σ‐Dicarbonylcyclopentadienyliron Derivatives of Cyclopropenes and Cyclopropenylium Salts

Gompper, Rudolf; Bartmann, Ekkehard

doi:10.1002/anie.197804561

Cited by 46 publications

(17 citation statements)

References 6 publications

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“…The first isolated σ-bound cyclopropenylium-metal complexes were reported in 1978 in consecutive articles by Gompper and Bartmann (1978) and by Weiss and Priesner (1978) following two different approaches.…”

Section: σ-Complexesmentioning

confidence: 99%

“…While the formation of NaX (X = cyclopropenium counter ions) is a strong driving force for this reaction, the neutral compound 2 is highly strained and reactive from loss of aromaticity. Stability from aromaticity was easily restored by abstraction of the R 2 group (e.g., Ph, He, H, Cl) with appropriate abstracting agent E (e.g., HCl, I 2 , [(Ph) 3 C + ][BF 4 - ]), resulting in the σ-bound cyclopropenylium ion complexes 3 (Gompper and Bartmann, 1978).…”

Section: σ-Complexesmentioning

confidence: 99%

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Molecular Orbital Insights of Transition Metal-Stabilized Carbocations

2019

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Transition metal-stabilized carbocations are characterized by synthetically valuable interactions, yet, to date there are no comprehensive reports of the many bonding modes that can exist between a metal and carbocation. This review summarizes developments in these complexes to provide a clear picture of their properties and reactivities. In order to strategically exploit them, we propose this summary of the different bonding modes for transition metal-carbocation complexes. These models will help chemists understand the orbital interactions involved in these compounds so that they can approach their synthetic goals most effectively. Multiple transition metals and carbocations will be discussed.

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Section: σ-Complexesmentioning

confidence: 99%

Section: σ-Complexesmentioning

confidence: 99%

Molecular Orbital Insights of Transition Metal-Stabilized Carbocations

2019

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“…It has also been shown that this compound, generated in situ, effectively transfers the cyclopropenylidene moiety 4 to a number of substrates, including transition metals and main group fragments. [8,9,11,12] Weiss proposed the formation of the carbene lithium adduct 3 (X = ClO 4 ), rather than that of the free carbene 4, based primarily on the observation that no LiClO 4 precipitated from the reaction mixture.…”

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confidence: 99%

Isolation of Cyclopropenylidene–Lithium Adducts: The Weiss–Yoshida Reagent

et al. 2006

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A lithium-halogen exchange reaction occurs when the chloro[bis(diisopropylamino)] cyclopropenium tetrafluoroborate salt 1 (X = BF 4 ) is treated with n-butyllithium. The resulting cyclopropenylidene-lithium adduct 3 has been isolated in 45% yield. In the solid state, this compound exists as a polymeric chain with an overall stoichiometry of two LiBF 4 per carbene ligand. Addition of 12-crown-4-ether does not liberate the carbene from the lithium cation, but affords a monomeric tertiary complex (60% yield) that includes the crown ether. Moreover, complex 3 can also be synthesized by depro tonation of the bis(diisopropylamino)cyclopropenium tetrafluoroborate salt 2 (X = BF 4 ) with n-butyllithium, whereas using potassium bis(trimethylsilyl)amide the free cyclopropenylidene was isolated in 53% yield. These results as whole seem to demonstrate that only certain counteranions allow for the isolation of cyclopropenylidene-lithium adducts, and only bases not containing lithium allow for the isolation of the free cyclopropenylidene. The former and the latter presumably prevented Weiss and Yoshida from isolating what would have been the first example of a stable carbene-lithium adduct and a free carbene, respectively. KeywordsCarbenes; cyclopropenylidene; Li; Complex In the 1950s, Breslow[1] and Wanzlick [2] realized that the stability of a carbene could be dramatically enhanced by the presence of amino substituents, but they were unable to isolate a "monomeric" carbene.[3] It was only in 1991, three years after the isolation of a (phosphino) (silyl)carbene,[4] that a bottle-able diamino carbene, namely an imidazol-2-ylidene, was prepared.[5] Even more strikingly, in a paper entitled "1,2,3,4-Tetraphenylimidazol-2-ylidene: The Realization of Wanzlick's Dream", Arduengo [6] reported that a modification of the experimental procedure published by Wanzlick's group makes it possible to isolate one of the exact same carbenes postulated in 1970. [7] Wanzlick was not the only one to nearly isolate the first stable carbene. Indeed, in the 1970s, Yoshida [8] and Weiss [9] attempted independently the preparation of the bis (diisopropylamino)cyclopropenylidene 4 (Fig. 1). Recently, we isolated the exact same carbene (4) after deprotonation of cyclopropenium salt 2 (X = BPh 4 ) with potassium bis(trimethylsilyl) amide.[10] Among the routes used by Yoshida and Weiss were lithium-halogen exchange from 1 (X = ClO 4 )[9a] and the deprotonation of 2 (X = ClO 4 ),[8a,b] both with n-BuLi. However, they were not able to isolate the resulting product. Initially, Yoshida claimed the successful synthesis of the free cyclopropenylidene 4,[8a] but several years later he[8b-e] and Weiss ** We are grateful to the NIH (R01 GM 68825) and Rhodia for financial support of this work, and to the JSPS for a Fellowship to Y. I.

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“…Unlike 3, however, the cyclopropenylidene units in these complexes are substituted by phenyl or electrondonating groups. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] [Ru(C)(H 2 IMes)(PCy 3 )Cl 2 ] (4; H 2 IMes = 4,5-dihydro-1,3-bis(mesityl)imidazol-2-ylidene) reacts similarly with DMAD, but the reaction is not clean since the product reacts further with DMAD before all of 4 has been consumed. However, 4 reacts more cleanly with HCCCO 2 Me (see the Supporting Information).…”

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confidence: 99%

Carbon–Carbon Bond Formation at a Neutral Terminal Carbido Ligand: Generation of Cyclopropenylidene and Vinylidene Complexes

et al. 2006

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A C1 source, the carbido complex [Ru(C)(PCy3)2Cl2] (1) adds cleanly to dimethylacetylene dicarboxylate (DMAD), affording the cyclopropenylidene complex 2 (red O, green Cl, yellow P, gray C). This product is surprising given the instability of its trans‐cyclopropylidene analogue. HX reagents effect 1,1‐addition and ring opening, forming vinylidene complexes such as 3 which catalyze the ring‐opening metathesis polymerization of norbornene.

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σ‐Dicarbonylcyclopentadienyliron Derivatives of Cyclopropenes and Cyclopropenylium Salts

Cited by 46 publications

References 6 publications

Molecular Orbital Insights of Transition Metal-Stabilized Carbocations

Molecular Orbital Insights of Transition Metal-Stabilized Carbocations

Isolation of Cyclopropenylidene–Lithium Adducts: The Weiss–Yoshida Reagent

Carbon–Carbon Bond Formation at a Neutral Terminal Carbido Ligand: Generation of Cyclopropenylidene and Vinylidene Complexes

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