Neutral and cationic trimethylsilylmethyl complexes of the rare earth metals supported by a crown ether: synthesis and structural characterization

Arndt, Stefan; Zeimentz, Peter M.; Spaniol, Thomas P.; Okuda, Jun; Honda, Masahiro; Tatsumi, Kazuyuki

doi:10.1039/b305964b

Cited by 55 publications

(61 citation statements)

References 24 publications

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“…[63] In contrast to the lutetium complex, the isolated scandium and yttrium complexes do not contain a THF ligand. For À is a rare example of a complex with direct coordination of 18-crown-6 to lutetium.…”

Section: Dedicated Cluster Reviewsmentioning

confidence: 97%

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

2005

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This contribution is dedicated to Dick Schrock on the occasion of his 60th birthday.Abstract: Cationic alkyl complexes of the rare-earth metals [LnR m ; L ¼ Lewis base) were virtually unknown species until recently. Because of their increased Lewis acidity/electrophilicity they should have considerable potential as homogeneous catalysts in olefin polymerization and in organic transformations. They can be generated by treating the neutral rare-earth metal precursors containing at least two alkyl groups R with suitable Lewis or Brønsted acids in the presence of weakly coordinating anions. Not only monocationic but also dicationic alkyl derivatives have been shown to be accessible. In the context of modeling homogeneous ethylene polymerization using a mixture consisting of LnR 3 /AlR 3 /[NMe 2 HPh][B(C 6 F 5 ) 4 ], such dications were discovered. Some thermally robust examples of mono-and dicationic alkyl complexes have been structurally characterized as solvent-separated ion pairs. Neutral and monoanionic macrocycles such as crown ethers or aza-crown ethers as well as amidinato, b-diketiminato, and substituted cyclopentadienyl ligands are suitable ancillary ligands to stabilize the cationic alkyl fragments.

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Section: Dedicated Cluster Reviewsmentioning

confidence: 97%

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

2005

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“…[1][2][3][4][5][6][7][8][9][10] A number of cationic alkyl-rare-earth-metal complexes supported by various ancillary ligands such as deprotonated aza crowns, [2] benzamidinates, [3] b-diketiminates, [4] anilido imines, [5] amidefunctionalized triazacyclononanes, [6] phosphides, [7] cyclopentadienyls, [8] and crown ethers [9] have been synthesized and their reactivity has been studied. Despite these extensive efforts, however, the olefin-polymerization chemistry of the cationic alkyl-rare-earth-metal complexes is still limited solely to that of ethylene, [2][3][4][5][6][7][8][9][10] whereas the development of active rare-earth-metal catalysts for the efficient polymerization/copolymerization of higher olefins has remained a challenge.The copolymer of ethylene with a cyclic olefin such as norbornene (COC) is one of the most important highperformance polymer materials with many desirable properties. Since Kaminsky et al first described the copolymerization of ethylene (E) with norbornene (NB) by using zirconocene-based catalysts in 1991, [11] extensive studies have been carried out in this area.…”

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confidence: 99%

Alternating Ethylene–Norbornene Copolymerization Catalyzed by Cationic Half‐Sandwich Scandium Complexes

Baldamus²,

Hou³

2005

Angew Chem Int Ed

200

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Cationic alkyl-rare-earth-metal complexes (i.e., Group 3 and the lanthanides) have recently attracted much interest as homogeneous polymerization catalysts. [1][2][3][4][5][6][7][8][9][10] A number of cationic alkyl-rare-earth-metal complexes supported by various ancillary ligands such as deprotonated aza crowns, [2] benzamidinates, [3] b-diketiminates, [4] anilido imines, [5] amidefunctionalized triazacyclononanes, [6] phosphides, [7] cyclopentadienyls, [8] and crown ethers [9] have been synthesized and their reactivity has been studied. Despite these extensive efforts, however, the olefin-polymerization chemistry of the cationic alkyl-rare-earth-metal complexes is still limited solely to that of ethylene, [2][3][4][5][6][7][8][9][10] whereas the development of active rare-earth-metal catalysts for the efficient polymerization/copolymerization of higher olefins has remained a challenge.The copolymer of ethylene with a cyclic olefin such as norbornene (COC) is one of the most important highperformance polymer materials with many desirable properties. Since Kaminsky et al. first described the copolymerization of ethylene (E) with norbornene (NB) by using zirconocene-based catalysts in 1991, [11] extensive studies have been carried out in this area. Most of the catalysts reported so far are complexes based on transition metals such as those of Group 4 and Group 10, [12] whereas no rare-earthmetal complex has been previously used for the copolymerization of ethylene with norbornene. [13] Herein we report an excellent cationic half-sandwich scandium catalyst for the copolymerization of ethylene with norbornene. This catalyst not only represents the first example of a rare-earth-metal catalyst for ethylene-norbornene copolymerization, but it also shows several unique characteristics, such as extremely high activity for the alternating ethylene-norbornene copolymerization and unprecedented formation of novel poly(ethylene-alt-norbornene)-bpolyethylene block copolymers.

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“…Unfortunately its crystal structure could not be refined satisfactorily because of disorder of the coordinated THF and DME molecules [12]. It appears that in contrast to the direct synthesis of Lu(CH 2 SiMe 3 ) 3 (12-crown-4) from 2 and 12-crown-4, recently described [13], substitution of only one THF by DME has occured. A further displacement of coordinated THF by DME could not be accomplished.…”

Section: Resultsmentioning

confidence: 99%

Studies on the Thermolysis of Ether-Stabilized Lu(CH₂SiMe₃)₃. Molecular Structure of Lu(CH₂SiMe₃)₃(THF)(diglyme)

Rufanov

Freckmann

Kroth

et al. 2005

Zeitschrift Für Naturforschung B

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Lu(CH2SiMe3)3(THF)2 (2) decomposes slowly at room temperature with formation of Me4Si. In order to understand the mechanism of this elimination process, Lu(CH2SiMe3)3([D8]-THF)2 (1), Lu(CH2SiMe3)3(THF)(DME) (3), and Lu(CH2SiMe3)3(THF)(diglyme) (4) were prepared. The results of 1H NMR spectroscopic studies of the decomposition in solution exclude an α- as well as a β -H elimination mechanism and point towards a γ -H elimination. The molecular structure of 4 has been determined by single crystal X-ray diffraction.

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Neutral and cationic trimethylsilylmethyl complexes of the rare earth metals supported by a crown ether: synthesis and structural characterization

Cited by 55 publications

References 24 publications

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

Alternating Ethylene–Norbornene Copolymerization Catalyzed by Cationic Half‐Sandwich Scandium Complexes

Studies on the Thermolysis of Ether-Stabilized Lu(CH₂SiMe₃)₃. Molecular Structure of Lu(CH₂SiMe₃)₃(THF)(diglyme)

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Neutral and cationic trimethylsilylmethyl complexes of the rare earth metals supported by a crown ether: synthesis and structural characterization

Cited by 55 publications

References 24 publications

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

Alternating Ethylene–Norbornene Copolymerization Catalyzed by Cationic Half‐Sandwich Scandium Complexes

Studies on the Thermolysis of Ether-Stabilized Lu(CH2SiMe3)3. Molecular Structure of Lu(CH2SiMe3)3(THF)(diglyme)

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Studies on the Thermolysis of Ether-Stabilized Lu(CH₂SiMe₃)₃. Molecular Structure of Lu(CH₂SiMe₃)₃(THF)(diglyme)