C-F bond breaking through aromatic nucleophilic substitution with a hydroxo ligand mediated via water bifunctional activation

Pavel A. Dub, Hui Wang, Asuka Matsunami, Ilya D. Gridnev, Shigeki Kuwata, Takao Ikariya

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17 Citations (Scopus)

Abstract

Transformation of C-F to C-O bond mediated by bifunctional ruthenium and iridium complexes is described. This reaction proceeds through water O-H bond cleavage via metal-ligand cooperation in the newly developed 16e bifunctional ruthenium and iridium complexes bearing chiral (S,S)-C6F 5SO2-dpen ligand. The 16e Ru amido complex, [Ru{(S,S)-Pfbsdpen}(η6-hmb)] (1a), readily reacted with water at room temperature producing oxometallacyclic compound, (R)- [Ru{κ3(N,N′,O)-(S,S)-OC6F4SO 2dpen}(η6-hmb)] (3aR), as a result of bifunctional water activation followed by ortho-oxometallation via S NAr. Complex 3aR can be prepared either from 1a or, more conveniently from its 18e chlorido precursor, complex (R)-[RuCl{(S,S)-Pfbsdpen} (η6-hmb)]. On the contrary, the 16e Ir amido complex, [Cp*Ir{(S,S)-Pfbsdpen}] (2), is kinetically stable toward water at room temperature. Oxometallacyclic compound (R)-[Cp*Ir{κ3(N, N′,O)-(S,S)-OC6F4SO2dpen}] (4 R) was prepared in high yield by the reaction of [Cp*IrCl 2]2 with 2 equiv of (S,S)-Pfbsdpen in the presence of KOH under reflux in THF. In either case 3R or 4R is obtained as a single diastereomer, the structure of which has been determined by single-crystal X-ray diffraction studies in solid state and NMR-analysis in solution. Reaction mechanism was studied by NMR spectroscopy combined with continuum solvent reaction-field density functional theory (DFT) analysis. Experimental studies showed that diastereoselective oxocyclometallation 1a→3aR proceeds at temperatures >0 °C in a stepwise manner through the detectable intermediate, hydroxo complex (R)-[Ru(OH){(S,S)- Pfbsdpen}(η6-hmb)] (6aR), which exists in equilibrium with less-populated diastereomer (S)-[Ru(OH){(S,S)-Pfbsdpen}(η6- hmb)] (6aS) in 10:1 ratio at -80 °C in CD2Cl 2. Computational analysis essentially explains the diastereoselectivity in this reaction via a significant difference in the stabilities of the corresponding transition states: although diastereomers 6aR and 6aS are in equilibrium via complex 1a, only 6aR is transformed into 3aR via ratedetermining Meisenheimer-type transition state.

Original languageEnglish
Pages (from-to)557-568
Number of pages12
JournalBulletin of the Chemical Society of Japan
Volume86
Issue number5
DOIs
Publication statusPublished - 2013
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)

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