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Herein, we report the catalytic activity of a series of platinum(II) pre‐catalysts, bearing N‐heterocyclic carbene (NHC) ligands, in the alkene hydrosilylation reaction. Their structural and electronic properties are fully investigated using X‐ray diffraction analysis and nuclear magnetic resonance spectroscopy (NMR). Next, our study presents a structure‐activity relationship within this group of pre‐catalysts and gives mechanistic insights into the catalyst activation step. An exceptional catalytic performance of one of the complexes is observed, reaching a turnover number (TON) of 970 000 and a turnover frequency (TOF) of 40 417 h−1 at 1 ppm catalyst loading. Finally, an attractive solvent‐free and open‐to‐air alkene hydrosilylation protocol, featuring efficient platinum removal (reduction of residual Pt from 582 ppm to 5.8 ppm), is disclosed. [ABSTRACT FROM AUTHOR]

The reactivity of aryl monocarboxylic acids (benzoic, 1‐ or 2‐naphtoic, 4'‐methylbiphenyl‐4‐carboxylic, and anthracene‐9‐carboxylic acids) as complexing agents for the ethoxide niobium(V) (Nb(OEt)5 precursor has been investigated. A total of eight coordination complexes were isolated with distinct niobium(V) nuclearities as well as carboxylate complexation states. The use of benzoic acid gives a tetranuclear core Nb4(μ2‐O)4(L)4(OEt)8] (L=benzoate (1)) with four Nb−(μ2‐O)−Nb linkages in a square plane configuration. A similar tetramer, 7, was obtained with 2‐naphtoic acid by using a 55 % humid atmosphere synthetic route. Two types of dinuclear brick were identified with one central Nb−(μ2‐O)−Nb linkage; they differ in their complexation state, with one bridging carboxylate ([Nb2(μ2‐O)(μ2‐OEt)(L)(OEt)6], with L=1‐naphtoate (3) or anthracene‐9‐carboxylate (5)) or two bridging carboxylate groups ([Nb2(μ2‐O)(L)2(OEt)6], with L=4'‐methylbiphenyl‐4‐carboxylic (4) or anthracene‐9‐carboxylate (6)). An octanuclear moiety [Nb8(μ2‐O)12(L)8(η1‐L)4−x(OEt)4+x] (with L=2‐naphtoate, x=0 or 2; 8) was obtained by using a solvothermal route in acetonitrile; it has a cubic configuration with niobium centers at each node, linked by 12 μ2‐O groups. The formation of the niobium oxo clusters was characterized by infrared and liquid 1H NMR spectroscopy in order to analyze the esterification reaction, which induces the release of water molecules that further react through oxolation with niobium atoms, in different {Nb2O}, {Nb4O4} and {Nb8O12} nuclearities. [ABSTRACT FROM AUTHOR]

(E)‐Azobenzene is introduced as a suitable chemical actinometer in the visible spectral range (440–540 nm) for photon flux determination of fluidic microphotoreactors or for assessing efficiency of visible light photo‐induced reactions, its evaluation is straightforward without tedious analytics. Photoisomerization quantum yields (ΦE→Z) of (E)‐azobenzene were accurately determined upon irradiation at several wavelengths and in different solvents based on well‐known diarylethene. [ABSTRACT FROM AUTHOR]

A single and accessible cationic iridiumIII metallacycle effectively catalyzes the one‐pot sequential double hydrosilylation of challenging α,β‐unsaturated secondary and tertiary amides to afford, in a controlled and straightforward way, the corresponding reduced products, namely, the related secondary and tertiary amides and amines. The catalytic hydrosilylations of the conjugated amides described herein proceeded in good yields and high chemoselectivities. The critical silyl enolate, in other words silyl ketene aminal intermediate, has been observed and characterized by using control experiments, mass spectrometry and state of the art NMR analyses. The present achievements indicate a promising potential of catalysts based on metallacycles for future significant developments in one‐pot multicatalytic synthesis and therefore the production of highly functionalized and complex organic molecules. [ABSTRACT FROM AUTHOR]

Enantiopure poly(lactic acid) (PLA) can form stereocomplexes when enantiomeric PLA chains are mixed in equivalent amounts. Such materials provide interesting features that might be suitable for numerous applications. Despite several advantages, the main drawback of PLA is its narrow window of processing, thus limiting its use for industrial applications. Reported herein are achiral iron complexes, that are highly active, productive, and stereoselective under mild reaction conditions for the ring‐opening polymerization of lactide. The corresponding catalytic systems enable the production of stereoblock polymers with high molecular weights, allowing the formation of thermally stable and industrially relevant stereocomplexes. [ABSTRACT FROM AUTHOR]

In the present study, we report the first silver-dependent enantiodivergent gold-catalysed reaction. The asymmetric intramolecular hydroamination of alkenes catalysed by the combination of a single chiral binuclear gold(I) chloride complex and silver perchlorate can afford both enantiomers of the products by a simple solvent change from toluene to methanol. Such an enantiodivergent reaction is strictly independent of the reaction temperature or of the nature of the catalyst anion and displays the same first-order kinetic rate law with respect to substrate concentration in both solvents. Beyond a simple solvent effect the enantioinversion is controlled by gold-silver chloride adducts which occur only in methanol and allow a dual activation of the reagent. While one single gold atom activates the alkene moiety, the other gold atom forms an oxophilic gold-silver chloride adduct which is likely to interact with the carbamate function. By comparison with toluene, which affords ( S)-enantiomer, this proximal and bimetallic activation would allow an opposite stereodifferentiation of the two diastereomeric intermediates during the final protodeauration step and lead therefore to the ( R)-enantiomer. [ABSTRACT FROM AUTHOR]

The catalytic acceptorless dehydrogenative oxidation of biosourced alcohols into carboxylic acid salts was achieved using earth-abundant Fe and Mn complexes that feature aliphatic PNP pincer ligands in good to excellent yields. The Fe derivatives were characterized by using 57Fe NMR spectroscopy. Mn pincer catalysts are catalytically more efficient than their Fe counterparts thanks to their robustness under basic conditions. Attempts to generate aldehydes from alcohols were not successful using the Fe and Mn species, but a commercially available Ru analogue achieves this transformation selectively under very mild conditions in the presence of a large excess of acetone as a hydrogen acceptor. [ABSTRACT FROM AUTHOR]

Readily accessible cationic IrIII metallacycles catalyze efficiently the chemoselective hydrosilylation of tertiary and secondary amides to amines. The catalyst described herein operates at low loadings using inexpensive 1,1,3,3-tetramethyldisiloxane and allows fast reactions with high yields, selectivities, and turnover numbers. A transient iminium intermediate has been observed for the first time by using mass spectrometry, and the activation of the catalyst and the silane reagent have been studied by using DFT calculations. These fundamental insights support the present and future improvements of IrIII metallacycles through proper ligand modifications and enable further broad applications of catalysts based on metallacycles. [ABSTRACT FROM AUTHOR]

The reaction of Na10[α-SiW9O34] with 4f tetravalent cerium cations in aqueous solution in the presence of sodium acetate at different pH values leads to the stabilization of three cerium-based polyanionic molecular clusters [Ce3(µ2-OH)3(µ3-O)(SiW9O34)2]13- ( 1), [Ce3(µ2-O)3(SiW9O34)2]14- ( 2), and {[Ce6(µ3-O)4(µ3-OH)4]2(W8O32)(SiW9O34)4}32- ( 3). The condensation behavior of cerium in this kind of association with trivacant polyoxometalates (POMs) when a pH variation occurs is relatively unknown and needed to be explored. Compounds 1 and 2 consist of a trinuclear cerium cluster fragment stabilized by two POM moieties with a variation of the central cerium cluster from [Ce3(µ2-OH)3(µ3-O)] to [Ce3(µ2-O)3]. Compound 3 appears much more condensed with two hexanuclear [Ce6(µ3-O)4(µ3-OH)4] groups that are stabilized by the SiW9O34 moieties and a W8O32 tungsten ring. This evolution in cluster size and composition reflects the pH variation applied during their synthesis. The molecules have been characterized by single-crystal X-ray diffraction, 183W and 29Si NMR spectroscopy, IR spectroscopy, thermogravimetric analysis (TGA), and SEM/energy-dispersive X-ray (EDX) microscopy. The three compounds obtained here exemplify the influence of pH on the condensation of tetravalent cations and open a new route toward the stabilization of polynuclear tetravalent clusters by nucleophilic O-donating POM species. [ABSTRACT FROM AUTHOR]

The catalytic conversion of alcohols into carboxylic acid salts in water was performed in the presence of ruthenium complexes supported by aliphatic PNP pincer ligands preformed or formed in situ. High activity toward a wide substrate scope was achieved with turnover number values of up to 4000. The air-stable catalytic system can be recycled by using toluene as a catalyst-immobilizing phase; the activity is maintained after five consecutive runs. Finally, mechanistic studies allowed some fundamental aspects related to water activation to be unveiled and to the mechanism postulated. [ABSTRACT FROM AUTHOR]

In the background is featured Ginkakuji (Silver Pavilion), a Zen temple along Kyoto′s eastern mountains (Higashiyama) in Japan. In the foreground is featured a chemistry sketch based on the Yin and Yang symbol. As many possible dualities (such as light and dark, fire and water…) are thought of as physical manifestations of the duality symbolised by Yin and Yang, parallels can be drawn with organic chemistry and the gold(I)‐catalysed asymmetric hydroamination of alkenes. An enantiodivergent reaction is possible depending on the presence of silver. Whereas a gold‐catalysed hydroamination reaction afforded (S)‐product in toluene, the use of methanol led to an enantioinversion and the generation of (R)‐product through solvation of silver and bimetallic activation of the amino‐alkene reagent. For more information see the Full Paper by F. Agbossou‐Niedercorn, C. Michon and co‐workers on page 10777 ff. [ABSTRACT FROM AUTHOR]

The Cover picture shows how ruthenium pincer complexes catalyze the oxidation of alcohols into carboxylic acids in water, which acts as the oxygen source while H2 is released as the only by‐product, as illustrated by the bubbles. More details can be found in the Full Paper by Zhang et al. on page 1413 in Issue 12, 2016 (DOI: 10.1002/cssc.201600243). [ABSTRACT FROM AUTHOR]