Joël J. E. Moreau

Hybrid materials: versatile matrices for supporting homogeneous catalysts

Hybrid materials are increasingly used for supporting homogeneous catalysts. This review describes the various methodologies used to synthesize such hybrid materials or to graft catalysts on inorganic or hybrid supports. Applications of these materials for reactions mediated by supported organometallic or organic catalysts are presented.

Asymmetric synthesis at silicon : I. Hydrosilylation of carbonyl compounds catalysed by a chiral phosphine—rhodium complex: Stereochemistry and mechanism☆

Abstract Hydrosilylation of carbonyl compounds catalysed by rhodium complexes III accompanied by retention of configuration at the silicon atom. Optically active alkoxysilanes of up to 46% optical purity are obtained using prochiral silanes and an asymmetric catalyst. The hydrosilylation of prochiral ketones leads to an asymmetric reaction at both the silicon and carbon centres with different optical yields. A mechanism is proposed to explain the stereochemical results.

Advanced selective optical sensors based on periodically organized mesoporous hybrid silica thin films.

Mesoporous thin films functionalized with silylated [small beta]-diketone compounds with symmetry mesostructure dependent on the probe quantity were used as fast uranyl species sensors with high selectivity and sensitivity.

THE DESIGN OF SELECTIVE CATALYSTS FROM HYBRID SILICA-BASED MATERIALS

Abstract The sol–gel processing of appropriated molecular precursors easily leads to a variety of mixed materials. Silica-based organic–inorganic hybrids constitute a very versatile class of solids. Their preparation in a controlled way can lead to materials with intrinsic properties. This paper will concentrate on the potential uses of hybrids for the preparation of catalytic materials by design. It offers unique possibilities (i) to obtain dispersed metal species or particles on oxide supports; (ii) to control the pore structure of the catalytic material; and (iii) to prepare new hybrid supports with selective properties.

Reactions de l'ortho-bis(dimethylsilyl)benzene avec les nitriles catalysees par des complexes du rhodium

Abstract The silylation reaction of nitriles using a bis-hydrosilane has been studied. The reaction of 1,2-bis(dimethylsilyl)benzene in the presence of [RhCl(PPh 3 ) 3 ] as catalyst leads to a mixture of trans - N , N -disilylated enamines and N , N -disilylated amines, the ratio depending on the nitrile and on the catalyst. The enamine is selectively obtained from arylacetonitriles. A possible pathway is proposed to explain the formation of these products. The reaction of bis-hydrosilanes with N , N -diethylphenylacetamide catalyzed by [RhCl(PPh 3 ) 3 ] lead to an enamine by deoxygenation of the amide.

Chiral organic–inorganic solids as enantioselective catalytic materials

New enantioselective catalytic materials result from the sol–gel hydrolysis condensation of silyl-substituted chiral diamine–rhodium complexes.

Nanostructuring organo-silicas: combination of intermolecular interactions and molecular recognition properties to generate self-assembled hybrids with phenylene or adenine⋯thymine bridging units

Owing to hydrophobic interactions, silyl linkers containing long alkylene chains allowed the synthesis of self-organised hybrids. Lamellar organo-silicas with phenylene or a hydrogen-bonded adenine⋯thymine complex as the bridging units are reported.

Alcoolyse selective d'organosilanes catalysee par un complexe du rhodium☆

Abstract Chlorotris(triphenylphosphine)rhodium is a very effective and selective catalyst for the alcoholysis of diarylsilanes. Treatment with ethylenic alcohols leads in one step to 1-oxa-2-silacycloalcane. The alcoholysis of asymmetric organosilicon compounds proceeds predominantly with retention of configuration at the silicon atom. A mechanism is proposed to explain the experimental results.

Periodic mesoporous organosilica containing ionic bis-aryl-imidazolium entities: Heterogeneous precursors for silica-hybrid-supported NHC complexes

The synthesis of periodic mesoporous organosilica incorporating ionic diarylimidazolium species was achieved by hydrolysis–polycondensation of a bis-silylated diarylimidazolium (Si-IMes-) precursor in the presence of non-ionic triblock copolymer as structure directing agents. Although hydrolysis polycondensation of the pure precursor gave materials with moderate porosity, highly porous solids were obtained by the addition of tetraethoxysilane (TEOS) to the sol solution. The architecture of the materials on a mesoscopic scale strongly depends on the TEOS/Si-IMes ratio in the sol. Materials with highly regular hexagonal symmetry were obtained using high molar excess of TEOS. The obtained PMO type materials incorporating diarylimidazolium substructures are promising heterogeneous precursors for the formation of silica hybrid supported N-heterocyclic carbene complexes and therefore have great potential in heterogeneous catalysis.

Novel silica-based hybrid materials incorporating binaphthyl units: a chiral matrix effect in heterogeneous asymmetric catalysis

Abstract Polysilsesquioxane hybrid materials containing chiral binaphthyl moieties are readily available by coupling (R)- or (S)-2,2′-dihydroxy-1,1′-binaphthyl (BINOL) with 3-(triethoxysilyl)propyl isocyanate and subsequent hydrolysis polycondensation of the resulting bis-trialkoxysilylated carbamate precursor. Rhodium species were embedded in the chiral hybrid matrix. The catalytic properties of the solids were evaluated in hydride-transfer reduction to prochiral ketones. When the catalytic species were embedded in an entirely chiral network, enantiomeric excesses up to 45% were observed.