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Bertuleit, Axel; Könemann, Martin; Duda, Lothar; Erker, Gerhard; Fröhlich, Roland

doi:10.1023/a:1019172018940

Cited by 22 publications

(7 citation statements)

References 17 publications

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“…For the first part of this study we have used the (η 5 -C 5 H 4 −CMe 2 NMe 2 )CpZr bent-metallocene framework. The synthesis and some chemistry of its derivatives had been mentioned in a recent review by us but will briefly be outlined here for clarity. The C 5 H 4 −CMe 2 NMe 2 ligand system was prepared by a fulvene route.…”

Section: Resultsmentioning

confidence: 99%

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Evidence for α-Nitrogen Participation in the Internal C−H Activation Reaction at ((Dimethylamino)methyl)cyclopentadienyl-Derived Methylzirconocene Cations

et al. 1999

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Treatment of 6-(dimethylamino)-6-methylfulvene (1) with methyllithium followed by the reaction of the resulting [C 5 H 4 -CMe 2 NMe 2 ]Li reagent with CpZrCl 3 gave the complex [(η 5 -C 5 H 4 -CMe 2 NMe 2 )CpZrCl 2 ] (2). Its treatment with 2 molar equiv of methyllithium furnished [(η 5 -C 5 H 4 -CMe 2 NMe 2 )CpZr(CH 3 ) 2 ] (3). Complex 3 reacted with B(C 6 F 5 ) 3 by methyl group transfer. The in situ [Zr] + -CH 3 cation system generated in this manner proved to be unstable under the reaction conditions and instantaneously eliminated methane with formation of 4. In the course of this reaction a N-CH 3 hydrogen atom was abstracted. Complex 4 was stabilized by the addition of 1 equiv of the alkyl isocyanide RNtC (R ) CMe 3 , n-C 4 H 9 , -CMe 2 -CH 2 CMe 3 ) to yield the respective adducts 5. The complex [(η 5 :η 2 (C,N)-C 5 H 4 -CMe 2 N(dCH 2 )-CH 3 )CpZr(κC-CtN-CMe 3 )] + [CH 3 B(C 6 F 5 ) 3 ] -(5a) was characterized by an X-ray crystal structure analysis. It exhibits an η 2 -coordination of the pendant formaldiminium moiety to zirconium (d(Zr-N) ) 2.318(7) Å, d(Zr-C) ) 2.272(7) Å). The (η 2 -R 2 NCH 2 )Zr moiety shows a characteristic 15 N NMR chemical shift (δ -376 ppm), deshielded by ca. ∆δ ≈ -40 ppm relative to the 15 NMe 2 NMR resonance found for 3. Complex 4 reacts with butadiene or isoprene by insertion into the Zr-CH 2 bond of the (η 2 -formaldiminium)Zr moiety to form the metallacyclic (π-allyl)metallocene complexes 6a,b. The X-ray crystal structure analysis of 6b shows a close Zr-N contact at 2.491(4) Å. A corresponding 15 N NMR feature was found at δ -357 ppm. The complex [(η 5 -C 5 H 4 -CMe 2 NMe 2 ) 2 Zr(CH 3 ) 2 ] reacts analogously: upon treatment with B(C 6 F 5 ) 3 in a 1:1 ratio, CH 3 is transferred from zirconium to boron, and 1 equiv of methane is liberated to give complex 8 ( 15 N NMR signals at δ -357 and -372 ppm). Complex 8 was also characterized by X-ray diffraction. It shows coordination of both nitrogen atoms to zirconium: i.e., the presence of a (η 2 -R 2 NCH 2 )Zr + three-membered-ring system, formed by C-H activation, and a κN-coordinated intact pendant -CMe 2 -NMe 2 group. The latter is displaced upon the addition of tert-butyl isocyanide to yield the (κC-isonitrile)(η 2formaldiminium)metallocene cation complex 9.

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Section: Resultsmentioning

confidence: 99%

“…For additional general information see ref . 6-(Dimethylamino)-6-methylfulvene ( 1 ) was prepared according to the procedure of Hafner et al Complexes 2 and 3 (including their structures) were briefly mentioned by us previously in a review . Some of the data for these compounds are listed below for comparison.…”

Section: Methodsmentioning

confidence: 99%

Evidence for α-Nitrogen Participation in the Internal C−H Activation Reaction at ((Dimethylamino)methyl)cyclopentadienyl-Derived Methylzirconocene Cations

et al. 1999

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“…[4] ) The preparation of 3 was described by us previously. [4] Complex 1 [5] and B(C 6 F 5 ) 3 [6] were prepared as described in the literature.…”

Section: Methodsmentioning

confidence: 99%

“…[3] However, they can also undergo CϪH activation reactions if suitable reagents are brought in the vicinity of the [Zr] ϩ ϪCH 3 moiety. [4] Such behavior is observed when the amino-functionalized metallocene (CpϪCMe 2 NMe 2 )CpZr(CH 3 ) 2 (1) [5] is treated with the alkyl abstractor B(C 6 F 5 ) 3 (Scheme 1). [6] The alkylzirconocene cation 2 which is generated in situ, is not stable under the reaction conditions but rapidly reacts further by proton abstraction from the pendant NϪCH 3 group to form 3 with methane evolution.…”

Section: Introductionmentioning

confidence: 99%

Addition and Coupling Reactions of Zirconocene Cation Complexes that Contain a Pendant η2-Formaldiminium Side Chain

Pflug

Erker

Kehr

et al. 2000

Eur. J. Inorg. Chem.

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“…Compounds 2 were synthesized as previously described by us . The compounds 2A and 2B were prepared by different variants of fulvene routes . Treatment of 6- tert -butylpentafulvene ( 3 ) with lithium p -methoxyanilide ( 4A ) gave the addition product ( 5 ), which represents a functionalized lithium cyclopentadienide.…”

Section: Discussionmentioning

confidence: 99%

Remarkable Dichotomy of Oligomeric Chain Structures of Dilithium(amidoalkyl-cyclopentadienide) Systems Li₂[C₅H₄-CHR-NAr]

et al. 2007

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The dilithium compounds Li2[Cp-CHR1-NAr1] 2A (R1 = tert-butyl, Ar1 = p-anisyl) and Li2[Cp-CHR2-NAr2] 2B (R2 = methyl, Ar2 = o-anisyl) were synthesized by means of fulvene routes as previously described. Single crystals were obtained from THF/pentane. Both systems feature oligomeric chain structures in the solid state. Compound 2A exhibits a head-to-tail arrangement of monomeric units with recurring chain-constructing (amide)N-Li-(η5-Cp) units whereas 2B favors a head-to-head type structure with alternating η5-Cp-Li-η5-Cp lithiocene and bis(N,O-chelate)Li building blocks. In each case the remaining Li+ ions are coordinated toward the periphery of the main chain as Li(THF)2 (2A) or Li(THF) (2B) solvates.

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Cited by 22 publications

References 17 publications

Evidence for α-Nitrogen Participation in the Internal C−H Activation Reaction at ((Dimethylamino)methyl)cyclopentadienyl-Derived Methylzirconocene Cations

Evidence for α-Nitrogen Participation in the Internal C−H Activation Reaction at ((Dimethylamino)methyl)cyclopentadienyl-Derived Methylzirconocene Cations

Addition and Coupling Reactions of Zirconocene Cation Complexes that Contain a Pendant η2-Formaldiminium Side Chain

Remarkable Dichotomy of Oligomeric Chain Structures of Dilithium(amidoalkyl-cyclopentadienide) Systems Li₂[C₅H₄-CHR-NAr]

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Untitled

Cited by 22 publications

References 17 publications

Evidence for α-Nitrogen Participation in the Internal C−H Activation Reaction at ((Dimethylamino)methyl)cyclopentadienyl-Derived Methylzirconocene Cations

Evidence for α-Nitrogen Participation in the Internal C−H Activation Reaction at ((Dimethylamino)methyl)cyclopentadienyl-Derived Methylzirconocene Cations

Addition and Coupling Reactions of Zirconocene Cation Complexes that Contain a Pendant η2-Formaldiminium Side Chain

Remarkable Dichotomy of Oligomeric Chain Structures of Dilithium(amidoalkyl-cyclopentadienide) Systems Li2[C5H4-CHR-NAr]

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Remarkable Dichotomy of Oligomeric Chain Structures of Dilithium(amidoalkyl-cyclopentadienide) Systems Li₂[C₅H₄-CHR-NAr]