1/MAO). The productivity of the 2-arylindene metallocenes in propylene polymerization ...

Determination of zirconium traces in polymers by ICP-IDMS - a powerful and fast method for routine testing of zirconium residues in polyolefins

Zirconium trace analyses play an important role for polyolefins produced by modern catalytic processes with zirconium metallocenes. A reliable and fast routine testing method by inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) was therefore developed, which allows the determination of zirconium in polymers down to the low ng/g level. With respect to its precision, accuracy, and time-consumption this method is suitable for routine testing of production processes. A spike solution, enriched in the stable isotope 91Zr, was prepared and used for the isotope dilution procedure, which has the advantage of being an internal “one point” calibration method. The polyolefin samples were dissolved by microwave assisted digestion with a mixture of concentrated HNO3/HF.