Fabien Massicot

First direct evidence of size-dependent structural transition in nanosized nickel particles

Abstract Finely dispersed Ni powders were obtained after chemical reduction of Ni(II) salts by activated sodium hydride in organic solvents. This process allows one to prepare particles in the nanometre range. The particles with sizes smaller than 4nm were found to be hcp whereas larger particles were fcc. To the best of our knowledge, this is the first observation that unsupported Ni powder may crystallize in the hcp system and that the phase stability of this metallic element is particle size dependent.

Synergistic Effect in Bimetallic Ni–Al Clusters. Application to Efficient Catalytic Reductive Dehalogenation of Polychlorinated Arenes

Abstract Subnanometric Ni–Al clusters, in situ prepared by reduction of equimolar amounts of Ni(OAc) 2 and Al(Acac) 3 induced by alkoxide activated sodium hydride, exhibit a high catalytic activity for efficient reductive dehalogenation of aliphatic and aromatic halides and polychlorinated arenes.

An efficient route to biaryls from aryl halides catalysed by subnanometrical 2,2′-bipyridine liganded Ni–Al clusters

Abstract It has been shown that the new 2,2′-bipyridine liganded Ni–Al bimetallic clusters are efficient in promoting the catalytic homocoupling of (het)aryl chlorides and bromides.

Enantiopure Quaternary α-Trifluoromethyl-α-alkoxyaldehydes from L-Tartaric Acid Derived Ketoamides

The diastereoselective nucleophilic trifluoromethylation of a range of ketoamides derived from L-tartaric acid has been studied. TMSCF3 in the presence of a catalytic amount of K2CO3 in DMF has been identified as the conditions leading to the highest diastereoselectivities. A sequential one-pot reaction trifluoromethylation-etherification of the trifluoromethylcarbinol has been developed. Only one further one-pot reaction, ketal hydrolysis-oxidative cleavage, led to the final alpha-trifluoromethylated alpha-alkoxyaldehydes. This procedure was applied to the preparation of a series of enantiopure aryl, heteroaryl, and alkyl alpha-trifluoromethyl-alpha-alkoxyaldehydes.

Copper(II) complexes with lactamides: solution and solid state studies

Three functionalized ligands, S(−)-N-(pyridin-2-ylmethyl)lactamide (pml), S(−)-N-(2-dimethylaminoethyl)lactamide (dmael) and S(−)-N-(3-dimethylaminopropyl)lactamide (dmapl), were synthesized by the aminolysis of S(−)-methyl lactate with the corresponding primary amines. Their protonation constants and the stability constants of the chelates formed with copper(II) were determined by potentiometry. In all cases, we detected the formation of CuLH−1+, CuLH−2 and CuLH−3− species (L = free ligand). The copper(II) complexes prepared in the solid state were characterized by IR and UV-visible spectroscopies. The crystal structure of [Cu(pmlH−1)X] (X = Cl, Br) shows that copper(II) is bound to the pyridyl and the deprotonated amidic nitrogen atoms, as well as to the oxygen atom of the hydroxyl group, which leads to a mono-chelated compound. The geometry around Cu2+ is square pyramidal.

Generation of ε,ε-difluorinated metal-pentadienyl species through lanthanide-mediated C-F activation

Heavy metal on Lewis acid: The combination of lanthanide metals and AlCl3 has been employed for selective single C-F activation in benzofulvenes comprising an exocyclic CF3 substituent. Intermediate ϵ,ϵ-difluorinated metal-dienyl species react with a large variety of aldehydes in a highly regio- and diastereoselective fashion to afford 1,1-disubstituted indenes bearing a difluorovinyl group. These new building blocks have been further transformed through a hydrogenation-cyclization process into fluorinated heterocyclic spiro compounds.

The Role of the Counterion and of Silicon Chelation in the Selective Mono(trifluoromethylation) of Tartaric Acid Derived 1,4-Diketones

The addition of trifluoromethyl(trimethyl)silane (TFMTMS) to tartaric acid derived aromatic 1,4-diketones was reported to be highly stereoselective but also chemoselective towards a monoaddition product. This chemoselectivity remained unexplained. Complementary experiments and monitoring of the reaction by electrospray ionization mass spectrometry (ESI-MS) show that: i) the countercation (tetrabutylammonium (TBA(+)) or Cs(+)) associated to the initiator and the charged intermediates in the chain reaction plays a crucial role and ii) in the case of a tetrabutylammonium salt initiator, the second addition on the preformed monoadduct does occur but the resulting bis(trifluoromethyl)carbinolate is unable to evolve through the chain-transfer process and it exhibits an intramolecular Si-O interaction.

Synthesis and properties of nearly single-shell nickel clusters in amorphous aluminium oxides

Abstract We introduce a new method for the synthesis of Al-Ni nanosized particles. After partial oxidation, this technique is able to produce ultrafine sub-nanometric nickel clusters dispersed with an amorphous aluminium oxide. Such clusters consist of about 15 nickel atoms which exhibit discrete electronic energy levels and superparamagnetism. A very significant enhancement of the catalytic properties is observed. We expect that division of metals down to such a reduced scale will lead us to new properties and to a technological breakthrough since upscaling this method to industrial production rate is straightforward.

(+)-Camphor-mediated kinetic resolution of allylalanes: a strategy towards enantio-enriched cyclohex-2-en-1-ylalane

An efficient (+)-camphor-mediated kinetic resolution of racemic cyclohex-2-en-1-ylalane is described. This approach provides an enantiomerically enriched form of the alane, in situ available for synthetic uses. Applied to the allylation of aldehydes, this protocol leads to the corresponding homoallylalcohols in a highly enantioselective manner.

Lithium Hydride Mediated Nickel(0) Catalysed Biaryl Synthesis from Aryl Chlorides and Bromides

Lithium hydride is efficiently used as a reducing agent in the ligated Ni0 catalysed homocoupling of aryl bromides and chlorides.