Enantioselective synthesis of tungsten trimetallic cluster chalcogenides

Excision of {W3Q7Br4}n (Q = S, Se) of polymeric phases using chiral diphosphines is a general procedure to synthesize optically pure trinuclear clusters. Chiral transfer from the enantiomerically pure diphosphines (+)-1,2-bis[2,5-(dimethylphospholan-1-yl)]ethane, (R,R)-Me-BPE, (−)-1,2-bis[2,5-(dimethylphospholan-1-yl)]ethane, (S,S)-Me-BPE, and (−)-1,2-bis[2,5-(dimethylphospholan-1-yl)]benzene, (R,R)-DUPHOS, to the inorganic phase affords enantiopure P-[W3S4Br3((R,R)-Me-BPE)3]+, M-[W3S4Br3((S,S)-Me-BPE)3]+ (M-1+), P-[W3Se4Br3((R,R)-Me-BPE)3]+ (P-2+) and P-[W3S4Br3((R,R)-DUPHOS)3]+ (P-3+) clusters. The central W3(μ3-Q)(μ-Q) unit defines an incomplete cuboidal core with the capping chalcogen lying on a threefold axis and an effective C3 symmetry. Symbols P- and M- are used to indicate the rotation of the bromine atoms around the C3 axis, with the chalcogen atom pointing towards the viewer. Invariably, P-W3Q4 complexes are obtained starting from (R,R)-diphosphines, while its M-W3Q4 enantiomer is isolated in the presence of (S,S)-diphosphines. All complexes have been structurally characterized by single crystal X-ray diffraction and their enantiomeric character confirmed by CD spectroscopy.The financial support of the Spanish Ministerio de Economia y Competitividad (Grants CTQ2011-23157), Universitat Jaume I (research project P1.1B2013-19) and Generalitat Valenciana (Prometeo/2009/053 and ACOMP/2013/215) is gratefully acknowledged. The authors also thank the Serveis Central d’Instrumentació Cientifica (SCIC) of the Universitat Jaume I for providing us with the mass spectrometry, NMR, circular dichroism and X-ray facilities

Hexanuclear Niobium Cluster Compounds with Protonated N‐Base Cations

Octahedral clusters of the [M6X12] type offer numerous possibilities to form structural arrangements through different choices of bonding situations. In this paper a series of new cluster compounds of the transition metal niobium is described, which consist of the [Nb6Cl18]2–, and in one case [Nb6Cl18]3–, anion and protonated N‐base cations ([MIm‐H]+, [nPr3N‐H]+, [TMGu‐H]+, and [Tzn‐H]+). They all are prepared using water scavenger compounds [SOCl2 or (Ac)2O] under oxidising conditions, resulting in two‐electron (or one‐electron, respectively) oxidized cluster units with respect to the starting material [Nb6Cl14(H2O)4]·4H2O. Of five members of this group single‐crystal X‐ray structures were determined. The cluster anions exist in all structures as discrete units. The acidic H atoms of all N‐bases are hydrogen bonded to H acceptors, in 4 cases to outer, exo bonded Cl atoms of the cluster unit and in one case to the O atom of a co‐crystallized THF molecule. In [TMGu‐H]2[Nb6Cl18] chains of cluster anions exist hydrogen‐bonded through bridging [TMGu‐H]+ cations. ESI mass spectra of [MIm‐H]2[Nb6Cl18]·2SOCl2 and [TMGu‐H]2[Nb6Cl18] show the expected isotopic distribution patterns for the anions together with other peaks associated to chloride mass losses and/or reduction processes

Efficient and Selective N‐Methylation of Nitroarenes under Mild Reaction Conditions

Herein, we report a straightforward protocol for the preparation of N,N‐dimethylated amines from readily available nitro starting materials using formic acid as a renewable C1 source and silanes as reducing agents. This tandem process is efficiently accomplished in the presence of a cubane‐type Mo3PtS4 catalyst. For the preparation of the novel [Mo3Pt(PPh3)S4Cl3(dmen)3]+ (3+) (dmen: N,N′‐dimethylethylenediamine) compound we have followed a [3+1] building block strategy starting from the trinuclear [Mo3S4Cl3(dmen)3]+ (1+) and Pt(PPh3)4 (2) complexes. The heterobimetallic 3+ cation preserves the main structural features of its 1+ cluster precursor. Interestingly, this catalytic protocol operates at room temperature with high chemoselectivity when the 3+ catalyst co‐exists with its trinuclear 1+ precursor. N‐heterocyclic arenes, double bonds, ketones, cyanides and ester functional groups are well retained after N‐methylation of the corresponding functionalized nitroarenes. In addition, benzylic‐type as well as aliphatic nitro compounds can also be methylated following this protocol

Identification and characterization of a novel cathinone derivative 1-(2,3dihydro-1H-inden-5-yl)-2-phenyl-2-(pyrrolidin-1-yl)-ethanone seized by customs in Jersey

A suspicious white powder labeled “idanyl-biphenyl-amninone,” which was seized by customs officials at the "channel island" of Jersey, UK, was brought to our laboratory for identification and characterization of its structure. The elucidation process required the use of several complementary analytical techniques, including gas chromatography–mass spectrometry, liquid chromatography coupled with high-resolution mass spectrometry, nuclear magnetic resonance spectroscopy, and X-ray crystallography. The unknown compound was ultimately identified as 1-(2,3-dihydro-1H-inden-5-yl)-2-phenyl-2-(pyrrolidin-1-yl)-ethanone, a novel cathinone derivative. To the best of our knowledge, this compound has not been registered in the CAS or IUPAC databases. However, it has recently been marketed on the Internet as “indapyrophenidone,” and we therefore propose this as the common name of the compound. The results of this study may serve forensic and clinical laboratories in the identification of its related compounds with similar backbone structure using the information reported in this article obtained by the application of advanced analytical techniques. It may also lead to timely and effective response on the part of legislators and law enforcement

Updating the list of known opioids through identification and characterization of the new opioid derivative 3,4-dichloro-N- (2-(diethylamino)cyclohexyl)-N- methylbenzamide (U-49900)

New psychoactive substances have been rapidly growing in popularity in the drug market as non-illegal drugs. In the last few years, an increment has been reported on the use of synthetic alternatives to heroin, the synthetic opioids. Based on the information provided by the European Monitoring Centre for Drug and Drug Addiction, these synthetic opioids have been related to overdoses and deaths in Europe and North America. One of these opioids is the U-47700. A few months ago, U-47700 was scheduled in the U.S. and other countries, and other opioid derivatives have been appearing in order to replace it. One of these compounds is U-49900, an analog of U-47700. A white powder sample was obtained from an anonymous user in Spain. After an accurate characterization by gas chromatography-mass spectrometry, ultra-high performance liquid chromatography-high resolution mass spectrometry, nuclear magnetic resonance and single-crystal X-ray diffraction; and complemented by Fourier-transformed infrared spectroscopy, ultraviolet and circular dichroism spectrophotometry, the drug sample was unequivocally identified as U-49900. The information provided will be useful for the Early Warning System and forensic laboratories for future identifications of the U-49900, as well as in tentative identifications of other related opioids

Healthy novel gluten-free formulations based on beans, carob fruit and rice: Extrusion effect on organic acids, tocopherols, phenolic compounds and bioactivity

Rice and legumes have great potential in the development of novel gluten-free snacks that are healthier than traditional snacks. Novel gluten-free extruded foods (composed of rice: 50–80%, beans: 20–40% and carob: 5–10%) were analysed and the extrusion effects regarding organic acids, tocopherols, phenolic compounds and bioactive properties were evaluated. The total concentration of organic acids was not significantly affected by extrusion, while tocopherols showed a significant reduction. Extrusion did not produce an increase of the total phenolic content. For the bioactivity assays, commercial extruded rice, carob and most of the extruded samples showed anti-proliferative activity, which was higher than in the non-extruded samples, while for the anti-inflammatory activity, the extrusion process did not show a significant effect. Regarding the antimicrobial activity, low potential was observed with extruded and non-extruded samples showing high values of MIC and MBC as the microorganisms tested were multi-resistant isolated clinical strains.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Program PT2020 for financial support to CIMO (UID/AGR/00690/2019), L. Barros and R. Calhelha contracts. The authors are also grateful to FEDER-Interreg España-Portugal programme for financial support through the project 0377_Iberphenol_6_E, to the Spanish Ministry of Economy and Competitiveness (Project RTA2012-00042-C02) and INIA for the financial support of C. Arribas.info:eu-repo/semantics/publishedVersio

Catalytic Hydrogenation of Azobenzene in the Presence of a Cuboidal Mo3S4 Cluster via an Uncommon Sulfur-Based H2 Activation Mechanism

Azobenzene hydrogenation is catalyzed under moderate conditions by a cuboidal Mo3(μ3-S)(μ-S)3 diamino complex via a cluster catalysis mechanism. Dihydrogen activation by the molecular [Mo3(μ3-S)(μ-S)3Cl3(dmen)3]+ cluster cation takes place at the μ-S bridging atoms without direct participation of the metals in clear contrast with classical concepts. The reaction occurs with the formation of 1,2-diphenylhydrazine as an intermediate with similar appearance and disappearance rate constants. On the basis of DFT calculations, a mechanism is proposed in which formation of 1,2-diphenylhydrazine and aniline occurs through two interconnected catalytic cycles that share a common reaction step that involves H2 addition to two of the bridging sulfur atoms of the catalyst to form a dithiolate Mo3(μ3-S)(μ-SH)2)(μ-S) adduct. Both catalytic cycles have similar activation barriers, in agreement with the experimental observation of close rate constant values. Microkinetic modeling of the process leads to computed concentration–time profiles in excellent agreement with the experimental ones providing additional support to the calculated reaction mechanism. Slight modifications on the experimental conditions of the catalytic protocol in combination with theoretical calculations discard a direct participation of the metal on the reaction mechanism. The effect of the ancillary ligands on the catalytic activity of the cluster fully agrees with the present mechanistic proposal. The results herein demonstrate the capability of molybdenum sulfide materials to activate hydrogen through an uncommon sulfur based mechanism opening attractive possibilities toward their applications as catalysts in other hydrogenation processes

Base-Free Catalytic Hydrogen Production from Formic Acid Mediated by a Cubane-Type Mo3S4 Cluster Hydride

Formic acid (FA) dehydrogenation is an attractive process in the implementation of a hydrogen economy. To make this process greener and less costly, the interest nowadays is moving toward non-noble metal catalysts and additive-free protocols. Efficient protocols using earth abundant first row transition metals, mostly iron, have been developed, but other metals, such as molybdenum, remain practically unexplored. Herein, we present the transformation of FA to form H2 and CO2 through a cluster catalysis mechanism mediated by a cuboidal [Mo3S4H3(dmpe)3]+ hydride cluster in the absence of base or any other additive. Our catalyst has proved to be more active and selective than the other molybdenum compounds reported to date for this purpose. Kinetic studies, reaction monitoring, and isolation of the [Mo3S4(OCHO)3(dmpe)3]+ formate reaction intermediate, in combination with DFT calculations, have allowed us to formulate an unambiguous mechanism of FA dehydrogenation. Kinetic studies indicate that the reaction at temperatures up to 60 °C ends at the triformate complex and occurs in a single kinetic step, which can be interpreted in terms of statistical kinetics at the three metal centers. The process starts with the formation of a dihydrogen-bonded species with Mo–H···HOOCH bonds, detected by NMR techniques, followed by hydrogen release and formate coordination. Whereas this process is favored at temperatures up to 60 °C, the subsequent β-hydride elimination that allows for the CO2 release and closes the catalytic cycle is only completed at higher temperatures. The cycle also operates starting from the [Mo3S4(OCHO)3(dmpe)3]+ formate intermediate, again with preservation of the cluster integrity, which adds our proposal to the list of the infrequent cluster catalysis reaction mechanisms.Funding for open access charge: CRUE-Universitat Jaume

Selective Dehydrogenation of Formic Acid Catalyzed by Air-Stable Cuboidal PN Molybdenum Sulfide Clusters

Formic acid is considered as a promising hydrogen storage material in the context of a green hydrogen economy. In this work, we present a series of aminophosphino and imidazolylamino Mo3S4 cuboidal clusters which are active and selective for formic acid dehydrogenation (FAD). Best results are obtained with the new [Mo3S4Cl3(ediprp)3](BPh4) (4(BPh4)) (ediprp=(2-(diisopropylphosphino)ethylamine)) cluster, which is prepared through a simple ligand exchange process from the Mo3S4Cl4(PPh3)3(H2O)2 precursor. Under the conditions investigated, complex 4+ showed significantly improved performance (TOF=4048 h−1 and 3743 h−1 at 120 °C in propylene carbonate using N,N-dimethyloctylamine as base after 10 min and 15 min, respectively) compared to the other reported molybdenum compounds. Mechanistic investigations based on stoichiometric and catalytic experiments show that cluster 4+ reacts with formic acid in the presence of a base to form formate substituted species [Mo3S4Cl3-x(OCOH)x(ediprp)3]+ (x=1–3) from which the catalytic cycle starts. Subsequently, formate decarboxylation of the partially substituted [Mo3S4Cl3-x(OCOH)x(ediprp)3]+ (x=1, 2, 3) catalyst through a β-hydride transfer to the metal generates the trinuclear Mo3S4 cluster hydride. Dehydrogenation takes place through protonation by HCOOH to form Mo−H⋅⋅⋅HCOOH dihydrogen adducts, with regeneration of the Mo3S4 formate cluster. This proposal has been validated by DFT calculations.Funding for open access charge: CRUE-Universitat Jaume

Spatiotemporal monitoring of selected pathogens in Iberian ibex (Capra pyrenaica)

An epidemiological surveillance programme was carried out to assess exposure and spatiotemporal patterns of selected pathogens (Brucella spp., Mycobacterium avium subsp. paratuberculosis (MAP), Mycoplasma agalactiae, Pestivirus and bluetongue virus (BTV)) in Iberian ibex (Capra pyrenaica) from Andalusia (southern Spain), the region with the largest population of this species. A total of 602 animals in five distribution areas were sampled during 2010–2012 (P1) and 2013–2015 (P2). The Rose Bengal test (RBT) and complement fixation test (CFT) were used in parallel to detect anti‐Brucella spp. antibodies. Commercial ELISAs were used to test for antibodies against the other selected pathogens. Sera positive for BTV and Pestivirus by ELISA were tested by serum neutralization test (SNT) to identify circulating serotypes/genotypes. The overall seroprevalences were as follows: 0.4% for Brucella spp. (2/549; CI 95%: 0.1–1.3) (14/555 positive by RBT; 2/564 by CFT), 0.5% for MAP (3/564; CI 95%: 0.1–1.5), 5.7% for M. agalactiae (30/529; CI 95%: 3.9–8.0), 11.1% for Pestivirus (58/525; CI 95%: 8.5–14.1) and 3.3% for BTV (18/538; CI 95%: 2.0–5.2). Significantly higher seropositivity to both M. agalactiae and BTV was observed in P1 compared with P2. Spatiotemporal clusters of high seroprevalence were also found for M. agalactiae in four of the five sampling areas in 2010, and for BTV in one of five areas in 2012. Specific antibodies against BTV‐4, BDV‐4 and BVDV‐1 were confirmed by SNT. Our results indicate that the Iberian ibex may be considered spillover hosts of Brucella spp. and MAP rather than true reservoirs. The prevalence of antibodies against M. agalactiae and BTV suggests spatiotemporal variation in the circulation of these pathogens, while Pestivirus has a moderately endemic circulation in Iberian ibex populations. Our study highlights the importance of long‐term surveillance for a better understanding of the spatiotemporal distribution of shared infectious diseases and providing valuable information to improve control measures at the wildlife–livestock interface.info:eu-repo/semantics/acceptedVersio