Formation of Dinuclear Titanium and Zirconium Complexes by Olefin Metathesis—Catalytic Preparation of Organometallic Catalyst Systems

Cano, Jesús; Hüerländer, Doris; Hill, Michael S.; Kehr, Gerald; Erker, Gerhard; Fröhlich, Roland

doi:10.1002/chem.200304789

Cited by 59 publications

(32 citation statements)

References 89 publications

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“…However, carbon-carbon coupling reactions at the intact group 4 bent metallocene frameworks were close to nonexistent before our work (13)(14)(15). Meanwhile, a few leading examples have emerged from the literature, using, e.g., olefin-metathesis (16)(17)(18)(19) or even a variant of the Mannich reaction (20)(21)(22) for carrying out carbon-carbon coupling reactions at the reactive group 4 bent metallocene frameworks.…”

mentioning

confidence: 80%

Ansa-metallocene polymerization catalysts derived from [2+2]cycloaddition reactions of bis(1-methylethenyl-cyclopentadienyl)zirconium systems

Paradies

Kehr

Fröhlich

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Bis(1-methylethenyl-cyclopentadienyl)zirconium dichloride (7a) was prepared by a fulvene route. Photolysis at 0°C with Pyrexfiltered UV light resulted in a rapid and complete intramolecular [2؉2]cycloaddition reaction to yield the corresponding cyclobutylene-bridged ansa-zirconocene dichloride isomer (8a). This is one of the rare examples of an organic functional group chemistry that leads to carbon-carbon coupling at the framework of an intact sensitive group 4 bent metallocene complex. More sterically hindered open metallocenes that bear bulky isopropyl or tert-butyl substituents at their Cp rings in addition to the active 1-methylethenyl functional group undergo the photochemical ansa-metallocene ring closure reaction equally facile. The metallocene systems used and obtained in this study have served as transition metal components for the generation of active metallocene propene polymerization catalysts.photochemistry ͉ topochemical reaction M etallocene catalysis has become of great significance in olefin polymerization, especially for polyethylene, stereospecific polypropylene formation, and the production of some copolymers. The ansa-metallocenes of the group 4 metals and related systems play an essential role in this important development (1-3). Various methods have been devised and applied to construct such bent metallocene frameworks that feature a short carbon-or heteroatom-containing bridge between their substituted cyclopentadienyl, indenyl, or fluorenyl ligands. Because of the sensitive character of the organometallic group 4 metal complexes, ligand construction and variation is usually carried out at the free ligand stage before the final transmetallation step to the transition metal in the practical preparative sequences. This is a serious synthetic limitation. It would be highly desirable to have an organic functional group chemistry developed for framework variation at the actual metallocene stage. Previously, some addition reactions to metallocene frameworks had been reported, such as catalytic hydrogenation (4), hydrosilylation (5), hydroboration (6-9), or borylation (refs. 10, 11 and references therein, and 12). However, carbon-carbon coupling reactions at the intact group 4 bent metallocene frameworks were close to nonexistent before our work (13-15). Meanwhile, a few leading examples have emerged from the literature, using, e.g., olefin-metathesis (16-19) or even a variant of the Mannich reaction (20-22) for carrying out carbon-carbon coupling reactions at the reactive group 4 bent metallocene frameworks.Intramolecular photochemical [2ϩ2]cycloaddition reactions may become of a prime importance in this development. We had previously observed that bis(alkenyl-Cp)ZrCl 2 complexes such as, e.g., meso-1 underwent ansa-metallocene formation to yield meso-2 by intramolecular [2ϩ2]cycloaddition when irradiated with UV light. However, this specific reaction was not synthetically useful for a clean ansa-metallocene catalyst development because of its reversibility under the photochemical conditions t...

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mentioning

confidence: 80%

Ansa-metallocene polymerization catalysts derived from [2+2]cycloaddition reactions of bis(1-methylethenyl-cyclopentadienyl)zirconium systems

Paradies

Kehr

Fröhlich

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…The butenyl moiety bond distances are C(9)-C(10) 151.9(4); C(10)-C(11) 149.4(5); C(11)-C(12) 128.0(5) pm. The distance C(11)-C(12) is typical for terminal C-C double bonds [73,74,[101][102][103] and the angle C(10)-C(11)-C(12), 126.4(4)°, confirms the sp 2 hybridization of C (12). Selected bond lengths and angles for 13 are summarized in Table 3.…”

Section: Structural Studiesmentioning

confidence: 92%

Cytotoxic studies of substituted titanocene and ansa-titanocene anticancer drugs

Gómez‐Ruiz

Kaluđerović²,

Prashar

et al. 2008

Journal of Inorganic Biochemistry

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“…Treatment of 7 with a more reactive second generation Grubbs catalyst (5b), that contains an dihydroimidazol-2-ylidene ligand, selectively gave the thermodynamically favoured trans-product 8b in good yield (see Scheme 3 and Fig. 2) [8]. Complex 8b was characterized by X-ray diffraction.…”

Section: Olefin Metathesismentioning

confidence: 99%

“…Related Group 4 bent metallocene complexes that contained a pendant allyl group at a Cp-ring also gave the respective dimetallic butendiyl-linked olefin metathesis coupling products when treated with the 5a or 5b catalysts. Some of these products gave rather active homogeneous ZieglerNatta catalysts upon activation with a large excess of methylalumoxane [1,8] …”

Section: Olefin Metathesismentioning

confidence: 99%

Developing some functional group chemistry at the Group 4 bent metallocene frameworks

Erker¹,

Kehr²,

Fröhlich³

2004

Journal of Organometallic Chemistry

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Formation of Dinuclear Titanium and Zirconium Complexes by Olefin Metathesis—Catalytic Preparation of Organometallic Catalyst Systems

Cited by 59 publications

References 89 publications

Ansa-metallocene polymerization catalysts derived from [2+2]cycloaddition reactions of bis(1-methylethenyl-cyclopentadienyl)zirconium systems

Ansa-metallocene polymerization catalysts derived from [2+2]cycloaddition reactions of bis(1-methylethenyl-cyclopentadienyl)zirconium systems

Cytotoxic studies of substituted titanocene and ansa-titanocene anticancer drugs

Developing some functional group chemistry at the Group 4 bent metallocene frameworks

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