Exploring the surface organometallic chemistry on silica of highly electrophilic yttrium complexes is a relatively uncommon endeavor, particularly when focusing on tris-alkyl complexes characterized by Y-C sigma-alkyl bonds. A drawback with this class of complexes once grafted on silica, is the frequent occurrence of alkyl transfer by ring opening of siloxane groups, resulting in a mixture of species. Herein, we employed a more stable homoleptic yttrium allyl complex bearing bulky eta(3)-1,3-bis(trimethylsilyl)allyl ligand to limit this transfer reaction. This strategy has been validated by comparing the reactivity between [Y{ eta(3)-1,3-C3H3(SiMe3)(2)}(3)] and [Y(o-CH2PhNMe2)(3)] with SiO2-700, where the undesired alkyl transfer reaction occurred for [Y(o-CH2PhNMe2)(3)] leading to a bipodal [(equivalent to SiO)(2)Y(o-CH2PhNMe2)] as major surface species, 2, while [Y{ eta (3)-1,3-C3H3(SiMe3)(2)}(3)] resulted selectively in a monopodal species, [(equivalent to SiO)Y{eta(3)-1,3-C3H3(SiMe3)(2)}(2)], 1. The materials obtained were characterized by DRIFT, solid state NMR, mass balance analysis and EXAFS. Catalyst 1 showed high activity compared to 2 in ethylene polymerization. The catalytic performance of this neutral catalyst 1 was extended to pre-industrial scale in the presence of hydrogen and 1-hexene. An unprecedented activity, up to 7400 g(PE) g(cat)(-1) h(-1) was obtained even with very low concentration of scavenger AliBu(3) (TIBA/Y=1.2). The obtained HDPE exhibited desired spherical particle morphology with broad molar mass distribution.

The conversion of methyl oleate by cross-metathesis with ethylene using readily accessible supported group VI oxo species was addressed. TON up to 500 and 5000 were achieved using bisgrafted tungsten- and molybdenum based systems, respectively ( SiO)(2)M(=O)R-2 (M = W, R = CH2SiMe3, M = Mo, R = CH2CMe3). In the case of molybdenum, these results are comparable to those obtained by Mo-based systems in homogeneous catalysis. Optimization studies showed that ethylene pressure plays a major role in these systems, with inhibition at high pressure resulting from degenerated metathesis involving ethylene and alpha-olefins.

Crosslinked polymer particles carrying hemilabile bis-N,N-aminophosphine (PNP) moieties are obtained by the copolymerization of a PNP-derived monomer bearing four vinyl fragments as cross-linkers, with para-tert-butylstyrene and divinylbenzene, using free radical copolymerization in presence of AIBN, performed in aqueous dispersed medium. This new support was characterized by thermogravimetric analysis, elemental analysis, laser diffraction, solid state NMR. The PNP moiety could allow monochelation to palladium. The resulting insoluble Pd-catalyst revealed to be very active for Suzuki cross-coupling with several substrates, allowing separation of the product from the catalyst by filtration. The final palladium PS-PNP catalyst could be reused for several catalytic cycles.

2,3-dimethylbutane is selectively converted into 2,3-dimethylbutenes at 500 degrees C under hydrogen or at 390 degrees C under nitrogen in the presence of bimetallic catalysts Pt-Sn/Li-Al2O3. The high stability of the catalyst along the reaction is obtained by selective modification of the Pt/Li-Al2O3 catalyst using Surface Organometallic Chemistry (SOMC).

A well-defined bis-oxo bisiloxy tungsten surface species has been prepared by a new synthetic non-aqueous approach. The reaction of [W(O =)((OBu)-Bu-t)(4)] with the silica surface dehydroxylated at 200 degrees C proceeds by W-O cleavage with concomitant (BuOH)-Bu-t release, leading to bigrafted [( SiO)(2)W(= O)((OBu)-Bu-t)(2)]. Upon heating at 300 degrees C, it converts into the bis-oxo derivative [( SiO)(2)W(= O)(2)]. Without co-catalyst, this material demonstrated high, sustained activity and selectivity in propene metathesis. This emphasizes the importance of the design of robust bis-oxo catalysts by Surface Organometallic Chemistry and represents a significant step to understand and mimic the active species of the industrial WO3/SiO2 system.

The novel complex W (=O)Np3F has been prepared by fluorination of the corresponding chloride counterpart with AgBF4. The reactivity of this complex with silica dehydroxylated at 700 degrees C afforded a well-defined silica supported monopodal tungsten oxo trialkyl surface species ( SiO)W (=O)Np-3. The reaction proceeds both through silanolysis of the W-F bond and opening of a siloxane bridge, with formation of a Si-F fragment, thanks to the affinity of silicon for fluoride. The resulting surface species was characterized by elemental analysis, DRIFT, solid state NMR and EXAFS spectroscopy. This material presenting fluorine on its surface shows an enhanced catalytic activity in propylene self-metathesis compared to its monopodal counterpart ( SiO)W (=O)Np-3 (prepared from W (=O)Np3Cl) suggesting that the Si-F in a close vicinity to the W decreases the electron density of the W and thus increases its reactivity towards the olefinic substrate. (C) 2018 Published by Elsevier B.V.

Well-defined bifunctional supported catalysts that comprise tungsten hydride moieties and Bronsted acid sites were prepared successfully. The catalysts showed outstanding activities and selectivities toward the formation of high-value-added products, 2,3-dimethylbutenes and 3,3-dimethylbutene, through a combination of the metathesis and dimerization of isobutene. The relationship between the physicochemical properties of the catalysts and their activities and selectivities indicated that isobutene conversion increased from 4 to 95% as a function of the silica content of the silicated alumina (obtained from Sasol). Nevertheless, the selectivity toward branched hexenes showed a volcano-shaped curve that presented a maximum for the catalyst with 5 wt% silica. Therefore, the control of the support acidity by the silica loading on alumina resulted in an increase of the selectivity toward neohexene.

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.

Iron chelators, through their capacity to modulate the iron concentration in cells, are promising molecules for cancer chemotherapy. Chelators with high lipophilicity easily enter into cells and deplete the iron intracellular pool. Consequently, iron-dependent enzymes, such as ribonucleotide reductase, which is over-expressed in cancer cells, become nonfunctional. A series of calix[4]arene derivatives substituted at the lower rim by ICL670, a strong FeIII chelator, have been synthesized. Physicochemical properties and antiproliferative, angiogenesis, and tumorigenesis effects of two calix[4]arenes mono- (5a) or disubstituted (5b) with ICL670 have been studied. These compounds form metal complexes in a ratio of one to two ligands per FeIII atom as shown by combined analyses of the protometric titration curves and ESIMS spectra. The grafting of an ICL670 group on a calix[4]arene core does not significantly alter the acid-base properties, but improves the iron-chelating and lipophilicity properties. The best antiproliferative and anti-angiogenic results were obtained with calix[4]arene ligand 5a, which possesses the highest corresponding properties. Analyses of molecular dynamics simulations performed on the two calix[4]arenes provide three-dimensional structures of the complexes and proved 5a to be the most stable upon complexation.

The development of selective electrochemical iron sensor is still a challenging task. One promising possibility is to use organically functionalized inorganic particles, for instance silica, as sensitive element. Herein, we report on the design and synthesis of calix[4]arene-based platforms modified with ICL670 iron chelator and alkylamino chain(s). These new molecular edifices could be easily grafted on silica particles. The strategy relies on selective calix[4]arenes functionalizations by alkylamino chains at the lower rim, in partial-cone or 1,3-alternate conformations. The different synthesis routes are presented and discussed.

Cell cycle progression is dependent on the intracellular iron level, and chelators lead to iron depletion and decrease cell proliferation. This antiproliferative effect can be inhibited by exogenous iron. In this work, we present the synthesis of new synthetic calix[4]arene podands bearing alkyl acid and alkyl ester groups at the lower rim, designed as potential iron chelators. We report their effect on cell proliferation, in comparison with the new oral chelator ICL670 (4-[3,5-bis-(2-hydroxyphenyl)-1,2,4-triazol-1-yl]-benzoic acid). The antiproliferative effect of these new compounds was studied in human hepatocarcinoma HepaRG cell cultures using the MTT assay. Their cytotoxicity was evaluated by extracellular LDH activity. Preliminary results indicate that their antiproliferative effect is due to their cytotoxicity. The efficiency of these compounds, comparable to that of ICL670, was independent of iron depletion. This effect remains to be further explored. Moreover, it also shows that novel substituted calix[4]arenes could open the way to new valuable medicinal chemistry scaffolding.</.

A new eco-efficient and environmentally friendly palladium/copper catalytic procedure for the C3-alkenylation of free NH-indoles is reported. Using homogeneous or heterogeneous heterobimetallic [Pd/Cu]-catalysts under mild reaction conditions (10mol% Pd-catalyst and 10mol% Cu-catalyst, 70°C, air), substituted indoles are fully (58–82% isolated yields) and selectively (75–100% selectivity) converted to the expected 2-substituted-3-vinylindoles.

A simple palladium catalysed procedure for the synthesis of 1,2- and 2,3-disubstituted indoles is reported. It was found that the selectivity of the reaction, i.e. the N1- versus the C3-arylation of 2-functional indoles was mainly directed by electronic factors. Fine tuning of the reaction conditions and the right choice of the substrates allowed a full selective N1-(ArI, [Pd(OAc)2], PPh3) or C3 (ArBr, [Pd(OAc)2], AgBF4) arylation. Using only 1mol% Pd-catalyst gave up to 92% isolated yield of expected compound.

A new palladium/copper catalytic procedure for the C3-alkenylation of free NH-indoles is reported. Using homogeneous or heterogeneous hetero-bimetallic [Pd/Cu]-catalysts under mild reaction conditions (10mol% Pd-catalyst and 10mol% Cu-catalyst, 70°C, air), substituted indoles are fully (58–82% isolated yields) and selectively (75–100% selectivity) converted to the expected 2-substituted-3-vinyl indoles.