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A series of neutral [RhX(nbd)(κC-MeIm∩Z)] and cationic [Rh(nbd)(κ2C,N-MeIm∩Z)]+ (X = Cl, Br; MeIm = 3-methylimidazol-2-yliden-1-yl; ∩Z = N-functionalized wingtip; nbd = 2,5-norbornadiene) complexes featuring NHC ligands functionalized with a 1-aminopropyl, 3-dimethylaminopropyl, pyridin-2-ylmethyl, or quinolin-8-ylmethyl substituent have been prepared. These complexes efficiently catalyze the polymerization of phenylacetylene without base as a co-catalyst affording stereoregular polyphenylacetylenes of very high molar mass. Polymers of Mw up to 2 × 106 g mol−1 and moderate dispersity have been prepared with neutral chloro-complexes having aminopropyl wingtips. Catalyst precursors bearing functionalized NHC ligands with a flexible amino-alkyl wingtip are significantly more active than those having a heterocyclic substituent. These complexes are in general much more active than related compounds having N-functionalized phosphine ligands. Polymer characterization by SEC/MALS/DRI analysis has revealed the presence of a fraction of branched polymer of high molar mass in most samples obtained with catalysts having N-heterocyclic substituents at the NHC ligand. The N-donor function at the NHC ligand likely behaves as an internal base for the deprotonation of phenylacetylene to give the initiating alkynyl cationic [Rh(nbd)(C[triple bond, length as m-dash]C-Ph)(κC-MeIm∩ZH)]+ species. However, the participation of neutral alkynyl species [Rh(nbd)(C[triple bond, length as m-dash]C-Ph)(κC-MeIm∩Z)] should be considered in order to rationalize the notable catalytic activity of some neutral chloro-complexes., The authors express their appreciation for the financial support from the Spanish Ministerio de Ciencia e Innovación, MCIN/AEI/10.13039/501100011033, under the project PID2019-103965GB-I00, and the “Departamento de Ciencia, Universidad y Sociedad del Conocimiento del Gobierno de Aragón” (group E42_20R).

The [Rh(μ-Cl)(IPr)(η2-coe)]2/pyridine system efficiently catalyzes the polyhydrothiolation of a series of dialkynes with dithiols, producing sulfur-rich poly(vinylidene sulfide)s with a typical Mw in the range 20.000–124.000 and vinylidene content of 75–87%. A combination of flexible aliphatic dithiols, including 1,6-hexanedithiol and 2,2′-(ethylendioxy)diethanethiol, and the rigid aromatic dithiol 4,4′-thiobisbenzenethiol, with rigid aromatic dialkynes, 1,3-diethynylbenzene and 1,4-diethynylbenzene, and flexible dialkynes, including propargyl ether and 1,7-octadiyne, have been used to prepare poly(vinylidene sulfide)s. The copolymerization of flexible dithiols with rigid aromatic dialkynes or vice versa results in high molecular weight polymers, Mw up to 259.000, with low polydispersities. However, polyhidrothiolation of flexible dialkynes with flexible dithiols is much less efficient and usually results in the formation of oligomers. The interplay of the IPr and pyridine ligands on the RhCl(IPr)(py)(η2-coe) catalyst, which controls the regioselectivity of the alkyne insertion step towards the branched vinyl sulfide, is key in the preparation of these poly(vinylidene sulfide)s.

This article belongs to the Special Issue Recent Advances in Ophthalmic Drug Delivery., Intravitreal injection is the gold standard therapeutic option for posterior segment pathologies, and long-lasting release is necessary to avoid reinjections. There is no effective intravitreal treatment for glaucoma or other optic neuropathies in daily practice, nor is there a non-invasive method to monitor drug levels in the vitreous. Here we show that a glaucoma treatment combining a hypotensive and neuroprotective intravitreal formulation (IF) of brimonidine–Laponite (BRI/LAP) can be monitored non-invasively using vitreoretinal interface imaging captured with optical coherence tomography (OCT) over 24 weeks of follow-up. Qualitative and quantitative characterisation was achieved by analysing the changes in vitreous (VIT) signal intensity, expressed as a ratio of retinal pigment epithelium (RPE) intensity. Vitreous hyperreflective aggregates mixed in the vitreous and tended to settle on the retinal surface. Relative intensity and aggregate size progressively decreased over 24 weeks in treated rat eyes as the BRI/LAP IF degraded. VIT/RPE relative intensity and total aggregate area correlated with brimonidine levels measured in the eye. The OCT-derived VIT/RPE relative intensity may be a useful and objective marker for non-invasive monitoring of BRI/LAP IF., This study was supported by Carlos III Health Institute, (grants numbers: M17/00213, PI17/01726, PI17/01946), and by MINECO/AEI/ERDF, EU (grants numbers: MAT2017-83858-C2-2).

Intravitreal administration is widely used in ophthalmological practice to maintain therapeutic drug levels near the neuroretina and because drug delivery systems are necessary to avoid reinjections and sight-threatening side effects. However, currently there is no intravitreal treatment for glaucoma. The brimonidine-LAPONITE® formulation was created with the aim of treating glaucoma for extended periods with a single intravitreal injection. Glaucoma was induced by producing ocular hypertension in two rat cohorts: [BRI-LAP] and [non-bri], with and without treatment, respectively. Eyes treated with brimonidine-LAPONITE® showed lower ocular pressure levels up to week 8 (p < 0.001), functional neuroprotection explored by scotopic and photopic negative response electroretinography (p = 0.042), and structural protection of the retina, retinal nerve fibre layer and ganglion cell layer (p = 0.038), especially on the superior-inferior axis explored by optical coherence tomography, which was corroborated by a higher retinal ganglion cell count (p = 0.040) using immunohistochemistry (Brn3a antibody) up to the end of the study (week 24). Furthermore, delayed neuroprotection was detected in the contralateral eye. Brimonidine was detected in treated rat eyes for up to 6 months. Brimonidine-LAPONITE® seems to be a potential sustained-delivery intravitreal drug for glaucoma treatment., This paper was supported by the Rio Hortega Research Grant M17/00213, PI17/01726, PI17/01946 (Instituto de Salud Carlos III), and by MAT2017-83858-C2-2 MINECO/AEI/ERDF, EU.

Infection of orthopedic devices is a major complication in the postsurgical period generating important health issues and economic consequences. Prevention strategies could be based on local release of antibiotics from the orthopedic device itself to avoid adhesion and growth of bacteria. The purpose of this work is to demonstrate the efficiency to prevent these infections by a cefazolin-eluting, perforated stainless steel implant in an in vivo ovine model. The device was placed in the tibia of sheep, one group receiving cefazolin-loaded implants whereas the control group received empty implants. All implants were experimentally infected by direct inoculation of Staphylococcus aureus ATCC 6538. In vitro cytotoxicological studies were also performed to check the effect of antibiotic on cell viability, integrity, and cycle. Results showed that sheep receiving cefazolin-loaded devices were able to avoid implant-associated infections, with normal tissue healing process. The antibiotic release followed a local concentric pattern as demonstrated by high-performance liquid chromatography detection in tissues. The in vitro results indicate the lack of relevant cytotoxic effects for the maximum antibiotic concentration released by the device. These results demonstrate the efficiency and safety of cefazolin-eluting implants in an ovine model to prevent early postsurgical infections of orthopedic devices. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1976-1986, 2018.

Laponite clay is able to retain dexamethasone by simple physisorption, presumably accomplished by hydrogen bonding formation and/or complexation with sodium counterions, as shown by solid state NMR. The physisorption can be somehow modulated by changing the solvent in the adsorption process. This simple system is able to deliver dexamethasone in a controlled manner to solutions used as models for vitreous humor. The proven biocompatibility of laponite as well as its transparency in the gel state, together with the simplicity of the preparation method, makes this system suitable for future in vivo tests of ophthalmic treatment., This study was supported by the Instituto de Salud Carlos III (project PI12/02285) and authors would like to acknowledge the financial support received from Diputación General de Aragón (E11 Group co-financed by the European Regional Development Funds).

This paper presents a novel nanoformulation for sustained-release delivery of dexamethasone (DEX) to the ocular posterior segment using a Laponite (LAP) carrier—DEX/LAP 1:10 w w−1 formulation; 10 mg ml−1. In vivo ocular feasibility and pharmacokinetics after intravitreal (IV) and suprachoroidal (SC) administration in rabbit eyes are compared against IV administration of a DEX solution (1 mg ml−1). Thirty rabbit eyes were injected with the DEX/LAP formulation (15 suprachoroid/15 intravitreous). Ophthalmological signs were monitored at day 1 and at weeks 1–4–12–24 post-administration. Three eyes per sample time point were used to quantify DEX concentration using high-performance liquid chromatography-mass spectrometry. The ocular tissues' pharmacokinetic parameters (lens, vitreous humour, choroid-retina unit and sclera) were studied. DEX/LAP was well tolerated under both administration methods. Peak intraocular DEX levels from the DEX/LAP were detected in the vitreous humour after both deliveries soon after administration. The vitreous area under the curve was significantly greater after both DEX/LAP deliveries (IV: 205 968.47; SC: 11 442.22 ng g−1 d−1) than after IV administration of the DEX solution (317.17 ng g−1 d−1). Intravitreal DEX/LAP delivery extended higher vitreous DEX levels up to week 24 (466.32 ± 311.15 ng g−1). With SC delivery, DEX levels were detectable in the choroid-retina unit (12.04 ± 20.85 ng g−1) and sclera (25.46 ± 44.09 ng g−1) up to week 24. This study demonstrated the intraocular feasibility of both SC and IV administration of the DEX/LAP formulation. The LAP increased the intraocular retention time of DEX when compared with conventional solutions. DEX/LAP could be considered a biocompatible and useful sustained-release formulation for treating posterior-pole eye diseases., This paper was supported by the Carlos III Health Institute (Programme Grant PI12/02285), by Rio Hortega Research Grant M17/00213, PI17/01726, PI17/01946 (Carlos III Health Institute), by MAT2017-83858-C2-2 MINECO/AEI/FEDER, EU, and by the Regional Government of Aragon (E37_17R group, co-financed under FEDER 2014–2020 'Construyendo Europa desde Aragón').

Dinuclear phosphine-amido, [Rh(diene){μ-NH(CH)PPh}], and cationic phosphine-amino complexes, [Rh(diene){PhP(CH)NHR}] (diene = cod, nbd, tfb) and [Rh{PhP(CH)NHR}], have been prepared from the corresponding amino-functionalized phosphines PhP(CH)NHR (R = H, Me) and suitable rhodium(I) precursors. The dinuclear [Rh(diene){μ-NH(CH)PPh}] complexes bearing π-acceptors diene ligands such as nbd or tfb exhibit a remarkable catalytic activity in phenylacetylene (PA) polymerization affording stereoregular polyphenylacetylenes with, unlike the cod precursor, unimodal molar mass distributions of very high molecular weights, M up to ≈ 1.2 × 10, and moderate polydispersity indexes. These complexes are more active than the mononuclear phosphino-anilido [Rh(diene){PhP(CH)NMe}] complexes, which are in turn more active than the cationic complexes [Rh(diene){PhP(CH)NHMe}], [Rh(nbd){PhP(CH)NH}], and [Rh(nbd){PhP(CH)NHMe}] bearing the same diene ligand. In contrast, complexes [Rh{PhP(CH)NHR}] (R = H, Me) without a diene ligand have been found to be inactive in PA polymerization. The excellent catalytic performance of [Rh(diene){μ-NH(CH)PPh}] (diene = nbd, tfb) complexes is a consequence of the mode of activation of PA that likely results in the formation of unsaturated alkynyl species [Rh(diene)(CC-Ph)L] (L = PA, THF), which may be competent for PA polymerization., Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) under the Projects CTQ2013-42532-P and CTQ2016-75884-P and the Diputación General de Aragón (DGA/E42_17R) is gratefully acknowledged.

[Purpose]: To study the safety and biocompatibility of Laponite clay (LAP) within an intravitreal and suprachoroidal administration in rabbit eyes., [Methods]: Thirty-two New Zealand albino rabbits were divided into two experimental groups to test intravitreal (IVT group) and suprachoroidal (SCS group) administration of a 100-μl and 50-μl Laponite suspension respectively. Following injection, the eyes were monitored by ocular tonometry, slit-lamp eye examination and indirect ophthalmoscopy, at 24 h, 1, 4, 12, and 14 weeks post administration. Histological examination was also performed to determine whether any ocular pathological change had occurred. Throughout the study, LAP presence in vitreous was estimated by complexometric titration with ethylenediaminetetraacetic acid (EDTA), taking advantage of the Laponite high content of magnesium ions., [Results]: Neither significant differences in the intraocular pressure, nor relevant ocular complications were found in the two experimental groups after LAP administration. The histology of the retina remained unchanged. LAP presence in vitreous could be indirectly confirmed by complexometric titration until 14 weeks post administration in eyes of IVT group., [Conclusion]: Laponite could be considered as a vehicle for potential clinical use in ocular drug administration, due to its proven ocular biocompatibility and its transparency in gel state., This study has received financial support from the following institutions: Instituto de Salud Carlos III (grant PI12/02285), and Diputación General de Aragón (E11 Group co-financed by the European Regional Development Funds).

Complex RhCl(IPr)(pyridine)(η2-coe) (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) efficiently catalyzes the polyhydrothiolation of aromatic diynes with aliphatic dithiols to give vinylidene-based polymers (vinylidene content of 80%) with high molecular weights (Mw up to 199 000). These polymers have been shown to be chemically modifiable through hydrogenation and chemical oxidation processes., This research was supported by the Ministerio de Economía y Competitividad (MINECO/FEDER) under the Project CTQ2016-75884-P and the Diputación General de Aragón (DGA/FSE-E07). A. D. G. also thanks MINECO for the postdoctoral grant Juan de la Cierva-Incorporación 2015 (IJCI-2015-27029).

Infection of orthopedic devices is a major complication in the postsurgical period generating important health issues and economic consequences. Prevention strategies could be based on local release of antibiotics from the orthopedic device itself to avoid adhesion and growth of bacteria. The purpose of this work is to demonstrate the efficiency to prevent these infections by a cefazolin-eluting, perforated stainless steel implant in an in vivo ovine model. The device was placed in the tibia of sheep, one group receiving cefazolin-loaded implants whereas the control group received empty implants. All implants were experimentally infected by direct inoculation of Staphylococcus aureus ATCC 6538. In vitro cytotoxicological studies were also performed to check the effect of antibiotic on cell viability, integrity, and cycle. Results showed that sheep receiving cefazolin-loaded devices were able to avoid implant-associated infections, with normal tissue healing process. The antibiotic release followed a local concentric pattern as demonstrated by high-performance liquid chromatography detection in tissues. The in vitro results indicate the lack of relevant cytotoxic effects for the maximum antibiotic concentration released by the device. These results demonstrate the efficiency and safety of cefazolin-eluting implants in an ovine model to prevent early postsurgical infections of orthopedic devices. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1976-1986, 2018.

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence., The new rhodium(i) complexes [Rh(Cl)(COD)(R-NHC-(CH2) 3Si(OiPr3)3)] (R=2,6-diisopropylphenyl (2a); n-butyl (2b)) have been synthesised and fully characterised. The study of their application as ketone hydrosilylation catalysts showed a clear N-substituent effect, 2a being the most active catalyst precursor. Complex 2a has been immobilised in the mesoporous materials MCM-41 and KIT-6. The new hybrid materials have been fully characterised and used as catalyst precursors for the preparation of poly(silyl ether)s by catalytic hydrosilylation. The heterogeneous catalytic systems based on the materials 2a-MCM-41 and 2a-KIT-6 afford polymers with high average molecular weight (Mw) Mw = 2.61 × 106 g mol-1 (2a-MCM-41) and Mw = 4.43 × 105 g mol-1 (2a-KIT-6). © 2014 The Royal Society of Chemistry., Financial support from the Spanish “Ministerio de Economia y Competividad” projects, CONSOLIDER INGENIO CSD2006-0015 and CSD2009-00050, CTQ2011-27593 and CTQ2012-35665, “Juan de la Cierva” program (M. I.) and “Diputación General de Aragón-Fondo Social Europeo” group E07 is acknowledged., We would like to thank the Unit of Information Resources for Research (URICI-CSIC) for their support to publish this work in open format.

Ancient molecular typing depends on DNA survival in archaeological bones. Finding valuable tools to predict DNA presence in ancient samples, which can be measured prior to undertaking a genetic study, has become an important issue as a consequence of the peculiarities of archaeological samples. Since the survival of DNA is explained by complex interrelations of multiple variables, the aim of the present study was to analyze morphological, structural, chemical, and biological aspects of a set of medieval human bones, to provide an accurate reflection of the state of preservation of the bony components and to relate it with DNA presence. Archaeological bones that yielded amplifiable DNA presented high collagen content (generally more than 12%), low racemization values of aspartic acid (lesser than 0.08), leucine and glutamic acid, low infrared splitting factor, small size of crystallite, and more compact appearance of bone in the scanning electron micrographs. Whether these patterns are characteristic of ancient bones or specific of each burial site or specimen requires further investigation.

[Purpose]: To develop a simple, specific, and rapid method to determine corticosteroid concentrations in vitreous humor. [Methods]: An analytical method based on high-pressure liquid chromatography-tandem mass spectrometry (HPLC-MS) with a simple extraction procedure was developed. New Zealand albino rabbits (n = 54) received a single (0.1 mL) intravitreal injection of dexamethasone (DXM, 0.1 mg), methylprednisolone (MP, 2 mg), or triamcinolone acetonide (TA, 10 mg). Eyes were enucleated and mean vitreous steroid levels were quantified at 12 h and 1, 2, 3, 7, and 14 days. [Results]: Corticosteroids were extracted from the vitreous with acetonitrile, and TA was extracted with ethyl acetate, yielding high protein precipitation and clean solution samples. Vitreous samples were analyzed by isocratic HPLC-MS with mobile phase comprising acetonitrile and 2 mM ammonium formate buffer in water, pH 3.5. The linear range was 50–100,000 ng/g with a lower quantification limit of 45 ng/g for DXM and MP, and 50 ng/g for TA. Vitreous levels of DXM and MP were not detectable 14 days post-administration. Vitreous levels of TA were positive and stable throughout the study in both injected and control eyes. [Conclusions]: The HPLC-MS analytical method is an alternative to HPLC-MS/MS methods, sensitive enough for identifying and quantifying steroids in vitreous humor at a therapeutic dosage scale.

JDF-L1 is a microporous titanosilicate exhibiting a layer structure with pore size of about 3 Å. It is consequently an attractive material to separate H2-containing mixtures. This is the reason why JDF-L1, after disaggregation by means of hexadecyltrimethylammonium surfactant, has been combined with a carboxyl group containing copolyimide (6FDA-4MPD/6FDA-DABA 4:1) to produce mixed matrix membranes, which were applied to the separation of H2/CH4 and O2/N2 mixtures. Additionally, due to the sheet growth habit of JDF-L1 crystals, a preferential horizontal orientation of the JDF-L1 filler particles dispersed into the polymer was expected. This preferential orientation, which was achieved when the polymer solution concentration used during the membrane casting process was relatively low, has been studied by optical and electronic microscopy, X-ray diffraction and polarized Raman spectroscopy. A quantitative analysis was carried out applying Cussler's model for mixedmatrixmembranes with oriented flakes., We gratefully thank the German Academic Exchange Service (DAAD) for the financial support within the budget of the project related person exchange program (PPP, 0804142). Also, financial support from the Spanish Science and Innovation Ministry (MAT2007-61028, CIT-420000-2009-32, and HD2008-0001) and the Aragon Government (PI035/09) is gratefully acknowledged.

Chiral ordered mesoporous silica (COMS) was synthesized in basic media by combining tetraethyl orthosilicate and quaternized aminosilane (with a templating role) silica sources together with four different standard amino acids (arginine, histidine, isoleucine, and proline). Besides the hexagonal MCM-41-type structure, narrow pore size distribution, and high specific surface area, it was found that these solids have potential for enantiomeric separation because of the transference of chirality from the amino acid to the silica. This is illustrated by the resolution of several racemic mixtures (those of proline, isoleucine, trans-4-hydroxyproline, pipecolic acid, valine, leucine, and phenylglycine) with the calcined COMS prepared with l-proline. The opposite behavior observed in induced circular dichroism experiments with calcined COMS, obtained using both enantiomers of proline, confirmed their chiral nature. The high number and variety of existing amino acids, and chiral organic compounds in general, makes these ordered silicas attractive for the production of enantiopure substances.(Figure Presented) © 2011 American Chemical Society., Financial support from the Spanish Ministry of Science and Innovation (MAT2007-61028) is gratefully acknowledged. C.C. also acknowledges a “Juan de la Cierva” grant from the Spanish Science and Innovation Ministry

Titanium centers grafted on hydrophobic silica bearing long chain silanes (octadecyl or octyl) are able to oxidize dibenzothiophene (DBT), as well as simpler sulfides and 2,6-dimethyldibenzothiophene, to the corresponding sulfone in hydrocarbon solution with aqueous hydrogen peroxide in only a slight excess over the stoichiometric amount, without using any surfactant or cosolvent. The productivity per gram of catalyst or per Ti site can be optimized by tuning the silanization of the silica (or using a commercially available silanized silica) and the Ti loading of the catalyst. The catalyst preparation and the oxidation reaction are compatible with the use of an industrial grade aromatic solvent., The financial support of the Ministerio de Economía y Competitividad (INNPACTO program, IPT-310000-2010-021, and project CTQ2011-28124), Peroxychem Spain S.L. (former FMC-Foret S.A.), and the Diputación General de Aragón (E11 Group co-financed by the European Regional Development Funds) is gratefully acknowledged.

The number of Sisingle bondOsingle bondTi bonds in silica-supported titanium catalysts is an important parameter that affects activity and selectivity. Although comparisons between different catalysts can be made by infrared spectroscopy, estimation of the contribution of the different species is a difficult task. UV spectroscopy has been used to characterize three different titanium–silsesquioxane complexes. The wavelength in solution is highly dependent on the concentration, and broad bands are obtained by DRUV, at wavelengths that correlate with the number of Sisingle bondOsingle bondTi bonds. The deconvolution of the DRUV spectra of silica-supported titanium catalysts allows identification of the three types of tetrahedral (pentacoordinated) species, together with octahedral species. These results correlate well with the known silanol densities of the different silica supports, and the catalytic activity and selectivity for epoxidation are clearly favored by the reduction in octahedral titanium and the increase in the number of tripodal species., This work was made possible by the generous financial support of the CICYT (Project PPQ2002-04012) and the Diputación General de Aragón.

The results of activity and selectivity in the epoxidation of cyclohexene with dilute hydrogen peroxide can be improved by careful optimization of the catalyst properties and the reaction conditions. The type of silica support, the silanization with long hydrocarbon chains and mainly the slow addition of hydrogen peroxide are important factors. This slow addition not only noticeably improves the selectivity in terms of epoxidation products but also leads to a better recoverability of the catalyst, showing the role of the radical pathway in deactivation and titanium leaching. In the best case the catalyst can be reused at least three times with very low titanium leaching, and an overall productivity of 228 mmol epoxidation products per mmol Ti., This work was made possible by the generous financial support of the C.I.C.Y.T. (Project PPQ2002-04012). Kenrich Petrochemicals Inc. is gratefully acknowledged for the generous gift of KR TTS.

Correction for `Preparation and characterization of activated montmorillonite clay supported 11-molybdo-vanado-phosphoric acid for cyclohexene oxidation' by S. Boudjema et al., RSC Adv., 2015, 5, 6853-6863.

Theoretical calculations demonstrate that the presence of ligands with different basicity modifies the Lewis acidity (expressed both as the LUMO energy and the enthalpy of coordination of a NH3 molecule) of the active centers in silica-supported titanium catalysts. Several catalysts containing different organic ligands bonded to the titanium centers have been prepared, characterized, and tested in the benchmark reaction of cyclohexene with hydrogen peroxide. Both the activity and the selectivities of the catalysts depend on the relative basicity of the ligands and their variation is proportional to the calculated Lewis acidity, expressed as the LUMO energy. With more basic ligands, hydrolysis of the epoxide to diol occurs to a lesser extent at the expense of the catalytic activity and the epoxidation/allylic oxidation selectivity, showing the coincidence of the active sites for epoxidation and hydrolysis reactions.

The combination of chiral preparative HPLC separation, VCD measurements, and theoretical calculations allows the unambiguous determination of the absolute configuration of the conformationally flexible products of copper-catalyzed carbene insertion reactions. DFT calculations were used to predict the stereochemical outcome of the copper-bis(oxazoline)-catalyzed C-H insertion reaction between methyl diazophenylacetate and tetrahydrofuran and also to predict the absolute configuration of the major stereoisomers derived from the same reaction with different cyclic ethers. These predictions were verified experimentally through NMR and VCD spectroscopy and allowed rationalization of the stereochemical outcome of these reactions without further derivatization of the products, which can be prblematic under certain conditions as described herein. © 2013 American Chemical Society., This work was made possible by the generous financial support of the Ministerio de Economía y Competitividad (MINECO, Project CTQ2011-28124).

7 páginas, 10 figuras, 2 tablas., AM-4 is a layered porous titanosilicate built from TiO6 and SiO4 polyhedra. An improved synthesis of AM-4 crystalsenabling control of particle size by secondary growth and reducing synthesis time is presented. A new material, UZAR-S2, has been obtained by exfoliation of the smaller AM-4. The exfoliation consists of proton exchange with acetic acid, intercalation with nonylamine, and final activation by washing with HCl/water/ethanol. Besides XRD, TEM, N2 adsorption, FTIR, and UV/Vis characterization highlighting the delaminated character of UZAR-S2, CO2 adsorption was also measured., Financing from the Spanish Ministry of Science and Innovation (MAT2007-61028, CIT-420000-2009-32) and the Government of Aragón (PI035/09) is gratefully acknowledged. C. C. also thanks the Ministry for the “Juan de la Cierva” programme.

Characterization of poly(phenylacetylene) (PPA) samples produced using Rh(I) complexes featuring hemilabile phosphine ligands by size exclusion chromatography, multiangle light scattering (SEC-MALS), or asymmetric flow field flow fractionation (A4F)-MALS has revealed that some of these PPA samples contain a mixture of linear and branched polymer. The occurrence and extent of branching is dependent on both catalyst structure and polymerization conditions. The levels of branching are consistent with either terminal branching through copolymerization of macromonomer or chain transfer to polymer, where the branched species are less reactive toward further polymerization than the linear chains. The MM dependence of B, the number of branches per molecule, or λ, the number of branches per 1000 repeat units, suggests that the latter explanation may be correct, but further work is needed. © 2010 American Chemical Society., The financial support from Ministerio de Ciencia e Innovación (MICINN/FEDER) is gratefully acknowledged (Projects CTQ2009-08089 and CTQ2009-10132). M.A. and M.I.B. are thankful for graduate research fellowships provided by Instituto Universitario de Catálisis Homogénea (IUCH). S.C. acknowledges the support of the Fundación Aragonesa de Investigación y Desarrollo (ARAID) and IUCH.

A series of cationic complexes [Rh(diene){Ph2P(CH 2)nZ}][BF4] (diene = 1,5-cyclooctadiene (cod), tetrafluorobenzobarralene (tfb) or 2,5-norbonadiene (nbd)) containing functionalized phosphine ligands of the type Ph2P(CH 2)nZ (n = 2, or 3; Z = OMe, NMe2, SMe) have been prepared and characterized. These complexes have shown a great catalytic activity for phenylacetylene (PA) polymerization. Catalyst screening and optimization have determined the superior performance of complexes containing a P,Nfunctionalyzed phosphine ligand, [Rh(diene){Ph2P(CH 2)3NMe2}][BF4] (diene = cod, 5; tfb, 6; nbd, 7), and tetrahydrofuran as solvent. The influence of the diene ligand and the effect of temperature, PA to rhodium molar ratio, addition of water or a cocatalyst, DMAP (4-(dimethylamino)pyridine), have been studied. Diene ligands strongly influence the catalytic activity and complexes 6 and 7 are far more active than 5. Both complexes gave poly(phenylacetylene) (PPA) with very high number-average molecular weights (Mn) of 970000 (6) and 1420000 (7). The addition of DMAP resulted in a dramatic drop in the PPA molecular weight, 106 000 (6) and 233 000 (7). The PPA obtained with the system 6/DMAP showed a narrow molecular weight distribution (MwMn = 1.20) and incremental monomer addition experiments have demonstrated the quasi-living nature of the polymerization reaction under these conditions. The PPA obtained with these catalytic systems has been characterized by 1H and 13C(1H) NMR spectroscopy and shows a cis-transoidal configuration with a high level of steroregularity (cis content superior to 99%). TGA, DSC, and IR analysis have revealed a thermal cis↔ trans isomerization process at 150̈C. The mechanism of PA polymerization has been investigated by spectroscopic means, under stoichiometric and catalytic conditions, and shows an active role of the hemilabile phosphine ligand both in the initiation and, probably, in the termination steps through proton transfer processes involving the hemilabile fragment of the ligand. © 2009 American Chemical Society., The financial support from Ministerio de Educación y Ciencia (MEC/FEDER) is gratefully acknowledged (Project CTQ2006-03973/BQU). MIB thanks a graduate research fellowship.

Siloxane bridges on the silica surface react with HCl leading to a more hydrophilic solid, which surprisingly shows a better performance as support for titanium centres than the parent silica. The use of a weaker electrophilic species, such as an acyl chloride, allows the modulation of the support properties in such a way that it can be prepared the best silica-supported titanium catalyst for epoxidation with diluted hydrogen peroxide. This result demonstrates that the hydrophobic character of the solid is not a sine qua non requirement to obtain efficient epoxidation catalysts. Although the reasons for this good behaviour are not fully understood, it seems that the type of surface titanium species is the key factor, and modifications of silanol density with the different treatments control the distribution of titanium species., This work was made possible by the generous financial support of the C.I.C.Y.T. (project PPQ2002-04012) and the Diputación General de Aragón.

Silica-supported titanium catalysts are active in the epoxidation of cyclohexene with diluted hydrogen peroxide at 80°C. At low H2O2/Ti ratio the contribution of the direct mechanism of epoxidation is important, around 40% of the productive H2O2 conversion and 60% of the epoxidation reaction. However, the increase in H2O2/Ti ratio modifies these results. The contribution of the direct epoxidation to H2O2 conversion is reduced to 20–30%, whereas contribution to epoxidation is kept in the range 40–60%. Neither the silanization of the silica surface nor the substitution of the isopropoxy groups by tartaric acid improves the behavior of the solid in these conditions. However, the simultaneous variation in hydrophilic character of the surface and titanium environment increases the contribution of the direct epoxidation. In contrast, the increase in H2O2/Ti ratio reduces the epoxide hydrolysis. The catalysts lose some titanium after reaction, but in general they show higher stability than closely related solids. The activity for direct and radical contributions changes after recovering, showing the important change in nature of the catalytic sites, which are not easily regenerated by extensive washing with different solvents. In any case, with cyclooctene, an alkene that does not form radicals, the activity for direct epoxidation shows a decline in every recycling but final turnover numbers are similar in the first three runs, showing high stability of the titanium on the solid., This work was made possible by the generous financial support of the C.I.C.Y.T. (Project MAT99-1176)

MCM-41 can be used in the same way as amorphous silica for the preparation of supported titanium catalysts; MCM-41 does not show clear advantages over silica in epoxidation reactions with either TBHP or H2O2; only in one case is a positive effect observed and this involves the recycled catalyst with H2O2., This work was made possible by the generous financial support of the CICYT (project MAT99-1176).

Titanium tetraisopropoxide supported on silica [Si–Ti(OiPr)] is an efficient catalyst for the epoxidation of alkenes, cyclooctene, and cyclohexene with 30% hydrogen peroxide at 80°C. In the case of cyclohexene, allylic oxidation is also produced through a radical mechanism and the epoxide undergoes hydrolysis to the trans-diol due to the acidity of the catalyst and the presence of water. The catalyst can be recycled with very low titanium leaching and has a slightly lower catalytic activity after two cycles. These best results are obtained when an alkene/H2O2 ratio=20 is used. Lowering this ratio up to 5 has a detrimental effect on the final yield but does not affect the epoxidation/allylic selectivity. Further decrease to alkene/H2O2=1 leads to very low activity and selectivity. This catalyst bears isopropoxy groups that can be substituted by nonfunctionalized and functionalized diols. Such a process modifies the activity and selectivity of the catalyst, showing that it is possible to modulate the performance of this kind of titanium catalyst by changing the environment of the catalytic sites. The substitution with ethylene glycol improves the performance of the recovered catalyst. The catalyst prepared by treating the original Si–Ti(OiPr) with tartaric acid [Si–Ti(TA)] gives rise to high overall oxidation yields, with 97% selectivity in H2O2 and an epoxidation/allylic oxidation ratio around 65/35. Moreover, it is very stable during at least three cycles. End-capping of the silica surface has a positive effect on the epoxide hydrolysis but not on the epoxidation/allylic oxidation selectivity, in contrast with previously described results. The lower functionalization of the silylated solids noticeably increases the turnover numbers. Filtration experiments in the reaction conditions have shown that Si–Ti(OiPr) and Si(ec)–Ti(TA) are truly heterogeneous catalysts, with no contribution of the leached species. However, Si–Ti(TA) leads to leaching of active species, although an important part of them remains on the solid after three filtrations, and the contribution to the activity of homogeneous and heterogeneous species is nearly the same., This work was made possible by the generous financial support of the CICYT (Project MAT96-1053).