Guy Lavigne

Ether-induced rate enhancement of Mo-catalyzed alkyne metathesis under mild conditions

A “user-friendly” catalyst system generated in situ in the absence of alkyne from Mo(CO)6, p-chlorophenol and a polyether over a bed of molecular sieves, is seen to achieve the metathesis of phenylpropyne at 50°C with a significant rate enhancement depending on the nature of the ether, with 1,2-diphenoxyethane exhibiting the highest efficiency.

Buchwald-Hartwig Amination of (Hetero)Aryl Tosylates Using a Well-Defined N-Heterocyclic Carbene/Palladium(II) Precatalyst.

The cross-coupling of aryl tosylates with amines and anilines was achieved by using for the first time a Pd-NHC system based on the popular Pd-PEPPSI precatalyst platform in which the anchoring imidazol-2-ylidene ligand IPr((NMe2)2) incorporates two dimethylamino groups as backbone substituents enhancing both the electronic and steric properties of the carbene. The system optimization and its application scope are disclosed.

Novel Polymeric Carbonylhaloruthenium(I) Polyanions: Rational Design and Self‐Reorganization in the Presence of CO2 and H2O

We just need to mix [Ru(CO)(3)Cl(2)(thf)] with methanolic NEt(4)OH-nature will do the rest: The unsaturated fragments thus generated spontaneously polymerize with production of CO(2) and H(2)O, which combine to give the carbonate ligands of the ruthena-crown species obtained (shown schematically). The carbonate groups, rarely seen in ruthenium carbonyl complexes, are responsible for the observed annulation, and hold consecutive Ru dimers together by acting as bridging and doubly chelating ligands.

The Subtle Art of Bimetallic Activation: Juggling Carbenes, Hydrocarbons, and Hydride Ligands Between Metals

The selective redistribution of hydrocarbon chains C(n ) on a polyhydrido triruthenium cyclopentadienyl complex (see scheme; Ruu2005red spheres) involves a repeated sequence of face‐to‐face C-H group transfers (A to C ) through the open cluster B , followed by individual concerted skeletal rearrangements on the two faces (C to A′ ). This process is just one of several spectacular examples illustrating the power of a molecular polymetallic system.

New insight into a convenient base-promoted synthesis of Ru3(CO)12

The addition of two equivalents of KOH per Ru under 1 atm CO at 75 °C to a mixture of [Ru(CO)2Cl2]n and [Ru(CO)3Cl2]2 generated in situ by carbonylation of 5 grams of RuCl3·3H2O in 2-ethoxyethanol, triggers a reaction cascade producing Ru3(CO)12 in yields exceeding 90% within 45 minutes.

Buttressing Effect as a Key Design Principle towards Highly Efficient Palladium/N-Heterocyclic Carbene Buchwald–Hartwig Amination Catalysts

The backbone substitution of the standard 1,3-bis(2,6-diisopropylphenyl)-2H-imidazol-2-ylidene (IPr) ligand by dimethylamino groups was previously shown to induce a dramatic improvement in the catalytic efficiency of the corresponding Pd-PEPPSI (pyridine-enhanced pre-catalyst preparation, stabilization, and initiation) pre-catalysts in N-arylation reactions. Herein, a thorough structure/activity study towards rationalizing this beneficial effect has been described. In addition to the previously reported IPrNMe2 and IPr(NMe2)2 ligands, the new IPrNiPr2 and IPr(NMe2,Cl) ligands, which bear one bulkier diisopropylamino group and a combination of dimethylamino and chloro substituents, respectively, have been designed and analyzed in the study. The influence of the backbone substitution was found to be steric in origin and is related to the well-known buttressing effect encountered in arene chemistry. The usefulness and versatility of this approach was demonstrated through the development of a highly efficient catalytic system for the challenging arylation of bulky α,α,α-trisubstituted primary amines. The optimized system based on the [PdCl(η3 -cinnamyl)(IPr(NMe2)2 )] or [PdCl(η3 -cinnamyl)(IPrNiPr2 )] pre-catalysts operates under unprecedented mild conditions (catalyst loadings: 0.5-2u2005molu2009%, reaction temperatures: 40-60u2009°C) with a wide substrate scope.

X-ray and neutron diffraction studies of the hydridotriruthenium cluster complex (μ-H)Ru3(CO)7(μ-As(C6H5)CH2As(C6H5)2) ((C6H52AsCH2As(C6H5)·CH2Cl2: an example of dibridged metal-metal bond M(μ-H)(μ-X)M, involving a heavy bridgehead atom

The title compound is (μ-H)Ru3(CO)7(μ-As(C6H5)CH2As(C6H5)2)((C6H5)2 AsCH2As(C6H5)2)·CH2C12. Crystal data: monoclinic,P21/n, cell parameters (X-ray)a=12.82(2) Å,b=22.91(2) Å,c=17.83(2) Å, β=99.1(3)°; (neutron)a=12.94(1) Å, β=22.95(2)Å,c=17.93(3)Å,β=99.55(5)°. The structure was solved from X-ray data. FinalR indices areR(F)=0.051,Rw(F)=0.049 (X-ray);R(F)=0.064,Rw(F)=0.048,R(F2)=0.072,Rw(F2)=0.088 (neutron). The complex is derived from Ru3(CO)8(dpam)2 through reaction with hydrogen. The structure consists of a triangular array of metal atoms involving three metal-metal bonds[Ru(1)−Ru(2)=2.912(7)Å;Ru(1)−Ru(3)=2.829(3) A; Ru(2)−Ru(3)=2.845(6) Å]. The metal-metal edge Ru(1)−Ru(2) is supported by a bridging bis(diphenylarsino)methane ligand which lies in the equatorial plane. Activation of the second dpam ligand has generated the new face-bridging ligand unit μ-As(C6H5)CH2As(C6H5)2. In this unit, the bridgehead As atom spans over the Ru(1)−Ru(2) bond, while the second As atom is only bonded to Ru(3). The metal environment is achieved by CO ligands. The hydride ligand is bridging the Ru(1)−Ru(2) vector [Ru(1)−H=1.791(10) Å; Ru(2)−H=1.818(8) Å]. Geometric features of the dibridged Ru(μ-H)(μ-As)Ru bond are discussed.