Laboratory of Chemistry, Catalysis, Polymers and Process

While β-diketiminate (BDI or 'nacnac') ligands have been widely adopted to stabilize a wide range of metal ions in multiple oxidation states and coordination numbers, in several occurrences these ligands do not behave as spectators and participate in reactivity. Besides unwanted decomposition processes, BDI redox non-innnocence and unusual metal-ligand cooperative activation of substrates yielding attractive reactivity have been reported. This feature article will provide a comprehensive analysis of the various transformations involving BDI ligand platforms in coordination compounds across the periodic table.

Supported Lewis acid/base systems based have been prepared and characterized.

We report the synthesis and photo-reactivity of d(0) niobium imido azido complexes supported by β-diketiminate ligands, which leads to the unprecedented formation of nitrides through a photo-assisted intramolecular rearrangement. This provides a new entry to metal nitrides that does not require low-valent metal centers and is a rare example in which the metal-imido moiety in group 5 complexes participates in reactivity.

We report the synthesis and characterization of a series of original tantalum/rhodium heterobimetallic species assembled by a bifunctional alkoxy-N-heterocyclic carbene (NHC) ligand platform (noted L). The heterotrimetallic [Ta(CH2tBu)(CHtBu)(μ-L)Rh2(COD)2Cl2]n, 2, and heterobimetallic [Ta(μ-L)(CHtBu)(CH2tBu)2Rh(COD)Cl], 4, complexes are obtained upon treatment of [Ta(L)(CHtBu)(CH2tBu)2], 1, with [Rh(COD)Cl]2. To avoid parasistic reactivity arising from the neopentylidene fragment in 1, the peralkyl compound {Ta(L)[OSi(OtBu)3](CH2tBu)3}, 5, resulting from the 1,2-addition of tris(tertbutoxysilanol) across the Ta[double bond, length as m-dash]C alkylidene motif, is prepared. An unanticipated silanol-NHC adduct, {HOSiOtBu3}{Ta(L)[OSi(OtBu)3](CH2tBu)3}, 6, is formed when 1 is treated with two equivalents of HOSi(OtBu)3. Finally, treatment of 5 with [Rh(COD)Cl]2 provides the heterobimetallic complex {Ta(μ-L)[OSi(OtBu)3](CH2tBu)3Rh(COD)(Cl)}, 7, in high yield. This work highlights the reactivity of Ta-NHC adducts and the aptitude of the NHC motif to transfer from Ta to Rh which is used with profit as an efficient synthetic route to access early/late heterobimetallic complexes.

Cationic latexes with Tgs ranging between -40 °C and 120 °C were synthesised using n-butyl acrylate (BA) and/or methyl methacrylate (MMA) as the core polymers. Reversible addition-fragmentation chain transfer (RAFT) combined with polymerisation-induced self-assembly (PISA) allowed for in situ chain-extension of a cationic macromolecular RAFT agent (macroRAFT) of poly(N-[3-(dimethylamino)propyl] methacrylamide) (PDMAPMA), used as stabiliser in so-called surfactant-free emulsion polymerisation. The resulting narrowly distributed nanosized latexes adsorbed readily onto silica surfaces and to model surfaces of cellulose nanofibrils, as demonstrated by quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. Adsorption to anionic surfaces increased when increasing ionic strength to 10 mM, indicating the influence of the polyelectrolyte effect exerted by the corona. The polyelectrolyte corona affected the interactions in the wet state, the stability of the latex and re-dispersibility after drying. The QCM-D measurements showed that a lower Tg of the core results in a more strongly interacting adsorbed layer at the solid-liquid interface, despite a comparable adsorbed mass, indicating structural differences of the investigated latexes in the wet state. The two latexes with Tg below room temperature (i.e. PBATg-40 and P(BA-co-MMA)Tg3) exhibited film formation in the wet state, as shown by AFM colloidal probe measurements. It was observed that P(BA-co-MMA)Tg3 latex resulted in the largest pull-off force, above 200 m Nm-1 after 120 s in contact. The strongest wet adhesion was achieved with PDMAPMA-stabilized latexes soft enough to allow for interparticle diffusion of polymer chains, and stiff enough to create a strong adhesive joint. Fundamental understanding of interfacial properties of latexes and cellulose enables controlled and predictive strategies to produce strong and tough materials with high nanocellulose content, both in the wet and dry state.

In this work, a new methodology for the synthesis of well-defined metallic nanoparticles supported on silica is described. This methodology is based on the surface control provided by SOMC. The nanoparticles are formed via the organometallic approach and are catalytically active in the hydrogenation of p-xylene, 3-hexyne, 4-phenyl-2 butanone, benzaldehyde, and furfural.

A rare heterobimetallic oxidative addition of X-H (X = C, O) bonds is reported. DFT suggests that steric constraints around the bimetallic core play a critical role to synergistically activate C-H bonds across the two metals and thus explains the exceptional H/D exchange catalytic activity of unhindered surface organometallic Ta/Ir species observed experimentally.

Alkyl-aluminum(<sc>iii</sc>) derivatives supported by a bifunctional alkoxy-NHC ligand display unusual reactivity at the carbene, yielding imidazolium-aluminate zwitterions.

Zn was found to possess a dual role in composite PdZn–H-ZSM-5 catalysts for CO₂ hydrogenation reactions: it promotes methanol formation when alloyed with Pd, but inhibits hydrocarbon formation by ion exchange with Brønsted acid sites in H-ZSM-5.

Rutile is the most common and stable polymorph form of titanium oxide TiO2 at all temperatures. The doping of rutile TiO2 with a small amount of niobium is reknown for being responsible for a large increase of the electrical conductivity by several orders of magnitude, broadening its technological interest towards new emerging fields such as the thermoelectric conversion of waste heat. The electronic conduction has been found to be of a polaronic nature with strongly localized charges around the Ti3+ centers while, on the other side, the relatively high value of the thermal conductivity implies the existence of lattice heat carriers, i.e. phonons, with large mean free paths which makes the nanostructuration relevant for optimizing the thermoelectric efficiency. Here, the use of a high-pressure and high-temperature sintering technique has allowed to vary the grain size in rutile TiO2 pellets from 300 to 170 nm, leading to a significant reduction of the lattice thermal conductivity. The thermoelectric properties (electrical conductivity, Seebeck coefficient and thermal conductivity) of Nb-doped rutile nanostructured ceramics, namely NbxTi1-xO2 with x varying from 1 to 5%, are reported from room temperature to ∼900 K. With the incorporation of Nb, an optimum in the thermoelectric properties together with an anomaly on the tetragonal lattice constant c are observed for a concentration of ∼2.85%, which might be the fingerprint of the formation of short Nb dimers.

A sustainable nickel-catalyzed direct C–H arylation of benzothiophenes, benzofuran and selenophene is reported for the first time.

Suspensions of bimetallic nanoparticles (NPs) of Ru and Cu have been synthesized by simultaneous decomposition of two organometallic compounds in an ionic liquid. These suspensions have been characterized by Anomalous Small-Angle X-ray Scattering (ASAXS) at energies slightly below the Ru K-edge. It is found that the NPs adopt a Ru-core, a Cu-shell structure, with a constant Ru core diameter of 1.9 nm for all Ru : Cu compositions, while the Cu shell thickness increases with Cu content up to 0.9 nm. The formation of RuCuNPs thus proceeds through rapid decomposition of the Ru precursor into RuNPs of constant size followed by the reaction of the Cu precursor and agglomeration as a Cu shell. Thus, the different decomposition kinetics of precursors make possible the elaboration of core-shell NPs composed of two metals without chemical affinity.

2-Butenes are transformed in a continuous flow reactor over metal hydrides of zirconium, tantalum and tungsten supported on silica–alumina. Exceptionally high selectivity to dimeric products is obtained over supported zirconium hydride catalysts.

A well dispersed Ru–Cu on the HPA catalyst converts pine wood into biofuel (O = 3.1 wt%) with a yield up to 30 wt%.

Mesitylcopper reacts with silica to give supported clusters, then reduced to nanoparticles. These catalysts allow the selective hydrogenation of 2,3-dimethylbutadiene to 2,3-dimethyl-1-butene. Materials were characterized in detail.

, respectively. It is noteworthy that under optimized conditions, a layer of antimony species or suboxides on silica was produced using POSS-Sb without significant Sb loss, highlighting the protective properties of the POSS cage. These results open new perspectives for the controlled and non-destructive Sb-doping (Molecular Layer Doping) of semiconductors dedicated to nano-device applications.

The preferred catalytic cycle occurring in the conversion of isobutene and 2-butene to propylene and pentenes over WH₃/Al₂O₃ has been investigated <italic>via</italic> an energetic analysis of the metallacyclobutanes formed upon 2 + 2 butene cycloaddition with alumina supported tungsten alkylidenes.

Peroxide species appearing in imidazolium-based ionic liquids could be removed by salen–manganese complexes or the enzyme catalase.

A molybdenum disulfide coating deposited on a macroporous substrate as an electrocatalyst is mobile on an underlying amorphous tin dioxide substrate, but remains continuous and impervious to acidic conditions on crystalline tin dioxide.

An improved approach of semi-conductor doping by Molecular Layer Deposition (MLD) is investigated. Here, dopant-containing molecules are directly grafted onto silica-coated silicon wafers and optimized ligands can provide more effective dopant drive-in annealing. The grafting approach is validated on non-porous silica and successfully transferred onto silicon wafers.