Dérivés ambiphiles : coordinations inusuelles et applications en catalyse

Phosphine–Borane Ligands Induce Chemoselective Activation and Catalytic Coupling of Acyl Chlorides at Palladium
M. Boudjelel, O. Sadek, S. Mallet-Ladeira, Y. García-Rodeja, E. D. Sosa Carrizo, K. Miqueu, G. Bouhadir, D. Bourissou
ACS Catal. 2021, ASAP

1,1-Phosphaboration of C≡C and C=C bonds at gold
C. A. Theulier, Y. García-Rodeja, N. Saffon-Merceron, K. Miqueu, G. Bouhadir, D. Bourissou
Chem. Commun., 2021,57, 347-350

Fluorosilane Activation by Pd/Ni→Si–F→Lewis Acid Interaction: An Entry to Catalytic Sila-Negishi Coupling
H. Kameo, H. Yamamoto, K. Ikeda, T. Isasa, S. Sakaki, H. Matsuzaka, Y. García-Rodeja, K. Miqueu, D. Bourissou
J. Am. Chem. Soc. 2020, 142, 33, 14039–14044

Palladium–Borane Cooperation: Evidence for an Anionic Pathway and Its Application to Catalytic Hydro‐/Deutero‐dechlorination
Kameo, J. Yamamoto, A. Asada, H. Nakazawa, H. Matsuzaka, D. Bourissou
Angew. Chem. Int. Ed., 2019, 58, 18783-18787

Metal–Lewis acid cooperation provides new opportunities in catalysis. In this work, we report a new type of palladium–borane cooperation involving anionic Pd⁰ species. The air‐stable DPB palladium complex 1 (DPB=diphosphine‐borane) was prepared and reacted with KH to give the Pd⁰ borohydride 2 , the first monomeric anionic Pd⁰ species to be structurally characterized. The boron moiety acts as an acceptor towards Pd in 1 via Pd→B interaction, but as a donor in 2 thanks to B‐H‐Pd bridging. This enables the activation of C−Cl bonds and the system is amenable to catalysis, as demonstrated by the hydro‐/deutero‐dehalogenation of a variety of (hetero)aryl chlorides (20 examples, average yield 85 %).

The first examples of half-sandwich Rh(I) complexes stabilized by borane coordination have been prepared and structurally characterized. As substantiated by NMR spectroscopy and single-crystal X-ray diffraction, the phosphine–borane ligand iPr₂P-(o-C₆H₄)-BFxyl₂ 1 [Fxyl = 3,5-(F₃C)₂C₆H₃] engages in tight η³-BCC or η¹-B coordination, depending on the metal environment.

Catalytic Dehydrogenation of (Di)​Amine-​Boranes with a Geometrically Constrained Phosphine-​Borane Lewis Pair
M. Boudjelel, E. D. Sosa Carrizo, S. Mallet-Ladeira, S. Massou, K. Miqueu, G. Bouhadir, D. Bourissou
ACS Catal., 2018, 8, 4459-4464

The o-phenylene bridged phosphine-borane iPr₂P(o-C₆H₄)B(Fxyl)₂ 2 was prepared. Despite ring strain, it adopts a closed form, as substantiated by NMR, XRD, and DFT analyses. However, the corresponding open form is only slightly higher in energy. The dormant Lewis pair 2 proved to efficiently catalyze the dehydrogenation of a variety of amine- and diamine-boranes under mild conditions. The corresponding phosphonium-borate iPr₂PH(o-C₆H₄)BH(Fxyl)₂ 3 was authenticated as a key intermediate of these dehydrogenation reactions. The propensity of 3 to release H₂ plays a major role in the catalytic turnover.

Complexes of ambiphilic ligands: reactivity and catalytic applications
G. Bouhadir, D. Bourissou*
Chem. Soc. Rev., 2016, 45, 1065-1079.

Since the mid 2000's, the incorporation of Lewis acid moieties in ligands for transition metals has been studied extensively. So-called ambiphilic ligands were shown to possess rich and unusual coordination properties and special focus was given to the coordination of Lewis acids as σ-acceptor ligands (concept of Z-type ligands). Recent studies have demonstrated that the presence of Lewis acids at or nearby transition metals can also strongly impact their reactivity. These results are surveyed in this review. The stoichiometric transformations and catalytic applications of complexes deriving from ambiphilic ligands are presented. The different roles the Lewis acid can play are discussed.

 The P-coordinated boryl radical [Ph₂P(naphthyl)BMes]. (Mes = mesityl) was prepared by (electro)chemical reduction of the corresponding borenium salt or bromoborane. Electron paramagnetic resonance (EPR) analysis in solution and DFT calculations indicate large spin density on boron (60–70 %) and strong P–B interactions (P→B σ donation and B→P negative hyperconjugation). The radical is persistent in solution and participates in a Gomberg-type dimerization process. The associated quinoid-type dimer has been characterized by single-crystal X-ray diffraction.

Borenium cations have been found to be valuable analogues of boranes as a result of their cationic character which imparts high electrophilicity. Herein, we report the synthesis, characterization, and reactivity of a new type of borenium cation employing a naphthyl bridge and a strong intramolecular P®B interaction. The cation reacts with H₂ in the presence of PtBu₃ (frustrated Lewis pair (FLP) approach) but also on its own. The mechanism of the reaction between the borenium cation and H₂ in the absence of PtBu₃ has been investigated using deuterium-labeling experiments and DFT calculations. Both experiments and calculations imply the side-on coordination of H₂ to the B center, followed by heterolytic splitting and B-C bond cleavage. An uncommon syn 1,2-carboboration has also been observed upon reaction of the borenium ion with 3-hexyne.