Stereochemical effect in mass spectrometry of transition metal π‐complexes

Nekrasov, Yurii S.; Zagorevskii, V.

doi:10.1002/oms.1210260903

Cited by 15 publications

(4 citation statements)

References 27 publications

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“…Despite the huge importance of transition-metal catalysts in asymmetric synthesis, there so far exist only very few reports about stereoselective reactions of gaseous metal ions in general and even less about such effects in the bond activation of alkanes. , In this respect, the late Ben S. Freiser initiated a fascinating research project centered about the use of metal-mediated dehydrogenation reactions in a mass spectrometer for the analysis of the diastereospecifity of hydrogenation catalysts . With respect to this specific analytical application, the use of early transition metals is of advantage because the dehydrogenations occur fast, completely, and with minimal H/D scrambling.…”

Section: Regioselective Gas-phase Activation Of Alkanesmentioning

confidence: 99%

Selective Activation of Alkanes by Gas-Phase Metal Ions

2009

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Section: Regioselective Gas-phase Activation Of Alkanesmentioning

confidence: 99%

Selective Activation of Alkanes by Gas-Phase Metal Ions

2009

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“…40 This process occurs in most ferrocenylalkyl derivatives CpFeC 5 H 4 CHRX containing a nucleophilic moiety X = OH, NR 2 , halogen, etc. 39,41 In our case, the main fragmentation pathway is elimination of the heterocycle with the heterolytic cleavage of the C-N bond and the formation of a fragment ion [MCHPh] + (m/z 275) and ions Nu + . Analysis of the mass spectra of the obtained compounds indicates a low strength of the С-N bond, which manifests itself in a high abundance of the ions [MCHPh] + (up to 100%) and the presence of fragment ions [СрFeNu] + and [Nu] + , resulting from the cleavage of this bond.…”

Section: Methodsmentioning

confidence: 85%

The nature of ferrocenylalkylating agent in the acid-catalyzed reactions with ferrocenyl(phenyl)methanol

et al. 2021

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The reaction of α-ferrocenyl(phenyl)methanol with various azoles under the phase transfer catalysis conditions aff orded a series of ferrocenyl(alkyl)azoles in high yields. The structure of ferrocenyl(phenylmethyl)-3-trifl uoromethyl-5-(2-thienyl)pyrazole was established by X-ray diff raction. The formation of a biradical cation from the intermediately formed ferrocenyl(phenyl)carbenium ion, FcСН(Ph) + , was detected by ESR spin trap technique. Despite the demonstrated possibility of the formation of biradical cations, no products characteristic of the radical reaction pathway were found, which may serve as an indirect evidence that the reaction follows the S N 1 -mechanism.

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“…[5][6][7] Another fragmentation path associated with the cleav age of the carbon-heterocycle bond substantially depends on the nature of the substituent R. If R = H or Ph, the process involves ordinary cleavage of this bond with elimi nation of the azolyl radical. In the case of alkyl substi tuted derivatives, this process is accompanied by migra tion of the hydrogen atom to the heterocycle followed by elimination of the azole molecule to give ions of the cor responding vinylferrocenes and AzH + (see Scheme 1).…”

Section: Resultsmentioning

confidence: 99%

Reactivity of ferrocenylalkylazoles under conditions of dissociative ionization

et al. 2005

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Electron ionization mass spectra of biologically active ferrocenylalkylazoles CpFeC 5 H 4 CH(R)Az (R = H, Me, Et, Pr, or Ph; AzH is pyrazole, imidazole, indazole, benzoimidazole, benzotriazole, adenine, or their derivatives) were studied. The nature of the heterocyclic fragment (its ionization energy) is the main factor determining the reactivity of these compounds under conditions of dissociative electron ionization.Pronounced antitumor activity of ferrocenylalkylazoles combined with low toxicity allows these compounds to be considered as precursors for the design of highly efficient drugs for chemotherapy of tumor diseases. 1-4 In this con nection, studies of the physicochemical properties and reactivities of these compounds are of considerable im portance. In the present study, we examined the behavior of ferrocenylalkylazoles 1-23 with the composition CpFeC 5 H 4 CH(R)Az (R = H, Me, Et, Pr, or Ph; AzH is pyrazole, imidazole, indazole, benzoimidazole, benzo triazole, adenine, or their derivatives) under conditions of dissociative electron ionization (Scheme 1) by mass spectrometry. Our interest here is with both the analytical and research aspects of this problem. The former consists of the development of procedures for the determination of the compositions, structures, and purities of this class of biologically active compounds. The latter consists of the study of the reactivities of such molecules and their ions in the gas phase. Results and DiscussionThe mass spectra of all the compounds under study have intense peaks of molecular ions, whose fragmenta tion follows several paths. The ordinary cleavage of the metal-ligand bond with elimination of substituted and unsubstituted cyclopentadienyl ligands up to the forma tion of the free iron cation 5,6 is common to these com pounds, as well as to all ferrocene derivatives.The characteristic feature of the behavior of all ferrocenylalkylazoles under conditions of dissociative electron ionization is that they undergo a rearrangement accompanied by migration of the heterocyclic fragment Scheme 1 R = H (1-9), Me (10-17), Et (18-20), Pr (21, 22), Ph (23)to the iron atom giving rise to the CpFeAz + and FeAz + ions containing the metal-azole bond (see Scheme 1).

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Stereochemical effect in mass spectrometry of transition metal π‐complexes

Cited by 15 publications

References 27 publications

Selective Activation of Alkanes by Gas-Phase Metal Ions

Selective Activation of Alkanes by Gas-Phase Metal Ions

The nature of ferrocenylalkylating agent in the acid-catalyzed reactions with ferrocenyl(phenyl)methanol

Reactivity of ferrocenylalkylazoles under conditions of dissociative ionization

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