Pseudo-tetrahedral semi-sandwich cycloruthenated compounds: 1H NMR data and DFT-calculations about the racemisation process of the ruthenium atom - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Comptes Rendus. Chimie Année : 2002

Pseudo-tetrahedral semi-sandwich cycloruthenated compounds: 1H NMR data and DFT-calculations about the racemisation process of the ruthenium atom

Résumé

The partial substitution of the acetonitrile ligand of compound 1a [(η6-C6H6)Ru(C6H4-2-CH2NMe2)(NCMe)]+PF6 – by CD3OD was observed while running the 1H NMR spectra of 1a in this solvent, this giving rise to the formation of 1b. In opposition to 1a, the 1H NMR spectrum of 1b is temperature-dependent, as at T > 40 °C the coalescence of the signals of the –CH2NMe2 protons was observed, this being an evidence for the fast racemisation of the Ru centre in 1b at the NMR timescale. DFT-calculations allowed us to envision a likely process for this racemisation. It should take place via the decoordination of the methanol ligand at an early step of the reaction, followed by the inversion of the configuration of the thus-obtained 16 e– species (2). The transition state (3) for this latter reaction was identified and the total free energy of the racemisation was thus calculated, affording a value close to the activation energy found experimentally by 1H NMR (∼13 kcal mol–1 vs ∼15.5 kcal mol–1, respectively).
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Dates et versions

hal-00281232 , version 1 (21-05-2008)

Identifiants

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Mike Robitzer, Vincent Ritleng, Claude Sirlin, Alain Dedieu, Michel Pfeffer. Pseudo-tetrahedral semi-sandwich cycloruthenated compounds: 1H NMR data and DFT-calculations about the racemisation process of the ruthenium atom. Comptes Rendus. Chimie, 2002, 5 (5), pp.467-472. ⟨10.1016/S1631-0748(02)01388-7⟩. ⟨hal-00281232⟩

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