Marc Birot

Inorganic monoliths hierarchically textured via concentrated direct emulsion and micellar templatesElectronic supplementary information (ESI) available: XRD profiles, nitrogen physisorption data and pore size distribution calculated from density functional theory, for the xSi-HIPE0.035 series. See http://www.rsc.org/suppdata/jm/b4/b400984c/

Hierarchical inorganic porous monoliths have been prepared using concentrated emulsion and micellar templates. The texture of these monoliths has to be tuned varying either the pH of the continuous aqueous phase, the emulsification process or the oil volumic fraction. These materials show interconnected macroporosity associated with vermicular-type mesostructuration. They possess an average mesoporosity of 800 m2 g−1 associated with bulk density as low as 0.08 g cm−3, which is comparable to values obtained for silica aerogel.

Regio- and stereoselective addition of sterically hindered silylboranes to terminal alkynes

Abstract Novel stable organosilylboranes possessing dimesityl groups attached to boron were synthesised. They gave an addition reaction with terminal acetylenic hydrocarbons in the presence of a transition metal complex. Thus, (diphenylmethylsilyl)dimesitylborane and (diphenyl-tert-butylsilyl)dimesitylborane reacted in good yields with phenylacetylene and alk-1-ynes in the presence of Pd2(dba)3(etpo)2 as a catalyst. The structures of the products were determined by NMR spectroscopy using INEPT techniques coupled to computational simulation. Various heteronuclear coupling constants J 13 C − H and J 29 Si − H were determined for the first time in this series. The results showed that the dimesitylboryl group added to the terminal acetylenic carbon atom and the organosilyl group to the internal carbon atom, according to a regio- and stereoselective syn-addition.

One-step regiospecific synthesis of allylic silanes - extension to benzylsilanes

Abstract Allyltrichlorosilanes are prepared according to a one-step regiospecific process based on the reaction of allyl chlorides with SiCl 4 and NiCp 2 /HMPA (catalyst), in the presence of industrial methylchlorodisilane fraction. 4 Benzyltrihalosilanes are similarly obtained.

Macrocellular Pd@ionic liquid@organo-Si(HIPE) heterogeneous catalysts and their use for Heck coupling reactions

Supported ionic liquid phases (SILPs) within macrocellular silica-based foams are prepared by a simple impregnation in organic solvents. Thin ionic liquid layers with thicknesses of 6 to 12 nm were obtained. The SILs mobility has been evidenced through NMR solid state spectroscopy. Subsequently, palladium salts are efficiently trapped within the SILPs, while an in situ palladium hydrogenation allowed an efficient reduction and formation of 10 nm diameter palladium metal nanoparticles. These hybrid foams are used as heterogeneous macrocellular catalysts for the Heck coupling reaction of iodobenzene and cyclohexyl acrylate, where palladium leaching appears to be very low. Despite recyclability minimized through the entrapment of detrimental ammonium salts within the macroporous network during the reaction, competitive TONs and TOFs were reached, while separation of the products can be reached at ease, due to the fact that both palladium species and by-products are trapped within the monolithic foams.

Synthesis and characterization of new precursors to nearly stoichiometric SiC ceramics: Part II A homopolymer route

Organosilicon polymers with a (C/Si (atomic ratio)<1.28) exhibiting Si–Si and Si–CH2–Si linkages in their backbone have been prepared and characterized by multinuclear magnetic resonance and infrared spectroscopies, size exclusion chromatography and thermogravimetric analysis. These precursors give SiC ceramics with a C/Si (atomic ratio)≈1.14 and a relatively low oxygen content (between 1.5–3 at %).

Synthesis of new poly(2,4-disilapentane) oligomers via dehydrocondensation reaction using Group IV metallocene catalysts

Abstract Polycondensation of 2,4-disilapentane in the presence of titanium or zirconium-based catalysts afforded original poly(2,4-disilapanentane) oligomers useful as ceramic precursors.

SYNTHESIS AND CHEMICAL PROPERTIES OF 1,3-DICHLORO-1,3-DIHYDRIDODISILAZANES

Abstract A trans-silylation route to 1,3-dichloro-l,3-dihydridodisilazanes, a novel class of polyfunctional disilazane, is described. Thus, heating hexamethyl- or heptamethyl-disilazane under reflux in the presence of an excess of dichlorohydrogenosilane R 1 SiHCl 2 , led to compounds of formula (R 1 ClHSi) 2 NR 2 (R 1 = Me, Et, Vi or Ph and R 2 = H; R 1 = Me and R 2 = Me) in high yield. The exchange of chlorinated organosilicon moieties was strongly facilited by a catalytic amount of ( π Bu 4 N)F. Interpretation of the results and a few chemical properties of these novel disilazanes are reported.

Détermination de structures au moyen de la RMNn du 29Si: Transfert sélectif de population avec les méthylchlorodisilylméthanes

Abstract The selective population transfer (SPT) technique has been applied to 29 Si NMR of the complete series of methylchlorodisilylmethanes, several of which are new compounds. A great enhancement of the signals was observed and unambiguous assignments based on the determination of 2 J (SiH) coupling constants could be made. The first example of this type is presented.

Tough silicon carbide macro/mesocellular crack-free monolithic foams

Taking the benefit of Si(HIPE) as a hard monolithic template to shape macro-mesoporous foams by using polycarbosilane as pre-ceramic precursor β-SiC, macro/mesocellular foams have been synthesized. Both macroscopic Plateau border morphology and final mechanical properties can be tuned through varying the starting amount of polycarbosilane precursor. Resulting silicon carbide foams, labeled SiC(HIPE), are composed of β-SiC at the microscopic length scale, while bearing 110 m2 g−1 as specific area at the mesoscopic length scale, and up to 92% of macroporosity. The as-synthesized crack-free SiC(HIPE) monolithic foams are associated with outstanding mechanical properties as, for instance, 50–58 MPa of compression Young modulus. The thermal behaviors of these foams are assessed with bulk heat capacities comprising between 0.15 J g−1 K−1 to 0.55 J g−1 K−1 that decrease when the foam porosity increases, while their heat conductivities are following the same rules ranging from 2.6 to 4.6 W m−1 K−1.

Nano-spots induced break of the chemical inertness of boron: a new route toward reversible hydrogen storage applications

Novel LiBH4–metal-loaded carbonaceous foams have been designed to trigger reversible hydrogen storage properties. The metallic nanoparticles favour preferential wetting of LiBH4 on their surface and subsequent nucleation and growth, a configuration in which borate formation is strongly minimized. A cooperative effect between lower boron oxidation and the presence of metallic particles bearing intrinsic high heat capacity (acting as high temperature nanospots) promotes a strong improvement toward the rehydrogenation process, where the chemical inertness of boron has been overcome in this way for the first time. Hence, the LiBH4–M@C-HIPE(25HF) hybrid macrocellular foams (with M = Pd or Au) facilitate a reversible hydrogen storage process with a remnant capacity of about 7.4 wt% H2 (related to LiBH4) after 5 desorption–absorption ) hybrid…” and throughout the article should “absorption” be changed to “adsorption”??>cycles.