Gas-phase reactions of Fe(CH2O)+ and Fe(CH2S)+ with small alkanes: An experimental and theoretical study

Quan Chen, Huiping Chen, Sabre Kais, Ben S. Freiser

Research output: Contribution to journalArticle

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Abstract

The gas-phase reactions of Fe(CH2O)+ and Fe(CH2S)+ with a series of aliphatic alkanes were studied by Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Like bare Fe+, C-C insertion, particularly terminal C-C insertion, is predominant for the reactions of Fe(CH2O)+, while C-H insertion is preferred for Fe-(CH2S)+. About 90% of the Fe(CH2O)+ reaction products are formed by C-C insertion with small alkane loss. For Fe(CH2S)+, after initial C-H insertion, the proposed mechanism includes hydrogen transfer to sulfur, followed by migratory insertion of methylene into the metal-alkyl bond and formation of an activated H2S-Fe+- olefin complex, which dissociates by H2S elimination. The structures of the reaction products were probed by collision-induced dissociation, ion-molecule reactions, and use of labeled compounds yielding information about the reaction mechanism. Collision-induced dissociation and ligand displacement reactions yield the brackets D0(Fe+-C3H6) = 37 ± 2 kcal/mol < D0(Fe+- CH2S) < D0(Fe+-C6H6) = 49.6 ± 2.3 kcal/mol and D0(Fe+-CH2O) < D0(Fe+-C2H4) = 34 ± 2 kcal/mol. The optimized geometry of Fe(CH2O)+, obtained by density functional calculations, has C(2v) symmetry with a nearly undisturbed formaldehyde unit. The Fe+-CH2O bonding is found to be predominantly electrostatic with a calculated bond energy of 32.2 kcal/mol. However, the optimized Fe(CH2S)+ structure has C(s) symmetry with dative bonding between Fe+ and CH2S. D0(Fe+-CH2S) is calculated at 41.5 kcal/mol. The differences in geometry and chemical bonding between Fe(CH2O)+ and Fe(CH2S)+ are correlated with the different reaction pathways observed.

Original languageEnglish
Pages (from-to)12879-12888
Number of pages10
JournalJournal of the American Chemical Society
Volume119
Issue number52
DOIs
Publication statusPublished - 31 Dec 1997
Externally publishedYes

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Alkanes
Paraffins
Theoretical Models
Gases
Ions
Reaction products
Cyclotrons
Alkenes
Fourier Analysis
Static Electricity
Sulfur
Formaldehyde
Hydrogen
Cyclotron resonance
Mass Spectrometry
Geometry
Metals
Ligands
Olefins
Density functional theory

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Gas-phase reactions of Fe(CH2O)+ and Fe(CH2S)+ with small alkanes : An experimental and theoretical study. / Chen, Quan; Chen, Huiping; Kais, Sabre; Freiser, Ben S.

In: Journal of the American Chemical Society, Vol. 119, No. 52, 31.12.1997, p. 12879-12888.

Research output: Contribution to journalArticle

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title = "Gas-phase reactions of Fe(CH2O)+ and Fe(CH2S)+ with small alkanes: An experimental and theoretical study",
abstract = "The gas-phase reactions of Fe(CH2O)+ and Fe(CH2S)+ with a series of aliphatic alkanes were studied by Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Like bare Fe+, C-C insertion, particularly terminal C-C insertion, is predominant for the reactions of Fe(CH2O)+, while C-H insertion is preferred for Fe-(CH2S)+. About 90{\%} of the Fe(CH2O)+ reaction products are formed by C-C insertion with small alkane loss. For Fe(CH2S)+, after initial C-H insertion, the proposed mechanism includes hydrogen transfer to sulfur, followed by migratory insertion of methylene into the metal-alkyl bond and formation of an activated H2S-Fe+- olefin complex, which dissociates by H2S elimination. The structures of the reaction products were probed by collision-induced dissociation, ion-molecule reactions, and use of labeled compounds yielding information about the reaction mechanism. Collision-induced dissociation and ligand displacement reactions yield the brackets D0(Fe+-C3H6) = 37 ± 2 kcal/mol < D0(Fe+- CH2S) < D0(Fe+-C6H6) = 49.6 ± 2.3 kcal/mol and D0(Fe+-CH2O) < D0(Fe+-C2H4) = 34 ± 2 kcal/mol. The optimized geometry of Fe(CH2O)+, obtained by density functional calculations, has C(2v) symmetry with a nearly undisturbed formaldehyde unit. The Fe+-CH2O bonding is found to be predominantly electrostatic with a calculated bond energy of 32.2 kcal/mol. However, the optimized Fe(CH2S)+ structure has C(s) symmetry with dative bonding between Fe+ and CH2S. D0(Fe+-CH2S) is calculated at 41.5 kcal/mol. The differences in geometry and chemical bonding between Fe(CH2O)+ and Fe(CH2S)+ are correlated with the different reaction pathways observed.",
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N2 - The gas-phase reactions of Fe(CH2O)+ and Fe(CH2S)+ with a series of aliphatic alkanes were studied by Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Like bare Fe+, C-C insertion, particularly terminal C-C insertion, is predominant for the reactions of Fe(CH2O)+, while C-H insertion is preferred for Fe-(CH2S)+. About 90% of the Fe(CH2O)+ reaction products are formed by C-C insertion with small alkane loss. For Fe(CH2S)+, after initial C-H insertion, the proposed mechanism includes hydrogen transfer to sulfur, followed by migratory insertion of methylene into the metal-alkyl bond and formation of an activated H2S-Fe+- olefin complex, which dissociates by H2S elimination. The structures of the reaction products were probed by collision-induced dissociation, ion-molecule reactions, and use of labeled compounds yielding information about the reaction mechanism. Collision-induced dissociation and ligand displacement reactions yield the brackets D0(Fe+-C3H6) = 37 ± 2 kcal/mol < D0(Fe+- CH2S) < D0(Fe+-C6H6) = 49.6 ± 2.3 kcal/mol and D0(Fe+-CH2O) < D0(Fe+-C2H4) = 34 ± 2 kcal/mol. The optimized geometry of Fe(CH2O)+, obtained by density functional calculations, has C(2v) symmetry with a nearly undisturbed formaldehyde unit. The Fe+-CH2O bonding is found to be predominantly electrostatic with a calculated bond energy of 32.2 kcal/mol. However, the optimized Fe(CH2S)+ structure has C(s) symmetry with dative bonding between Fe+ and CH2S. D0(Fe+-CH2S) is calculated at 41.5 kcal/mol. The differences in geometry and chemical bonding between Fe(CH2O)+ and Fe(CH2S)+ are correlated with the different reaction pathways observed.

AB - The gas-phase reactions of Fe(CH2O)+ and Fe(CH2S)+ with a series of aliphatic alkanes were studied by Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Like bare Fe+, C-C insertion, particularly terminal C-C insertion, is predominant for the reactions of Fe(CH2O)+, while C-H insertion is preferred for Fe-(CH2S)+. About 90% of the Fe(CH2O)+ reaction products are formed by C-C insertion with small alkane loss. For Fe(CH2S)+, after initial C-H insertion, the proposed mechanism includes hydrogen transfer to sulfur, followed by migratory insertion of methylene into the metal-alkyl bond and formation of an activated H2S-Fe+- olefin complex, which dissociates by H2S elimination. The structures of the reaction products were probed by collision-induced dissociation, ion-molecule reactions, and use of labeled compounds yielding information about the reaction mechanism. Collision-induced dissociation and ligand displacement reactions yield the brackets D0(Fe+-C3H6) = 37 ± 2 kcal/mol < D0(Fe+- CH2S) < D0(Fe+-C6H6) = 49.6 ± 2.3 kcal/mol and D0(Fe+-CH2O) < D0(Fe+-C2H4) = 34 ± 2 kcal/mol. The optimized geometry of Fe(CH2O)+, obtained by density functional calculations, has C(2v) symmetry with a nearly undisturbed formaldehyde unit. The Fe+-CH2O bonding is found to be predominantly electrostatic with a calculated bond energy of 32.2 kcal/mol. However, the optimized Fe(CH2S)+ structure has C(s) symmetry with dative bonding between Fe+ and CH2S. D0(Fe+-CH2S) is calculated at 41.5 kcal/mol. The differences in geometry and chemical bonding between Fe(CH2O)+ and Fe(CH2S)+ are correlated with the different reaction pathways observed.

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