Gas-Phase Reactions of Fe(CH2O)+ and Fe(CH2S)+ with Small Alkanes: An Experimental and Theoretical Study
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- 作者：Quan Chen ; Huiping Chen ; Sabre Kais ; and Ben S. Freiser
- 刊名：Journal of the American Chemical Society
- 出版年：1997
- 出版时间：December 31, 1997
- 年：1997
- 卷：119
- 期：52
- 页码：12879 - 12888
- 全文大小：414K
- 年卷期：v.119,no.52(December 31, 1997)
- ISSN：1520-5126
文摘
The gas-phase reactions ofFe(CH2O)+ andFe(CH2S)+ with a series of aliphaticalkanes were studied byFourier transform ion cyclotron resonance (FTICR) mass spectrometry.Like bare Fe+, C-C insertion,particularlyterminal C-C insertion, is predominant for the reactions ofFe(CH2O)+, while C-H insertion ispreferred for Fe(CH2S)+. About 90% of theFe(CH2O)+ reaction products are formedby C-C insertion with small alkane loss.For Fe(CH2S)+, after initial C-Hinsertion, the proposed mechanism includes hydrogen transfer to sulfur,followedby migratory insertion of methylene into the metal-alkyl bond andformation of an activatedH2S-Fe+-olefincomplex, which dissociates by H2S elimination. Thestructures of the reaction products were probed bycollision-induced dissociation, ion-molecule reactions, and use of labeledcompounds, yielding information about the reactionmechanism. Collision-induced dissociation and ligand displacementreactions yield the bracketsD0(Fe+-C3H6)=37 ± 2 kcal/mol <D0(Fe+-CH2S) <D0(Fe+-C6H6)= 49.6 ± 2.3 kcal/mol andD0(Fe+-CH2O) <D0(Fe+-C2H4)= 34 ± 2 kcal/mol. The optimized geometry ofFe(CH2O)+, obtained by densityfunctional calculations, hasC2vsymmetry with a nearly undisturbed formaldehyde unit. TheFe+-CH2O bonding is found to bepredominantlyelectrostatic with a calculated bond energy of 32.2 kcal/mol.However, the optimized Fe(CH2S)+structure has Cssymmetry with dative bonding between Fe+ andCH2S.D0(Fe+-CH2S)is calculated at 41.5 kcal/mol. The differencesin geometry and chemical bonding betweenFe(CH2O)+ andFe(CH2S)+ are correlated with thedifferent reactionpathways observed.