9,10-Dihydroanthracenyl structures: original ligands for the synthesis of polymetallic complexes through selective π-coordination.

N-Phenylsuccinimides and the corresponding pyrrolidines containing 9,10-dihydroanthracenyl skeletons were used for exploring their ability to coordinate RuCp(+) moieties through the aromatic rings. Electronic and steric tuning of ligands led to mono-, bi- and tri-metallic complexes. A full structural study was carried out in order to characterize the ruthenium organometallic compounds, proving the different coordination modes both in solution (NMR) and in solid state (X-ray diffraction). A modelling study (at DFT level) was completed with the aim to understand the selective π-coordination observed for mono- and bi-metallic complexes.

Tris(η(5)-cyclo-penta-dien-yl)-tris-[η(6)-[9,10-dihydro-anthracene-9,10-endo-3',4'-(N-benz-yl)pyrrolidine]]triruthenium(II) tris-(hexa-fluoro-phosphate) acetone disolvate.

In the title compound, [Ru(3)(C(25)H(23)N)(C(5)H(5))(3)]·3PF(6)·2C(3)H(6)O], the cation is a triruthenium complex of a 9,10-dihydro-anthracene derivative. Three RuCp(+) (Cp is cyclo-penta-dien-yl) groups are bonded to the three aromatic rings of the ligand. Surprisingly, the pyramidalized N atom of the heterocycle (Σ C-N-C = 329.0°) points towards the anthracenyl group, so losing its coordinative ability. There is an inter-molecular C-H⋯π inter-action involving an acetone mol-ecule and the adjacent benzyl ring of the ligand. In the crystal, mol-ecules are linked via a number of C-H⋯O and C-H⋯F inter-actions and a C-H⋯π inter-action, leading to the formation of a three-dimensional supra-molecular structure. One of the Cp groups is disordered over two positions, with refined occupancies of 0.695 (14):0.305 (14). Two of the three hexa-fluoro-phospate anions are disordered, with refined occupancies of 0.630 (6):0.370 (6) and 0.771 (8):0.229 (8). One of the two solvent acetone mol-ecules is also disordered, with refined occupancies of 0.82 (2):0.18 (2).

(1S,8R,15S,19R)-17-Benzyl-17-aza-penta-cyclo-[6.6.5.0(2,7).0(9,14).0(15,19)]nona-deca-2(7),3,5,9(14),10,12-hexa-ene chloro-form monosolvate.

In the title compound, C(25)H(23)N·CHCl(3), the dihydro-anthracene unit is bent with a dihedral angle between the benzene rings of 57.82 (8)°. The N atom of the pyrrolidine heterocycle, which has an envelope conformation with the N atom as the flap, exhibits a pronounced pyramidalization [Σ(C-N-C) = 328.07°], indicating an accentuated N-donor character. In the crystal, this behaviour is evident by the C-H⋯N hydrogen bond involving a solvent mol-ecule and the N atom. The absolute configuration at the C-atom fused positions of the pyrrolidine group were crystallographically confirmed to be S and R.

A smart palladium catalyst in ionic liquid for tandem processes.

New catalytic systems based on in situ and preformed palladium nanoparticles in ionic liquids (characterised by TEM) starting from palladium acetate or dipalladiumtris(dibenzylideneacetone) have been applied in the synthesis of 4-phenylbutan-2-one (II), a model compound for the preparation of fragrances. Imidazolium-based ionic liquid containing a methyl hydrogenophosphonate anion leads to an efficient Pd-catalyzed tandem coupling/reduction process, taking advantage of the multi-role of this solvent (nanoparticles stabiliser, base, hydrogen transfer agent). The influence of the mono-phosphine ligands (1-3) on the catalyst has been evaluated, showing that the ligand-free palladium system turns into the most appropriate for the formation of II using Pd(OAc)(2) as precursor. Fine-tuning conditions involved in this multi-parameter process have led us to propose a plausible mechanism based on the hydrogen transfer coming from the methyl hydrogenophosphonate anion.

Efficient recycling of a chiral palladium catalytic system for asymmetric allylic substitutions in ionic liquid.

Chiral carbohydrate-based diphosphites were used for Pd-catalysed asymmetric allylic substitution (alkylation, amination, phosphination) in neat ionic liquids (ILs). Pyrrolidinium-based IL led to the best activities, allowing an efficient catalyst immobilization. In the allylic amination (TOF > 3100 h(-1)), the catalyst could be recycled nine times preserving both activity and enantioselectivity.

Unexpected activation of carbon-bromide bond promoted by palladium nanoparticles in Suzuki C-C couplings.

Dihydroanthracene derivatives (1-6) containing imide (1-3) and amine (4-6) functions have been used for the stabilization of palladium nanoparticles, starting from Pd(0) and Pd(ii) organometallic precursors. Well-dispersed nanoparticles of mean size in the range ca. 1.9 to 3.6 nm could be obtained using Pd(0) precursors (PdLc and PdLd, where L = 1-6 and c and d mean the organometallic precursor involved, [Pd(2)(dba)(3)] and [Pd(ma)(nbd)] respectively). With the aim to evaluate the behaviour of homogeneous species and nanoparticles used as catalytic precursors, palladium complex coordinated to the diamine 6, [Pd(OAc)(2)(κ(2)-N,N-6)], was prepared, reporting for the first time the X-ray diffraction structure of a metallic complex containing a ligand with a 9,10-dihydroanthracene backbone. Palladium systems were evaluated in Suzuki C-C coupling reactions and relevant differences were observed comparing the reactivity of the homogeneous systems in relation to that obtained using palladium nanoparticles as starting catalyst in relation to the activation of the C-Br bonds for deactivated substrates.

Imidazolium-based ionic liquids immobilized on solid supports: effect on the structure and thermostability.

[BMI][PF(6)] has been supported on silica and alumina in order to study the effect of these classical oxide supports on the structure of the ionic liquid. A widespread characterization by TGA, DSC, XRD and solid NMR of thin films of [BMI][PF(6)] immobilized on these amorphous supports has evidenced a dramatic effect on the ionic liquid structure depending on the nature of the support. For the alumina composite, a loss of the supramolecular arrangement of the ionic liquid occurs, while for the analogous silica composite, ions interact strongly with the support, leading to a [BMI][PF(6)] thermostability decrease.

An outstanding palladium system containing a C2-symmetrical phosphite ligand for enantioselective allylic substitution processes.

The use of efficient Pd systems bearing C(2)-symmetric chiral diphosphite ligands derived from carbohydrates in asymmetric allylic substitution reactions is described here, reaching TOFs > 22 000 h(-1) in allylic alkylation and ca. 400 h(-1) in allylic amination, giving excellent enantioselectivities (ee > 99%) and kinetic resolution of the racemic substrate.

Supported ionic liquid phase catalysis on functionalized carbon nanotubes.

Highly active rhodium catalysts have been prepared by immobilization of an ionic liquid film on carbon nanotubes functionalized with imidazolium-based ionic moieties.

A new and specific mode of stabilization of metallic nanoparticles.

We report in this paper the stabilization of ruthenium nanoparticles using a very simple ligand (4-(3-phenylpropyl)pyridine), through strong pi-coordination of the phenyl moiety.

DOSY technique applied to palladium nanoparticles in ionic liquids.

Multinuclear ((1)H, (31)P, (19)F and (11)B) diffusion ordered spectroscopy (DOSY) technique has been applied to palladium nanoparticles systems dispersed in ionic liquids (ILs). Even if the nanoparticles themselves cannot be detected through NMR, observation of the solvent (methanol) and the IL ([BMI][PF(6)] or [BMI][NTf(2)]), their diffusion coefficients and their changes in the presence of nanoparticles allow us to draw significant assumptions about the organisation of palladium nanoparticles in the IL. For comparison, the corresponding molecular precursors ([PdCl(2)(cod)] or [Pd(2)(dba)(3)]) have been also studied.

Palladium catalyzed Suzuki C-C couplings in an ionic liquid: nanoparticles responsible for the catalytic activity.

A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C-C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF(6)] (BMI=1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case. Some tests, including the correlation effect between solvent and ligand, are carried out to try to identify the true nature of the catalyst. All the results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system.

A Stable (Amino)(Phosphino)Carbene as bidentate ligand for Palladium and Nickel Complexes: Synthesis, Structure, and Catalytic Activity.

Two original complexes featuring an (amino)(phosphino)carbene η(2)-bonded to the metal have been obtained in 60 and 80 % yields, by addition of the corresponding stable carbene to PdCl(2)(cod) and NiCl(2)(PPh(3))(2), respectively. Both complexes have been fully characterized including X-ray diffraction studies. The catalytic activity of the palladium complex has been evaluated for aryl amination reactions.