Yves Chauvin

Influence of the self-organization of ionic liquids on the size of ruthenium nanoparticles: effect of the temperature and stirring

The size of ruthenium nanoparticles is governed by the degree of self-organization of the imidazolium based ionic liquid in which they are generated from (η4-1,5-cyclooctadiene)(η6-1,3,5-cyclooctatriene)ruthenium: the more structured the ionic liquid, the smaller the size.

Organized 3D-alkyl imidazolium ionic liquids could be used to control the size of in situ generated ruthenium nanoparticles?

The synthesis of ruthenium nanoparticles, RuNPs from the organometallic complex (η4-1,5-cyclooctadiene)(η6-1,3,5-cyclooctatriene)ruthenium(0), Ru(COD)(COT) in various imidazolium derived ionic liquids, ILs: [RMIm][NTf2] (R = CnH2n + 1 with n = 2; 4; 6; 8; 10), and [R2Im][NTf2] (RBu) and [BMMIm][NTf2] has been performed, under 0.4 MPa of H2, at 25 °C or at 0 °C with or without stirring. A relationship between the size of IL non-polar domains calculated by molecular dynamics simulation and the RuNP size measured by TEM has been found, suggesting that the phenomenon of crystal growth is probably controlled by the local concentration of Ru(COD)(COT) and consequently is limited to the size of the non-polar domains. Moreover, the rigid 3D organization based on C2–H⋯anion bonding and chosen experimental conditions, could explain the non-aggregation of RuNPs.

Interaction between the π-System of Toluene and the Imidazolium Ring of Ionic Liquids: A Combined NMR and Molecular Simulation Study

The solute-solvent interactions and the site-site distances between toluene and ionic liquids (ILs) 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [BMMIm][NTf2] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIm][NTf2] at various molar ratios were determined by NMR experiments (1D NMR, rotating-frame Overhauser effect spectroscopy (ROESY)) and by molecular simulation using an atomistic force field. The difference in behavior of toluene in these ILs has been related to the presence of H-bonding between the C2-H and the anion in [BMIm][NTf2] generating a stronger association (>20 kJ.mol-1) than in the case of [BMMIm][NTf2]. Consequently, toluene cannot cleave this H-bond in [BMIm][NTf2] which remains in large aggregates of ionic pairs. However, toluene penetrates the less strongly bonded network of [BMMIm][NTf2] and interacts with [BMMIm] cations.

Imidazolium ionic liquids as promoters and stabilising agents for the preparation of metal(0) nanoparticles by reduction and decomposition of organometallic complexes

The organometallic complexes ([Ru(COD)(2-methylallyl)2] and [Ni(COD)2] (COD=1,5-cyclooctadiene) dissolved in imidazolium ionic liquids (ILs) undergo reduction and decomposition, respectively, to afford stable ruthenium and nickel metal(0) nanoparticles (Ru(0)-NPs and Ni(0)-NPs) in the absence of classical reducing agents. Depending on the case, the reduction/auto-decomposition is promoted by either the cation and/or anion of the neat imidazolium ILs.

A novel stabilisation model for ruthenium nanoparticles in imidazolium ionic liquids: in situ spectroscopic and labelling evidence

In situ labelling and spectroscopic experiments are used to explain the key points in the stabilisation of ruthenium nanoparticles (RuNPs) generated in imidazolium-based ionic liquids (ILs) by decomposition of (eta(4)-1,5-cyclooctadiene)(eta(6)-1,3,5-cyclooctatriene)ruthenium(0), Ru(COD)(COT), under dihydrogen. These are found to be: (1) the presence of hydrides at the RuNP surface and, (2) the confinement of RuNPs in the non-polar domains of the structured IL, induced by the rigid 3-D organisation. These results lead to a novel stabilisation model for NPs in ionic liquids.

Intramolecular O–H ⋯ O–Ni and N–H ⋯ O–Ni hydrogen bonding in nickel diphenylphosphinoenolate phenyl complexes: role in catalytic ethene oligomerisation; crystal structure of [NiPH{Ph2PCHC(O)(o-C6H4NHPh)}(PPh3)]

Nickel diphenylphosphinoenolate complexes are prepared from ortho-HX-substituted phenacylidenetriphenylphosphoranes (X = O, NMe, NPh) which display strong intramolecular hydrogen bonding between the enolate oxygen and the H–X function; this feature dramatically influences the molecular mass distribution of the oligomers obtained by catalytic oligomerisation of ethene.

Synthesis and characterization of ionic liquids based upon 1-butyl-2,3-dimethylimidazolium chloride/ZnCl2

Trialkylimidazolium chlorozincate molten salts resulting from the combination of zinc chloride and 1-butyl-2,3-dimethylimidazolium chloride, [BMMI][Cl], have been prepared with a mole percent of ZnCl2, R (R = nZnCl2/nZnCl2 + n[BMMI][Cl]) equal to 0, 0.1, 0.25, 0.33, 0.5, 0.66, 0.75. Their analyses by DSC, 13C, 1H and 35Cl solid state and solution NMR, and mass spectrometry (ESI, MS/MS) are consistent with the presence of [BMMI][Cl] and [BMMI][ZnCl3] for R < 0.5; pure [BMMI][ZnCl3] for R = 0.5, and [BMMI][ZnCl3] with [BMMI][Zn3Cl7] for R > 0.5. Infrared spectra realized in the presence of pyridine show that the Lewis acidity of ZnCl2–[BMMI][Cl] increases with R. High temperature (110 °C) 13C and 35Cl NMR experiments on neat [BMMI][ZnCl3] (R = 0.5) evidenced that its structure varies with time from [BMMI][ZnCl3] to [BMMI⋯Cl⋯ZnCl2].

How do Physical—Chemical Parameters Influence the Catalytic Hydrogenation of 1,3-Cyclohexadiene in Ionic Liquids?

The catalytic hydrogenation of 1,3-cyclohexadiene using [Rh(COD)(PPh(3))(2)]NTf(2) (COD = 1,5-cyclooctadiene) was performed in two ionic liquids: 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(4)Im][NTf(2)], and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(1)C(4)Im][NTf(2)]. It is observed that the reaction is twice as fast in [C(1)C(4)Im][NTf(2)] than in [C(1)C(1)C(4)Im][NTf(2)]. To explain the difference in reactivity, molecular interactions and the microscopic structure of ionic liquid +1,3-cyclohexadiene mixtures were studied by NMR and titration calorimetry experiments, and by molecular simulation in the liquid phase. Diffusivity and viscosity measurements allowed the characterization of mass transport in the reaction media. We could conclude that the diffusivity of 1,3-cyclohexadiene is 1.9 times higher in [C(1)C(4)Im][NTf(2)] than in [C(1)C(1)C(4)Im][NTf(2)] and that this difference could explain the lower reactivity observed in [C(1)C(1)C(4)Im][NTf(2)].

A silver and water free metathesis reaction: a route to ionic liquids

A versatile, cheaper, silver and water-free metathesis reaction was developed for imidazolium, phosphonium and pyrrolidinium based ionic liquids (ILs) associated with different anions such as dicyanamide, thiocyanate, tetrafluoroborate and bis(trifluoromethylsulfonyl)imide. This route, using the melt of amine chloride as a solvent and reagent, favours the ion exchange reaction using anion salts of Na or Li, yielding ionic liquids in high purity (≥99.5%) and high yields (≥90%). This route is particularly well adapted for water miscible ILs preparation.

Phenyl nickel complexes with a chelating P,N ligand. Structures of Ph3PCHC(NPh)Ph and [NiPh{Ph2PCHC)NPh)Ph}-{Ph3PCHC(NPh)Ph-N}]

The complexes [[graphic omitted]Ph)Ph}{Ph3PCHC(NPh)Ph-N}] and [[graphic omitted]Ph)Ph}(PR3)](PR3= PMe3, PMe2Ph or PMePh2) were prepared starting from [Ni(cod)2](cod = cycloocta-1,5-diene) and the phosphorus ylide Ph3PCHC(NPh)Ph I in the presence of a tertiary phosphine. Surprisingly, only the first complex was isolated when PPh3 and P(C6H11)3 were used, whereas the other phosphines led to the corresponding PR3 complexes together with variable amounts of the first depending on their steric demand. The known synthesis of I has been optimized to yields close to 90%. Experiments carried out to study the potential of the nickel compounds as catalysts for ethylene oligomerization showed the stoichiometric formation of styrene and minor amounts of low-molecular-weight linear α-olefins. The molecular structures of I and the first complex have been determined by X-ray diffraction. In the nickel complex the coordination around the metal is distorted square planar, with P(1)–Ni–C(1) and N(1)–Ni–N(2) angles of 90.30(8) and 97.18(8)°, respectively.