Nicolas Mézailles

Catalytic Dinitrogen Reduction at the Molybdenum Center Promoted by a Bulky Tetradentate Phosphine Ligand

Stoichiometric reduction of N2 at a Mo center stabilized by a bulky tetradentate phosphine ligand (PP3(Cy)) allowed isolation of Mo-imidoamine and Mo-imido complexes. Both complexes as well as the Mo(II) precursor are equally suitable catalysts for the synthesis of NTMS3 (TMS = trimethylsilyl) from N2, TMSCl, and electron sources. Mechanistic studies prove the involvement of a TMS radical at least in one of the catalytic steps.

Direct Synthesis of Silylamine from N2 and a Silane: Mediated by a Tridentate Phosphine Molybdenum Fragment

A homogeneous system which is able to yield silylamine from N2 and bis(silane) in one pot is reported. Mechanistically a {(triphosphine)molybdenum(I)} fragment, generated in situ, splits N2 into the corresponding nitrido complex at room temperature. Then, functionalization of the molybdenum nitrido is achieved by double Si-H addition under mild reaction conditions. Moreover, the bis(silyl)amine product is decoordinated from the metal center.

The core contribution of transmission electron microscopy to functional nanomaterials engineering

Research on nanomaterials and nanostructured materials is burgeoning because their numerous and versatile applications contribute to solve societal needs in the domain of medicine, energy, environment and STICs. Optimizing their properties requires in-depth analysis of their structural, morphological and chemical features at the nanoscale. In a transmission electron microscope (TEM), combining tomography with electron energy loss spectroscopy and high-magnification imaging in high-angle annular dark-field mode provides access to all features of the same object. Today, TEM experiments in three dimensions are paramount to solve tough structural problems associated with nanoscale matter. This approach allowed a thorough morphological description of silica fibers. Moreover, quantitative analysis of the mesoporous network of binary metal oxide prepared by template-assisted spray-drying was performed, and the homogeneity of amino functionalized metal-organic frameworks was assessed. Besides, the morphology and internal structure of metal phosphide nanoparticles was deciphered, providing a milestone for understanding phase segregation at the nanoscale. By extrapolating to larger classes of materials, from soft matter to hard metals and/or ceramics, this approach allows probing small volumes and uncovering materials characteristics and properties at two or three dimensions. Altogether, this feature article aims at providing (nano)materials scientists with a representative set of examples that illustrates the capabilities of modern TEM and tomography, which can be transposed to their own research.

A Nucleophilic Gold(III) Carbene Complex

The first AuIII carbene complex was prepared by reacting a geminal dianion with a (P,C) cyclometalated AuIII precursor. Its structure and bonding situation have been thoroughly investigated by experimental and computational means. The presence of a high-energy highest occupied molecular orbital (HOMO) centered at the carbene center suggests nucleophilic character for the AuIII carbene complex. This unprecedented feature was confirmed by reactions with two electrophiles (PhNCS and CS2 ), resulting in two types of C=C coupling reactions.

Synthesis and Reactivity of an End-Deck cyclo-P4 Iron Complex

Reduction of the FeII complex [(Ph PP2Cy )FeCl2 ] (2) generated an electron-rich and unsaturated Fe0 species, which was reacted with white phosphorus. The resulting new complex, [(Ph PP2Cy )Fe(η4 -P4 )] (3), is the first iron cyclo-P4 complex and the only known stable end-deck cyclo-P4 complex outside Group V. Complex 3 features an FeII center, as shown by Mössbauer spectroscopy, associated to a P42- fragment. The distinct reactivity of complex 3 was rationalized by analysis of the molecular orbitals. Reaction of complex 3 with H+ afforded the unstable complex [(Ph PP2Cy )Fe(η4 -P4 )(H)]+ (4), whereas with CuCl and BCF, the complexes [(Ph PP2Cy )Fe(η4 :η1 -P4 )(μ-CuCl)]2 (5) and [(Ph PP2Cy )Fe(η4 :η1 -P4 )B(C6 F5 )3 ] (6) were formed.

Mechanistic Investigations of the Synthesis of Size‐Tunable Ni Nanoparticles by Reduction of Simple NiII Diamide Precursors

Herein, we present a detailed study of the conversion of a nickel(II) diamide precursor to size-tunable, monodisperse nickel nanoparticles (NPs). The thermal decomposition of nickel(II) dioleylamide, synthesized either independently or in situ, resulted in the formation of Ni NPs without the coproduction of water. Mechanistic studies were conducted on the stability and reduction pathway of the NiII precursor, and on the consequent particle formation. Variations in the ratio of trioctylphosine (TOP) to nickel allowed size tunability, which resulted in nanoparticles that ranged in size from 4 to 11 nm in diameter. The DFT calculations support a mechanistic pathway that involves nickel reduction by imine formation. This water-free method was extended to the synthesis of water-sensitive M0 NPs (M=Fe, Co).

Setting P-Donor Ligands into Context: An Application of the Ligand Knowledge Base (LKB) Approach

GRAPHICAL ABSTRACT Abstract The properties of 13 monodentate P-donor ligands not previously characterized in the Ligand Knowledge Base (LKB) approach have been determined computationally, allowing their addition to the LKB-P map of ligand space.1 Consideration of ligand positions and close neighbors in ligand space can help to establish a chemical context and hence guide their application to organometallic catalysis. Here we demonstrate this potential application of the LKB-P map and discuss known and likely applications of these ligands.

Water-free synthesis of monodisperse Nickel(0) nanoparticles

Nickel nanoparticles (Ni NPs) are valued for a variety of applications. ranging from catalysis1 to magnetic properties2 to the development of more complex nanomaterials.3 The morphology of these nanoparticles plays a huge role in their behavior. Their size. shape. crystallinity, and surface state greatly affect their properties. and consequently their behavior in practical applications.4.5 Previously. our lab developed a method for synthesizing size-tunable. monodisperse Ni NPs through the reduction of Ni(acac) 2 (acac = acetylacetonate) at high temperature by oleylamine. An associated mechanistic study revealed that water was formed by the dehydration of the acac ligands during the reaction (Scheme 1).6

The role of water in the synthesis of indium nanoparticles

We report the water-assisted synthesis of indium nanoparticles (In NPs). We found that a precise amount of water was necessary to allow the formation of the desired 7 nm In NPs: the oxidation of the In surface by water inhibits the growth of NPs as well as subsequent reactivity with white phosphorus (P4). A novel surface activation method based on the use of organosilanes is presented.

CCDC 276879: Experimental Crystal Structure Determination

Related Article: P.Adkine, T.Cantat, E.Deschamps, L.Ricard, N.Mezailles, P.Le Floch, M.Geoffroy|2006|Phys.Chem.Chem.Phys.(PCCP)|8|862|doi:10.1039/b513736p