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Abdolkarim Chehregani Rad - One of the best experts on this subject based on the ideXlab platform.

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Yves Canac - One of the best experts on this subject based on the ideXlab platform.

  • NHC Core Phosphonium Ylide-based Palladium(II) Pincer Complexes: The Second Ylide Extremity Makes the Difference.
    Inorganic Chemistry, 2020
    Co-Authors: Rachid Taakili, Christine Lepetit, Cécile Barthes, Amel Goëffon, Carine Duhayon, Dmitry A. Valyaev, Yves Canac
    Abstract:

    The coordinating properties of N-heterocyclic carbene (NHC) (A), phenolate (B), and phosphonium Ylide (C) moieties were investigated systematically through the preparation of a family of NHC, phosphonium Ylide-based pincer ligands, where the third donor extremity can be either an NHC, a phenolate, or a phosphonium Ylide. The overall donor character of such ligands [NHC(AaBbCc)] (a + b + c = 2) was analyzed by comparison of the molecular orbitals (energy and shape), oxidation potentials (Epox), and IR νCO and νCN stretching frequencies of their isostructural pincer Pd(II) complexes [NHC(AaBbCc)PdL][OTf] (L = NCCH3, CO, or CNtBu). The three categories of pincer complexes based on phosphonium Ylides were easily obtained by acidic treatment of their highly stable ortho-metalated Pd(II) precursors prepared in a single step from readily available N-phosphonio-substituted imidazolium salts. Analysis of IR data indicated that NHC and phenolate ligands have a similar donor character but which remains lower than that of the phosphonium Ylide. The impact on catalytic performance of the incorporation of a second strongly donating phosphonium Ylide into the ligand architecture was illustrated in the Pd-catalyzed allylation of aldehydes.

  • Bis-Ylide Ligands from Acyclic Proximal Diphosphonium Precursors
    European Journal of Inorganic Chemistry, 2012
    Co-Authors: Carine Maaliki, Cécile Barthes, Carine Duhayon, Yves Canac, Mohammed Abdalilah, Remi Chauvin
    Abstract:

    1,2‐ or 1,3‐Phenylene‐diphosphonium bis‐Ylides have been prepared and their stabilities compared by analysis of the effects of the substitution pattern of the phenylene bridge and the steric hindrance of the P‐alkyl substituents in the diphosphonium precursors RPh2P+(C6H4)+PPh2R′ (R,R′ = Me, Et). In the o‐phenylene series, the vicinity of the phosphorus centers allows the distal P+/C– charge separation of the mono‐Ylide intermediate to be canceled by the formation of a cyclic ylidophosphorane. The ring strain in the latter was released through phenylene–P(σ5) bond cleavage to afford relaxed diphosphonium bis‐Ylides, which were isolated as carbodiphosphorane, or protonated in situ to form bis‐phosphonium Ylides depending on the bulkiness of the P‐alkyl substituents. In the m‐phenylene series (with R,R′ = Me), the amplified distal P+/C– charge separation proved sufficient to stabilize the corresponding diphosphonium bis‐Ylide as a chelating ligand of an RhI(CO)2 center, in a complex where the effective σ‐donation of the ligand was confirmed by comparison of the IR carbonyl stretching frequencies with those of the isostructural complex previously described in the o‐phenylene series

  • Towards the stability limit of cyclic diphosphonium bis-Ylides
    Comptes Rendus Chimie, 2010
    Co-Authors: Mohammed Abdalilah, Christine Lepetit, Yves Canac, Remi Chauvin
    Abstract:

    A typology of molecules containing two phosphonium Ylide groups (bis-Ylides) is proposed, versus the bridge length (fused, ω- and α-bisYlides) and their relative topographical orientations (head-to-head, tail-to-tail or head-to-tail). The formal electrostatic constraint occurring in the head-to-head series is systematically addressed for cyclic representatives based on the o-bis(diphenylphosphonio)benzene framework. After a survey of previously reported results in the fused and β-bis-Ylide series, emphasis is given to the cyclic α-bis-Ylides. The non-substituted, non-stabilized version escaped isolation through spontaneous fragmentation to bis(diphenylphosphino)benzene and acetylene. Inspired by this result, the reverse process was employed for the generation of stabilized representatives with ethoxycarbonyl and benzoyl substituents at the ylidic carbon atoms. The stability and stereochemistry of the obtained head-to-head α-bis-Ylides was investigated by NMR techniques and reproduced and analyzed by DFT calculations. The role of electrostatics in determining structural and reactivity features of cyclically constrained species is here illustrated.

  • Synthesis of Transient and Stable C-Amino Phosphorus Ylides and Their Fragmentation into Transient and Stable Carbenes
    Journal of the American Chemical Society, 2006
    Co-Authors: Yves Canac, Salvador Conejero, Michele Soleilhavoup, Bruno Donnadieu, Guy Bertrand
    Abstract:

    Only basic phosphines, such as tris(dimethylamino)phosphine, allow for the synthesis of a stable acyclic β-amino phosphonium salt 1c, which upon deprotonation with butyllithium affords the corresponding stable C-amino phosphorus Ylide 2c. In contrast, cyclic β-amino phosphonium salts 5a and 5b are stable despite the presence of weakly basic triarylphosphine fragments. They are prepared by intramolecular insertion of the carbene center of (amino)(phosphonio)carbenes into the CH bond of a phosphorus substituent. Deprotonation of 5a leads to the corresponding cyclic C-amino phosphorus Ylide 6a, which has been fully characterized including an X-ray diffraction study. Deprotonation of 5b affords enamine 8, probably via fragmentation of Ylide 6b into transient carbene 7b and a subsequent 1,2-hydrogen shift. Transient cyclic C-amino phosphorus Ylides 6c and 6d have been prepared by intramolecular addition of a carbanion generated by deprotonation of a phosphorus substituent. Three-membered heterocycle 6c rearran...

Zhefeng Li - One of the best experts on this subject based on the ideXlab platform.

Seyyed Javad Sabounchei - One of the best experts on this subject based on the ideXlab platform.