C–F Bond Breaking through Aromatic Nucleophilic Substitution with a Hydroxo Ligand Mediated via Water Bifunctional Activation

Abstract

Transformation of CF to CO bond mediated by bifunctional ruthenium and iridium complexes is described. This reaction proceeds through water OH bond cleavage via metalligand cooperation in the newly developed 16e bifunctional ruthenium and iridium complexes bearing chiral (S,S)-C 6 F 5 SO 2 -dpen ligand. The 16e Ru amido complex, [Ru{(S,S)-Pfbsdpen}(η 6 -hmb)] (1a), readily reacted with water at room temperature producing oxometallacyclic compound, (R)- [Ru{κ 3 (N,N¤,O)-(S,S)-OC 6 F 4 SO 2 dpen}(η 6 -hmb)] (3a R ), as a result of bifunctional water activation followed by ortho-oxometallation via S N Ar. Complex 3a R can be prepared either from 1a or, more conveniently from its 18e chlorido precursor, complex (R)-[RuCl{(S,S)-Pfbsdpen}(η In either case 3 R or 4 R 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 ¼ 3a R proceeds at temperatures >0°C in a stepwise manner through the detectable intermediate, hydroxo complex (R)-[Ru(OH){(S,S)-Pfbsdpen}(η 6 -hmb)] (6a R ), which exists in equilibrium with less-populated diastereomer (S)-[Ru(OH){(S,S)-Pfbsdpen}(η 6 -hmb)] (6a S ) in 10:1 ratio at ¹80°C in CD 2 Cl 2 . Computational analysis essentially explains the diastereoselectivity in this reaction via a significant difference in the stabilities of the corresponding transition states: although diastereomers 6a R and 6a S are in equilibrium via complex 1a, only 6a R is transformed into 3a R via ratedetermining Meisenheimer-type transition state.In the last few decades, bifunctional molecular catalysis based on metalligand cooperation has been rapidly developed and has become a general strategy for highly efficient molecular transformations in synthetic organic chemistry. 1,2We have successfully developed a series of half-sandwich-type bifunctional Ru and Ir catalysts, [Ru(N-sulfonylated dpen)-(η 6 -arene)] and [Cp*Ir(N-sulfonylated dpen)], bearing the chelating chiral N-sulfonylated diamine ligands (dpen: 1,2-diphenylethylenediamine) for a wide range of molecular transformations. They include practical asymmetric transfer hydrogenation of ketones 3 and imines, 4 asymmetric hydrogenation of polar functionalities, 5 asymmetric Michael reaction of 1,3-dicarbonyl compounds with cyclic enones 6 and nitroalkenes, 7 stereoselective catalytic CN 8 and CC 8b,9 bondforming reactions, aerobic oxidative kinetic resolution of racemic secondary alcohols 10 and asymmetric hydration of nitriles.11 The key to success in these catalytic reactions relies on the intrinsic nature of the 16e amido complexes to activate reversibly XH ¤+ bonds (X = H ¤¹ , C, O, N) via the metalligand cooperation with no change in the formal oxidation state of the metal (bifunctional activation). For example, facile reversible...

Cleavage of N–H Bond of Ammonia via Metal–Ligand Cooperation Enables Rational Design of a Conceptually New Noyori–Ikariya Catalyst

“…Thanks to the combination of a Lewis acid and Lewis base within a single molecule, the well-defined 16e – chiral Ru amido complex 1 reversibly cleaves the H–H bond of hydrogen, , O–H bond of water or secondary alcohols, C–H bond of several 1,3-dicarbonyl compounds, and N–H bond of sulfonamides as shown at the top of Scheme …”

Nucleophilic Aromatic Substitution in Hydrodefluorination Exemplified by Hydridoiridium(III) Complexes with Fluorinated Phenylsulfonyl-1,2-diphenylethylenediamine Ligands

“…The distinct reactivity between hydrido complexes 3a and 3b are totally consistent with the nucleophilic substitution mechanism, which should be influenced by differences in the electron deficiency of the Fs and Fs H moieties. , In this context, we have already reported an intramolecular S N Ar-type substitution reaction using the related hydroxido-ruthenium and iridium complexes derived from the FsDPEN ligand (Scheme ). The mechanistic validity of the nucleophilic attack to the Fs group by the hydroxido ligand was supported by DFT calculations.…”

“…3b,10 In this context, we have already reported an intramolecular S N Ar-type substitution reaction using the related hydroxido-ruthenium and iridium complexes derived from the FsDPEN ligand (Scheme 16). 29 The mechanistic validity of the nucleophilic attack to the Fs group by the hydroxido ligand was supported by DFT calculations.…”

Synthesis of a Half-Sandwich Hydroxidoiridium(III) Complex Bearing a Nonprotic N-Sulfonyldiamine Ligand and Its Transformations Triggered by the Brønsted Basicity

“…During the course of our studies on bifunctional catalysis based on the interconversion of amido/amine ligands [6], the O-H bond of water proved to be cleaved heterolytically by chiral amido-Ru complexes to generate amine-hydroxido complexes, and the process can contribute to the hydration of dinitriles in an enantioselective manner (Scheme 1a) [7]. Separately, we also reported the C-F bond breaking through nucleophilic aromatic substitution with a coordinated OH group generated from water and bifunctional amido-Ru and -Ir complexes (Scheme 1b) [8]. In these systems, the hydroxido complexes could not be isolated, possibly because the basicity of the hydroxido ligand promoted the reverse deprotonation of the protic amine ligands to give the parent amido complexes.…”