Search

Amid global concern regarding the health and environmental impacts of per‐ and polyfluoroalkyl substances (PFAS), there is an urgent need to develop and implement alternative products without PFAS. Consequently, PFAS‐free firefighting foams used for fire suppression have been developed for use in military and residential settings. To facilitate the selection of lower‐risk PFAS‐free foams, the present study focused on the chronic toxicity of seven PFAS‐free and one PFAS‐containing foam to six aquatic species. Target species included two cladocerans, Daphnia magna and Ceriodaphnia dubia; the chironomid Chironomus dilutus; the mysid Americamysis bahia; and two fish species, Pimephales promelas and Cyprinodon variegatus, with endpoints including growth, development, reproduction, and survival. To facilitate comparison and product toxicity rankings, effective concentrations (20%, 50%) and no‐ and lowest‐observed‐effect concentrations (NOECs and LOECs, respectively) were calculated. Effective concentrations, NOECs, and LOECs varied by over an order of magnitude among foams and species, with several of the PFAS‐free formulations ranked as highly toxic based on US Environmental Protection Agency alternatives assessment hazard criteria. Overall, the PFAS‐free foams were found to exhibit either similar or greater toxicity compared to the PFAS‐containing reference foam across several species and endpoints. Nonmonotonic and hormetic dose responses were observed in D. magna for several of the tested foams, with increased reproduction and growth at intermediate exposures. Generally, tested foam toxicity rankings were consistent with a related acute toxicity study using the same species and formulations, and other research using soil invertebrates. Combined with related efforts for other taxa including mammals, birds, and plants, the present research will facilitate the selection of appropriate PFAS‐free firefighting foams that minimize harm to the environment. Environ Toxicol Chem 2024;43:2436–2454. © 2024 SETAC [ABSTRACT FROM AUTHOR]

The solid‐state structures of the first rubidium and caesium pentalenides [Rb(THF)]2[Ph4Pn] and [Cs(THF)]2[Ph4Pn] have been determined by single crystal X‐ray diffraction. Both were found to be polymeric in the solid state through interactions of the cations with the phenyl substituents, in contrast to their lighter group 1 congeners which are monomeric for lithium and sodium, and THF‐bridged for potassium. Both [Rb(THF)]2[Ph4Pn] and [Cs(THF)]2[Ph4Pn] displayed increased η8 coordination, demonstrating a shift towards higher hapticities down the group as previously predicted computationally for the parent M2[Pn] complexes (M=group 1 metal). The solid‐state structures of the polydentate donor adducts [M(DME)x]2[Ph4Pn] (M=Li, x=1; M=Na, x=2) and [M(Me6TREN)]2[Ph4Pn] (M=K, Rb, Cs) were all monomeric and displayed increased metal‐carbon distances and decreased ring slippage values relative to the THF adducts. [ABSTRACT FROM AUTHOR]

Treating the amide acetanilide (N‐phenylacetamide, C8H9NO) with aqueous strong acids allowed the structures of five hemi‐protonated salt forms of acetanilide to be elucidated. N‐(1‐Hydroxyethylidene)anilinium chloride–N‐phenylacetamide (1/1), [(C8H9NO)2H][Cl], and the bromide, [(C8H9NO)2H][Br], triiodide, [(C8H9NO)2H][I3], tetrafluoroborate, [(C8H9NO)2H][BF4], and diiodobromide hemi(diiodine), [(C8H9NO)2H][I2Br]·0.5I2, analogues all feature centrosymmetric dimeric units linked by O—H...O hydrogen bonds that extend into one‐dimensional hydrogen‐bonded chains through N—H...X interactions, where X is the halide atom of the anion. Protonation occurs at the amide O atom and results in systematic lengthening of the C=O bond and a corresponding shortening of the C—N bond. The size of these geometric changes is similar to those found for hemi‐protonated paracetamol structures, but less than those in fully protonated paracetamol structures. The bond angles of the amide fragments are also found to change on protonation, but these angular changes are also influenced by conformation, namely, whether the amide group is coplanar with the phenyl ring or twisted out of plane. [ABSTRACT FROM AUTHOR]

While organoelement compounds of lithium, sodium and potassium have been much studied for decades and consequently have found forests of applications, those of the heavier alkali metals, rubidium and caesium would barely manage to fill a tree. However, recently the literature has seen some little growth spurts with these metals, hinting at a possible fertile future in areas such as homogeneous catalysis provided more work is put into their fundamental development. Here we report the synthesis and crystal structures of lithium, rubidium and caesium derivatives of the ureaphosphane Ph2PCH2CH2NHC(=O)NHPh, chosen because it offers O, N, P, and π‐coordination sites. Though one may expect such alkali metal compounds to be essentially similar, the caesium complex has novel features where Cs+ engages in a side‐on coordination to the C=O bond and in a weak bond to the P centre, both of which are absent in the Rb structure. Less surprisingly, the lithium derivative is tetrameric in contrast to the infinite networks of the rubidium and caesium structures. All alkali metal derivatives were made with deprotonating the ureaphosphane by a suitable base, including the sodium and potassium complexes though these two complexes could not be obtained in a crystalline form. [ABSTRACT FROM AUTHOR]

A widely utilised class of ligands in synthesis and catalysis, β‐diketiminate (BDI) or NacNac compounds were initially considered innocent in the sense that they remained intact in all their applications. That changed when the γ‐C−H unit of their NCCCN backbone was found to engage in reactions with electrophiles. Here, we show that this special reactivity can be used advantageously to prepare tripodal modifications of the common NacNac ligand derived from 2,6‐diisopropylphenyl‐β‐methyldiketimine [NacNacH (Me, Dipp)]. Lithiation to give NacNacLi, followed by reactions with isocyanates, isothiocyanates and a carbodiimide, have afforded a series of tripodal NacNac variants having N,N,N,O; N,N,N,S; or N,N,N,N potential dentation sites, many of which have been crystallographically characterised. Distinct ligating modes of these new ligands have been elucidated through the crystal structures of their lithiated derivatives. [ABSTRACT FROM AUTHOR]

The structures of five ammonium salt forms of monosulfonated azo dyes, derivatives of 4‐(2‐phenyldiazen‐1‐yl)benzenesulfonate, with the general formula [NH4][O3S(C6H4)NN(C6H3)RR′]·XH2O [R = OH, NH2 or N(C2H4OH)2; R′ = H or OH] are presented. All form simple layered structures with alternating hydrophobic (organic) and hydrophilic (cation, solvent and polar groups) layers. To assess for isostructural behaviour of the ammonium cation with M+ ions, the packing of these structures is compared with literature examples. To aid this comparison, the corresponding structures of four potassium salt forms of the monosulfonated azo dyes are also presented herein. Of the five ammonium salts it is found that three have isostructural equivalents. In two cases this equivalent is a potassium salt form and in one case it is a rubidium salt form. The isostructurality of ion packing and of unit‐cell symmetry and dimensions tolerates cases where the ammonium ions form somewhat different interaction types with coformer species than do the potassium or rubidium ions. No sodium salt forms are found to be isostructural with any ammonium equivalent. However, similarities in the anion packing within a single hydrophobic layer are found for a group that consists of the ammonium and rubidium salt forms of one azo anion species and the sodium and silver salt forms of a different azo species. [ABSTRACT FROM AUTHOR]

Tethered N‐heterocyclic carbenes (NHCs) are an emerging class of ligand, as they feature all the desirable aspects of NHCs (ease of synthesis, high tunabilty) but also enable metal‐ligand cooperativity when combined with Lewis acidic metal centres due to the donor‐acceptor nature of the complexes formed. Herein we report a simple ethoxy‐tethered NHC for the stabilisation of Al(III) hydrides, resulting in the unexpected formation of a bicyclic N‐heterocyclic aminal (1). Compound 1 behaves as a metal hydride, capable of reducing benzophenone and carbodiimide to yield compounds 2 and 3, respectively. Furthermore, we show that 1 behaves as an efficient catalyst in the dehydrocoupling of amine‐boranes due to the hemi‐labile nature of the supporting ligand. [ABSTRACT FROM AUTHOR]

Freshwater aquaculture can have negative impacts on chemical, physical and biological water quality. To contextualise the impact that these activities may have, a case study site in Ireland was monitored for 1 year. The study aims were to investigate the impact of freshwater aquaculture on water quality (biological, physical, and chemical) and the degree of the impact and recovery in water quality, within 1000 m downstream of a salmon smolt hatchery. The hatchery was monitored, at four locations (upstream, 10, 100, and 1,000 m downstream of the discharge point). Data on macroinvertebrate, macrophyte, hydromorphology and chemical characteristics were collected. Results for the physical monitoring indicated no significant changes in hydromorphology between up and downstream sites. Chemical water quality did decrease downstream in terms of nitrogen (N) and phosphorus (P). The greatest concentrations in N and P were found at 1000 m though it is likely additional contributions from agriculture impacted this site. Dissolved oxygen was steady throughout the monitoring campaign with a 13% variance between upstream and downstream locations. Changes in biological indices were statistically significant for taxa at all downstream sites. There were positive trends which indicated a degree of recovery in biotic indices. [ABSTRACT FROM AUTHOR]

A prior multigenerational perfluorooctane sulfonic acid (PFOS) exposure investigation in zebrafish reported adverse effects at 0.734 µg/L, among the lowest aquatic effect levels for PFOS reported to date. The present three‐generation PFOS exposure quantified survival, growth, reproduction, and vitellogenin (VTG; egg yolk protein) responses in zebrafish, incorporating experimental design and procedural improvements relative to the earlier study. Exposures targeting 0.1, 0.6, 3.2, 20, and 100 µg/L in parental (P) and first filial (F1) generations lasted for 180 days post fertilization (dpf) and the second filial generation (F2) through 16 dpf. Survival decreased significantly in P and F2 generation exposures, but not in F1, at the highest PFOS treatment (100 µg/L nominal, 94–205 µg/L, measured). Significant adverse effects on body weight and length were infrequent, of low magnitude, and occurred predominantly at the highest exposure treatment. Finally, PFOS had no significant effects on P or F1 egg production and survival or whole‐body VTG levels in P or F1 male fish. Overall, the predominance and magnitude of adverse PFOS effects at <1 µg/L reported in prior research were largely nonrepeatable in the present study. In contrast, the present study indicated a threshold for ecologically relevant adverse effects in zebrafish at 117 µg/L (SE 8 µg/L, n = 10) for survival and 47 µg/L (SE 11 µg/L, n = 19) for all statistically significant negative effects observed. Environ Toxicol Chem 2024;43:115–131. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Three distinct routes are reported to the soluble, dihydridoaluminate compounds, AM[Al(NONDipp)(H)2] (AM=Li, Na, K, Rb, Cs; [NONDipp]2−=[O(SiMe2NDipp)2]2−; Dipp=2,6‐iPr2C6H3) starting from the alkali metal aluminyls, AM[Al(NONDipp)]. Direct H2 hydrogenation of the heavier analogues (AM=Rb, Cs) produced the first examples of structurally characterized rubidium and caesium dihydridoaluminates, although harsh conditions were required for complete conversion. Using 1,4‐cyclohexadiene (1,4‐CHD) as an alternative hydrogen source in transfer hydrogenation reactions provided a lower energy pathway to the full series of products for AM=Li−Cs. A further moderation in conditions was noted for the thermal decomposition of the (silyl)(hydrido)aluminates, AM[Al(NONDipp)(H)(SiH2Ph)]. Probing the reaction of Cs[Al(NONDipp)] with 1,4‐CHD provided access to a novel inverse sandwich complex, [{Cs(Et2O)}2{Al(NONDipp)(H)}2(C6H6)], containing the 1,4‐dialuminated [C6H6]2− dianion and representing the first time that an intermediate in the commonly utilized oxidation process of 1,4‐CHD to benzene has been trapped. The synthetic utility of the newly installed Al−H bonds has been demonstrated by their ability to reduce CO2 under mild conditions to form the bis‐formate AM[Al(NONDipp)(O2CH)2] compounds, which exhibit a diverse series of eyecatching bimetallacyclic structures. [ABSTRACT FROM AUTHOR]

The structures of four salt forms of dopamine are reported. These are dopamine [2‐(3,4‐dihydroxyphenyl)ethan‐1‐aminium] benzoate, C8H12NO2+·C7H5O2−, I, dopamine 4‐nitrobenzoate, C8H12NO2+·C7H4NO4−, II, dopamine ethanedisulfonate, 2C8H12NO2+·C2H4O6S22−, III, and dopamine 4‐hydroxybenzenesulfonate monohydrate, C8H12NO2+·C6H5O4S−·H2O, IV. In all four structures, the dopamine cation adopts an extended conformation. Intermolecular interaction motifs that are common in the salt forms of tyramine can be found in related dopamine structures, but hydrogen bonding in the dopamine structures appear to be more variable and less predictable than for tyramine. Packing analysis discovered three dopamine‐containing groups of structures that can be described as isostructural with regards to the cation positions. Two of these groups contain both dopamine and tyramine species, and one of these is also highly variable in other ways too, containing anhydrous and hydrated forms, different anion types and ionized and neutral phenylethylamine species. As such, the group illustrates that packing behaviour can be robust and similar even where intermolecular interactions such as hydrogen bonds are very different. [ABSTRACT FROM AUTHOR]

Chiral molecules are known to behave as spin filters due to the chiral induced spin selectivity (CISS) effect. Chirality can be implemented in molecular semiconductors in order to study the role of the CISS effect in charge transport and to find new materials for spintronic applications. In this study, the design and synthesis of a new class of enantiopure chiral organic semiconductors based on the well‐known dinaphtho[2,3‐b:2,3‐f]thieno[3,2‐b]thiophene (DNTT) core functionalized with chiral alkyl side chains is presented. When introduced in an organic field‐effect transistor (OFET) with magnetic contacts, the two enantiomers, (R)‐DNTT and (S)‐DNTT, show an opposite behavior with respect to the relative direction of the magnetization of the contacts, oriented by an external magnetic field. Each enantiomer displays an unexpectedly high magnetoresistance over one preferred orientation of the spin current injected from the magnetic contacts. The result is the first reported OFET in which the current can be switched on and off upon inversion of the direction of the applied external magnetic field. This work contributes to the general understanding of the CISS effect and opens new avenues for the introduction of organic materials in spintronic devices. [ABSTRACT FROM AUTHOR]

Catalytic reduction of a representative set of imines, both aldimines and ketimines, to amines has been studied using transfer hydrogenation from 1,4‐dicyclohexadiene. Unusually, this has been achieved using s‐block pre‐catalysts, namely 1‐metallo‐2‐tert‐butyl‐1,2‐dihydropyridines, 2‐tBuC5H5NM, M(tBuDHP), where M=Li–Cs. Reactions have been monitored in C6D6 and tetrahydrofuran‐d8 (THF‐d8). A definite trend is observed in catalyst efficiency with the heavier alkali metal tBuDHPs outperforming the lighter congeners. In general, Cs(tBuDHP) is the optimal pre‐catalyst with, in the best cases, reactions producing quantitative yields of amines in minutes at room temperature using 5 mol % catalyst. Supporting the experimental study, Density Functional Theory (DFT) calculations have also been carried out which reveal that Cs has a pathway with a significantly lower rate determining step than the Li congener. In the postulated initiation pathways DHP can act as either a base or as a surrogate hydride. [ABSTRACT FROM AUTHOR]

Exploiting bimetallic cooperation alkali‐metal manganate (II) complexes can efficiently promote oxidative homocoupling of terminal alkynes furnishing an array of conjugated 1,3‐diynes. The influence of the alkali‐metal on these C−C bond forming processes has been studied by preparing and structurally characterizing the alkali‐metal tetra(alkyl) manganates [(TMEDA)2Na2Mn(CH2SiMe3)4] and [(PMDETA)2K2Mn(CH2SiMe3)4]. Reactivity studies using phenylacetylene as a model substrate have revealed that for the homocoupling to take place initial metalation of the alkyne is required. In this regard, the lack of basicity of neutral Mn(CH2SiMe3)2 precludes the formation of the diyne. Contrastingly, the tetra(alkyl) alkali‐metal manganates behave as polybasic reagents, being able to easily deprotonate phenylacetylene yielding [{(THF)4Na2Mn(C≡CPh)4}∞] and [(THF)4Li2Mn(C≡CPh)4]. Controlled exposure of [{(THF)4Na2Mn(C≡CPh)4}∞] and [(THF)4Li2Mn(C≡CPh)4] to dry air confirmed their intermediary in formation of 1,4‐diphenyl‐1,3‐butadiyne in excellent yields. While the Na/Mn(II) partnership proved to be the most efficient in stoichiometric transformations, under catalytic regimes, the combination of MC≡CAr (M= Li, Na) and MnCl2 (6 mol %) only works for lithium, most likely due to the degradation of alkynylsodiums under the aerobic reaction conditions. [ABSTRACT FROM AUTHOR]

Three new ligands containing a bicyclo[2.2.2]oct‐7‐ene‐2,3,5,6‐tetracarboxydiimide unit have been used to assemble lantern‐type metal‐organic cages with the general formula [Cu4L4]. Functionalisation of the backbone of the ligands leads to distinct crystal packing motifs between the three cages, as observed with single‐crystal X‐ray diffraction. The three cages vary in their gas sorption behaviour, and the capacity of the materials for CO2 is found to depend on the activation conditions: softer activation conditions lead to superior uptake, and one of the cages displays the highest BET surface area found for lantern‐type cages so far. [ABSTRACT FROM AUTHOR]

CTLA‐4 and PD‐1 are key immune checkpoint receptors that are targeted in the treatment of cancer. A recently identified physical interaction between the respective ligands, CD80 and PD‐L1, has been shown to block PD‐L1/PD‐1 binding and to prevent PD‐L1 inhibitory functions. Since CTLA‐4 is known to capture and degrade its ligands via transendocytosis, we investigated the interplay between CD80 transendocytosis and CD80/PD‐L1 interaction. We find that transendocytosis of CD80 results in a time‐dependent recovery of PD‐L1 availability that correlates with CD80 removal. Moreover, CD80 transendocytosis is highly specific in that only CD80 is internalised, while its heterodimeric PD‐L1 partner remains on the plasma membrane of the antigen‐presenting cell (APC). CTLA‐4 interactions with CD80 do not appear to be inhibited by PD‐L1, but efficient removal of CD80 requires an intact CTLA‐4 cytoplasmic domain, distinguishing this process from more general trogocytosis and simple CTLA‐4 binding to CD80/PD‐L1 complexes. These data are consistent with CTLA‐4 acting as modulator of PD‐L1:PD‐1 interactions via control of CD80. Synopsis: The CTLA‐4 and PD‐1 immune checkpoint pathways intersect by cis interaction between their respective ligands (CD80 and PD‐L1), which interferes with PD‐L1 binding to PD‐1. Here, CTLA‐4‐mediated transendocytosis is shown to selectively deplete CD80 from the cell surface, resulting in the liberation of functional PD‐L1 that can interact with PD‐1. CD80 interacts with PD‐L1 to form cis heterodimers that prevent binding to PD‐1.CTLA‐4 transendocytosis removes CD80, but not PD‐L1, restoring the ability of PDL1 to bind PD‐1.Binding of CTLA‐4 in soluble or non‐endocytic forms to CD80‐PD‐L1 heterodimers does not effectively release free functional PD‐L1.CTLA‐4 can influence PD‐L1‐PD‐1 interaction and function by controlling CD80 expression. CTLA‐4 regulates PD‐L1‐PD‐1 interactions via transendocytosis of CD80. [ABSTRACT FROM AUTHOR]

Co‐complexation of equimolar amounts of 1‐alkali‐metal‐2‐tertbutyldihydropyridines with AlMe3 in the presence of a polydentate N‐donor ligand has delivered four crystallographically verified alkali‐metal aluminates [donor⋅AM(μ‐tBuDHP)AlMe3]n (1, AM=Li, donor=TMEDA, n=1; 2, AM=Na, donor=PMDETA, n=1; 3, AM=K, donor=PMDETA, n=2; 4, AM=Cs, donor=PMDETA, n=∞; TMEDA=N,N,N′,N′‐tetramethylethylenediamine; PMDETA=N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine). While the monomeric complexes (1, 2) and the polymeric complex (4) are thermally stable, the dimeric complex (3) undergoes a disproportionation process yielding the known ion‐separated homoanionic complex [K ⋅ (PMDETA)2]+ [AlMe4]− (3 a). Utilizing TMEDA as the N‐donor resulted in the same disproportionation, but gave rise to two distinct solid‐state aggregated forms of aluminate [K ⋅ (TMEDA)2]+ [AlMe4]−, namely monomeric (3 b) and polymeric (3 b′) polymorphs, in which the anionic moiety acts as a bidentate chelator or monodentate bridge respectively to the potassium cationic moieties. [ABSTRACT FROM AUTHOR]

A series of group 1 hydrocarbon‐soluble donor free aluminates [AM(tBuDHP)(TMP)Al(iBu)2] (AM=Li, Na, K, Rb) have been synthesised by combining an alkali metal dihydropyridyl unit [(2‐tBuC5H5N)AM)] containing a surrogate hydride (sp3 C−H) with [(iBu)2Al(TMP)]. These aluminates have been characterised by X‐ray crystallography and NMR spectroscopy. While the lithium aluminate forms a monomer, the heavier alkali metal aluminates exist as polymeric chains propagated by non‐covalent interactions between the alkali metal cations and the alkyldihydropyridyl units. Solvates [(THF)Li(tBuDHP)(TMP)Al(iBu)2] and [(TMEDA)Na(tBuDHP)(TMP)Al(iBu)2] have also been crystallographically characterised. Theoretical calculations show how the dispersion forces tend to increase on moving from Li to Rb, as opposed to the electrostatic forces of stabilization, which are orders of magnitude more significant. Having unique structural features, these bimetallic compounds can be considered as starting points for exploring unique reactivity trends as alkali‐metal‐aluminium hydride surrog[ATES]. [ABSTRACT FROM AUTHOR]

Rare examples of heavier alkali metal manganates [{(AM)Mn(CH2SiMe3)(N'Ar)2}∞] (AM=K, Rb, or Cs) [N'Ar=N(SiMe3)(Dipp), where Dipp=2,6‐iPr2‐C6H3] have been synthesised with the Rb and Cs examples crystallographically characterised. These heaviest manganates crystallise as polymeric zig‐zag chains propagated by AM⋅⋅⋅π‐arene interactions. Key to their preparation is to avoid Lewis base donor solvents. In contrast, using multidentate nitrogen donors encourages ligand scrambling leading to redistribution of these bimetallic manganate compounds into their corresponding homometallic species as witnessed for the complete Li ‐ Cs series. Adding to the few known crystallographically characterised unsolvated and solvated rubidium and caesium s‐block metal amides, six new derivatives ([{AM(N'Ar)}∞], [{AM(N'Ar)⋅TMEDA}∞], and [{AM(N'Ar)⋅PMDETA}∞] where AM=Rb or Cs) have been structurally authenticated. Utilising monodentate diethyl ether as a donor, it was also possible to isolate and crystallographically characterise sodium manganate [(Et2O)2Na(nBu)Mn[(N'Ar)2], a monomeric, dinuclear structure prevented from aggregating by two blocking ether ligands bound to sodium. [ABSTRACT FROM AUTHOR]

Introduction of adamantane moieties on diamondoids such as adamantane, 2‐azaadamantane or diamantane by amide formation and reduction to the corresponding amine was performed in a straightforward and easy way by amidation under Schotten–Baumann conditions and reduction with BH3 ⋅ THF. The obtained amides and amines were studied in terms of structural properties towards the perspective of transformation into nanodiamonds. Crystal structure and dynamic NMR experiments of the most crowded amide obtained gave structural insights into the effect of bulkiness and steric strain on out‐of‐planarity of amide bonds (16.0°) and the kinetics and thermodynamics of amide bond rotation (ΔG≠298K=11.5–13.3 kcal ⋅ mol−1). [ABSTRACT FROM AUTHOR]

It is critical to thoroughly investigate, characterize, and understand the unique emission profiles of common and novel polymer feedstocks used in fused filament fabrication (FFF) 3D printers as these products become increasingly ubiquitous in consumer and industrial environments. This work contributes unique insights regarding the effects of polymer composite feedstocks with metal, ceramic, or carbonaceous particle additives on particulate emissions in a variety of filaments under various print conditions, including print temperature. In addition to active characterization of particulate size and concentration following the ANSI/CAN/UL 2904 method, particulate sampling and subsequent analysis by scanning electron microscopy revealed agglomeration behavior that may have important health implications. Specifically, fine particles (0.3–2.5 μm) generated by certain filaments including acrylonitrile butadiene styrene (ABS) and glycol‐modified poly(ethylene terephthalate) (PETG) are shown to be formed via agglomeration of emitted ultrafine particles rather than composed of coherent primary particles; accordingly, transport and behavior of these particulates after inhalation may not follow expected patterns for micrometer‐sized particles. Structures resembling carbonaceous additives (e.g., graphene and nanotubes) were also captured by airborne sampling during printing of filaments containing carbonaceous advanced materials. [ABSTRACT FROM AUTHOR]

We report reactions of LiNacNac and NacNacMg(TMP) with common organic substrates (TMP=2,2,6,6‐tetramethylpiperidide). Using bulky β‐diketiminate compound NacNac (Me, Dipp), we have trapped metalated intermediates amenable to X‐ray crystallographic study. LiNacNac and acetone produced the NacNac‐free hexameric diacetone alkoxide [{LiO(MeC(=O)CH2C(Me)2}6]; whereas pinacolone gave the simple monomeric donor–acceptor complex [Li{(MeCN‐2,6‐iPr2C6H3)2CH}{O=C(Me)tBu}]. Benzaldehyde produced dimeric [Li{(MeCN‐2,6‐iPr2C6H3)2CC(=O)Ph}{O=C(Ph)OCH2Ph}]2, where one benzaldehyde molecule has inserted in to the γ‐carbon position of the NacNac ligand, with a molecule of benzyl benzoate derived from a Tishchenko reaction of the aldehyde acting as a terminal donor to lithium. Tetranuclear, mixed dimer [{LiO(MeCN‐2,6‐iPr2C6H3)2CH‐CH(Ph)}2{LiO(PhC(=O)}2] containing the same modified NacNac ligand was the fortuitous product from repeating the reaction of LiNacNac and benzaldehyde in a solution presumably contaminated with benzoic acid. Combining NacNacMg(TMP) with pinacolone affords monomeric heteroleptic [Mg{(MeCN‐2,6‐iPr2C6H3)2CH}{OC(tBu)(Me)CH2C(=O)tBu}] with an aldolate constituting the second anion. Completing the set is dimeric [Mg{(MeCN‐2,6‐iPr2C6H3)2CH}{O(C=CH2)Ph}2], where the enolate derived from acetophenone bridges the magnesium centres. [ABSTRACT FROM AUTHOR]

We evaluated the precision and accuracy of multilaboratory measurements for determining freely dissolved concentrations (Cfree) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in sediment porewater using polydimethylsiloxane (PDMS) and low‐density polyethylene (LDPE) polymeric samplers. Four laboratories exposed performance reference compound (PRC) preloaded polymers to actively mixed and static ex situ sediment for approximately 1 month; two laboratories had longer exposures (2 and 3 months). For Cfree results, intralaboratory precision was high for single compounds (coefficient of variation 50% or less), and for most PAHs and PCBs interlaboratory variability was low (magnitude of difference was a factor of 2 or less) across polymers and exposure methods. Variability was higher for the most hydrophobic PAHs and PCBs, which were present at low concentrations and required larger PRC‐based corrections, and also for naphthalene, likely due to differential volatilization losses between laboratories. Overall, intra‐ and interlaboratory variability between methods (PDMS vs. LDPE, actively mixed vs. static exposures) was low. The results that showed Cfree polymer equilibrium was achieved in approximately 1 month during active exposures, suggesting that the use of PRCs may be avoided for ex situ analysis using comparable active exposure; however, such ex situ testing may not reflect field conditions. Polymer‐derived Cfree concentrations for most PCBs and PAHs were on average within a factor of 2 compared with concentrations in isolated porewater, which were directly measured by one laboratory; difference factors of up to 6 were observed for naphthalene and the most hydrophobic PAHs and PCBs. The Cfree results were similar for academic and private sector laboratories. The accuracy and precision that we demonstrate for determination of Cfree using polymer sampling are anticipated to increase regulatory acceptance and confidence in use of the method. Environ Toxicol Chem 2022;41:1885–1902. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

The charge transport of crystalline organic semiconductors is limited by dynamic disorder that tends to localize charges. It is the main hurdle to overcome in order to significantly increase charge carrier mobility. An innovative design that combines a chemical structure based on sulfur‐rich thienoacene with a solid‐state herringbone (HB) packing is proposed and the synthesis, physicochemical characterization, and charge transport properties of two new thienoacenes bearing a central tetrathienyl core fused with two external naphthyl rings: naphtho[2,3‐b]thieno‐[2′′′,3′′′:4′′,5′′]thieno[2″,3″:4′,5′]thieno[3′,2′‐b]naphtho[2,3‐b]thiophene (DN4T) and naphtho[1,2‐b]thieno‐[2′′′,3′′′:4′′,5′′]thieno[2′′,3′′:4′,5′]thieno[3′,2′‐b]naphtho[1,2‐b]thiophene are presented. Both compounds crystallize with a HB pattern structure and present transfer integrals ranging from 33 to 99 meV (for the former) within the HB plane of charge transport. Molecular dynamics simulations point toward an efficient resilience of the transfer integrals to the intermolecular sliding motion commonly responsible for strong variations of the electronic coupling in the crystal. Best device performances are reached with DN4T with hole mobility up to μ = 2.1 cm2 V−1s−1 in polycrystalline organic field effect transistors, showing the effectiveness of the electronic coupling enabled by the new aromatic core. These promising results pave the way to the design of high‐performing materials based on this new thienoacene, notably through the introduction of alkyl side‐chains. [ABSTRACT FROM AUTHOR]

Arylmethyl anions allow alkali‐metals to bind in a σ‐fashion to the lateral carbanionic centre or a π‐fashion to the aryl ring or in between these extremities, with the trend towards π bonding increasing on descending group 1. Here we review known alkali metal structures of diphenylmethane, fluorene, 2‐benzylpyridine and 4‐benzylpyridine. Next, we synthesise Li, Na, K monomers of these diarylmethyls using polydentate donors PMDETA or Me6TREN to remove competing oligomerizing interactions, studying the effect that two aromatic rings has on negative charge (de)localisation via NMR, X‐ray crystallographic and DFT studies. Diphenylmethyl and fluorenyl anions maintain C(H)−M interactions regardless of alkali‐metal, although the adjacent arene carbons engage in interactions with larger alkali‐metals. Introducing a nitrogen atom into the ring (at the 2‐ or 4‐position) encourages relocalisation of negative charge away from the deprotonated carbon and onto nitrogen. Phenyl(2‐pyridyl)methyl moves from an enamide formation at one extremity (lithium) to an aza‐allyl formation at the other extremity (potassium), while C‐ or N‐coordination modes become energetically viable for Na and K phenyl(4‐pyridyl)methyl complexes. [ABSTRACT FROM AUTHOR]

The use of a sodium in sodium chloride dispersion is systematically evaluated for the synthesis of nickel(0) and nickel(I) complexes from readily‐prepared nickel(II) precursors. A variety of complexes with phosphine and bipyridine‐type ligands were accessed, although some reactions were found to produce mixtures of nickel(0) and nickel(I), and yields were highly variable. Several new nickel(I) complexes were obtained, and these were characterized using techniques including NMR spectroscopy, EPR spectroscopy, and single crystal X‐ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Exploiting chemical cooperation between Na and Fe(II) within the bimetallic base [dioxane ⋅ NaFe(HMDS)3] (I), (dioxane=1,4‐dioxane, HMDS=N(SiMe3)2) the selective ferration of fluorobenzene, 1‐fluoronaphthalene, 1,4‐difluorobenzene, 1,2,4‐trifluorobenzene, 1,3,5‐trifluorobenzene, 1‐bromo‐3,5‐difluorobenzene, 3‐fluoroanisole and 3,5‐difluoroanisole has been realized, affording sodium ferrates [dioxane ⋅ Na(HMDS)(2‐F‐C6H4)Fe(HMDS)]∞ (1), [dioxane ⋅ Na(HMDS)(2‐F‐C10H6)Fe(HMDS)]∞ (2), [dioxane ⋅ {Na(HMDS)(2,5‐F2‐C6H3)Fe(HMDS)}2]∞ (3), [dioxane ⋅ {Na(HMDS)(2,3,6‐F3‐C6H2)Fe(HMDS)}2]∞ (4), [(dioxane)1.5 ⋅ Na(HMDS)(2,4,6‐F3‐C6H2)Fe(HMDS)]2 (5), [(dioxane)1.5 ⋅ {Na(HMDS)(4‐Br‐2,6‐F2‐C6H2)Fe(HMDS)2] (6), [{(dioxane)2 ⋅ Na2Fe(HMDS)2(2‐methoxy‐6‐F‐C6H3)}+{Fe(HMDS)3}−]∞ (7) and [dioxane ⋅ {Na(HMDS)(4‐methoxy‐2,6‐F2‐C6H2)Fe(HMDS)}2]∞ (8), respectively. Reactions take place under mild reaction conditions, with excellent control of the selectivity and no competing C−F bond activation is observed. Showcasing complex polymeric arrangements in some cases, the structures of compounds 1–8 have been determined by X‐ray crystallographic studies. In all cases, the Fe(II) centers occupy the position in the relevant fluoroarene that was previously filled by a proton, confirming that these metallations are actually ferration processes whereas the Na atoms prefer to form Na⋅⋅⋅F dative interactions. Compounds 1–8 are thermally stable and do not undergo benzyne formation (through NaF elimination) and their formation contrasts with the inertness of Fe(HMDS)2 which fails to act as a base to metallate fluoroarenes. [ABSTRACT FROM AUTHOR]

Alkali‐metal ferrates containing amide groups have emerged as regioselective bases capable of promoting Fe−H exchanges of aromatic substrates. Advancing this area of heterobimetallic chemistry, a new series of sodium ferrates is introduced incorporating the bulky arylsilyl amido ligand N(SiMe3)(Dipp) (Dipp=2,6‐iPr2‐C6H3). Influenced by the large steric demands imposed by this amide, transamination of [NaFe(HMDS)3] (HMDS=N(SiMe3)2) with an excess of HN(SiMe3)(Dipp) led to the isolation of heteroleptic [Na(HMDS)2Fe{N(SiMe3)Dipp}]∞ (1) resulting from the exchange of just one HMDS group. An alternative co‐complexation approach, combining the homometallic metal amides [NaN(SiMe3)Dipp] and [Fe{N(SiMe3)Dipp}2] induces lateral metallation of one Me arm from the SiMe3 group in the iron amide furnishing tetrameric [NaFe{N(SiCH2Me2)Dipp}{N(SiMe3)Dipp}]4 (2). Reactivity studies support that this deprotonation is driven by the steric incompatibility of the single metal amides rather than the basic capability of the sodium reagent. Displaying synergistic reactivity, heteroleptic sodium ferrate 1 can selectively promote ferration of pentafluorobenzene using one of its HMDS arms to give heterotrileptic [Na{N(SiMe3)Dipp}(HMDS)Fe(C6F5)]∞ (4). Attempts to deprotonate less activated pyridine led to the isolation of NaHMDS and heteroleptic Fe(II) amide [(py)Fe{N(SiMe3)Dipp}(HMDS)] (5), resulting from an alternative redistribution process which is favoured by the Lewis donor ability of this substrate. [ABSTRACT FROM AUTHOR]

Literature on Group One organoelement chemistry is dominated by lithium, though sodium and potassium also feature prominently, whereas rubidium and caesium are rarely mentioned. With recent breakthroughs hinting that organoelement compounds of these two heavier metals can perform better than their lighter congeners in particular applications, important advantages could be missed unless complete sets of alkali metals are included in studies. Here, we report the synthesis and characterisation of a complete set of multi‐alkali‐metallated molecular compounds of the 1,3,5‐tris[(4,6‐dimethylpyridin‐2‐yl)aminomethyl]‐2,4,6‐triethylbenzene framework. Made by deprotonating the framework N−H bonds by a suitable base, the set comprises six THF‐solvated compounds, four of which are homometallic, either containing Li in a trinuclear structure or Na, K, and Rb in hexanuclear structures. Since deprotonation was incomplete with Cs, its homometallic compound is tetranuclear containing two un‐metallated N−H bonds. A heterobimetallic trilithium‐tricaesium hexanuclear compound was also obtained by using a bimetallic Li−Cs base for deprotonation. Such alkali‐metallated frameworks are often precursors to other multimetallic frameworks with unique properties across different fields of science. [ABSTRACT FROM AUTHOR]

A methylation protocol of adamantane derivatives was investigated and optimized using AlCl3 and tetramethylsilane as the methylation agent. Substrates underwent exhaustive methylation of all available bridgehead positions with yields ranging from 62 to 86 %, and up to six methyl groups introduced in one step. Scaling‐up of the reaction was demonstrated by performing the >40 gram‐scale synthesis of 1,3,5,7‐tetramethyladamantane with 62 % yield. For several substrates, rearrangements were observed, as well as cleavage of functional groups or Csp3−Csp2 bonds or even cyclohexyl‐adamantyl bonds. Based on mechanistic studies, it is suggested that a reactive methylation complex is formed from tetramethylsilane and AlCl3. X‐ray diffraction structures of hexamethylated bis‐adamantyls reveal elongation or widening of sp3 carbon bonds between adamantyl moieties to 1.585(3) Å and 125.26(9)° due to repulsive H⋅⋅⋅H contacts. [ABSTRACT FROM AUTHOR]

The synthesis, crystal structure and spectroscopic and electronic properties of N‐(2‐methyl‐5‐nitrophenyl)‐4‐(pyridin‐2‐yl)pyrimidin‐2‐amine (NPPA), C16H13N5O2, a potential template for drug design against chronic myelogenous leukemia (CML), is reported. The design and construction of the target molecule were carried out starting from the guanidinium nitrate salt (previously synthesized) and the corresponding enaminone. X‐ray diffraction analysis and a study of the Hirshfeld surfaces revealed important interactions between the nitro‐group O atoms and the H atoms of the pyridine and pyrimidine rings. A crystalline ordering in layers, by the stacking of rings through interactions of the π–π type, was observed and confirmed by a study of the shape‐index surfaces and dispersion energy calculations. Quantitative electrostatic potential studies revealed the most positive value of the molecule on regions close to the N—H groups (34.8 kcal mol−1); nevertheless, steric impediments and the planarity of the molecule do not allow the formation of hydrogen bonds from this group. This interaction is however activated when the molecule takes on a new extended conformation in the active pocket of the enzyme kinase (PDB ID 2hyy), interacting with protein residues that are fundamental in the inhibition process of CML. The most negative values of the molecule are seen in regions close to the nitro group (−35.4 and −34.0 kcal mol−1). A molecular docking study revealed an energy affinity of ΔG = −10.3 kcal mol−1 for NPPA which, despite not having a more negative value than the control molecule (Imatinib; ΔG = −12.8 kcal mol−1), shows great potential to be used as a template for new drugs against CML. [ABSTRACT FROM AUTHOR]

CTLA‐4 is an essential regulator of T‐cell immune responses whose intracellular trafficking is a hallmark of its expression. Defects in CTLA‐4 trafficking due to LRBA deficiency cause profound autoimmunity in humans. CTLA‐4 rapidly internalizes via a clathrin‐dependent pathway followed by poorly characterized recycling and degradation fates. Here, we explore the impact of manipulating Rab GTPases and LRBA on CTLA‐4 expression to determine how these proteins affect CTLA‐4 trafficking. We observe that CTLA‐4 is distributed across several compartments marked by Rab5, Rab7 and Rab11 in both HeLa and Jurkat cells. Dominant negative (DN) inhibition of Rab5 resulted in increased surface CTLA‐4 expression and reduced internalization and degradation. We also observed that constitutively active (CA) Rab11 increased, whereas DN Rab11 decreased CTLA‐4 surface expression via an impact on CTLA‐4 recycling, indicating CTLA‐4 shares similarities with other recycling receptors such as EGFR. Additionally, we studied the impact of manipulating both LRBA and Rab11 on CTLA‐4 trafficking. In Jurkat cells, LRBA deficiency was associated with markedly impaired CTLA‐4 recycling and increased degradation that could not be corrected by expressing CA Rab11. Moreover LRBA deficiency reduced CTLA‐4 colocalization with Rab11, suggesting that LRBA is upstream of Rab11. These results show that LRBA is required for effective CTLA‐4 recycling by delivering CTLA‐4 to Rab11 recycling compartments, and in its absence, CTLA‐4 fails to recycle and undergoes degradation. [ABSTRACT FROM AUTHOR]

Exploiting cooperative effects between Na and FeII centres present in tris(amide) ferrate complexes has led to the chemoselective ferration of pentafluorobenzene, benzene, toluene, anisole, and pyridine being realised at room temperature. The importance of this bimetallic partnership is demonstrated by neither the relevant sodium amide (NaHMDS or NaTMP) nor the FeII amide Fe(HMDS)2 efficiently metallating these substrates under the conditions of this study. By combining NMR studies with the isolation of key intermediates and DFT calculations, we offer a possible mechanism for how these reactions take place, uncovering a surprising reaction pathway in which the metals cooperate in a synchronised manner. Although the isolated products are formally the result of Fe‐H exchange, theoretical calculations indicate that the aromatic substrates undergo Na‐H exchange followed by fast intramolecular transmetallation to Fe, thus stabilizing the newly generated aryl fragment. [ABSTRACT FROM AUTHOR]

Though s‐block organometallics are indispensable tools in synthetic chemistry, their impact in homogeneous catalysis has been small compared to that for transition metals. Surprisingly, however, Group 1 and 2 compounds have recently been utilised in hydroelementation catalysis. For example, transfer hydrogenation of alkenes to alkanes has been catalysed by Group 2 (Ca, Sr, Ba) bis‐hexamethyldisilazides (HMDS), though reactions failed with magnesium. Stimulated by the knowledge that alkali metals can mediate applications of other compounds, this study reports successful catalytic transfer hydrogenation of alkenes with magnesium bis‐hexamethyldisilazide when combined with alkali metals in heterobimetallic complexes. By screening all Group 1 metals (Li−Cs), the efficiency of these catalyses gives an indication of the relative power of the synergistic effect exerted on magnesium by the alkali metal. The Cs−Mg partnership shows the best efficiency with styrene, while K−Mg works best with 1,1‐diphenylethylene. [ABSTRACT FROM AUTHOR]

Focusing mainly on sodium 2‐ethylhexanoate, this study reveals that the carboxylate exists as a dimer in MeOD solution as evidenced by Diffusion Ordered NMR SpectroscopY (DOSY). Two crystalline varieties with distinct polymeric structures have been synthesised and crystallographically characterised. A mixed 1,10‐phenanthroline–water solvate [{(C5H10)(C2H5)COONa.(H2O)[1,10‐phen]}2]∞ contains dimeric [Na(OH2)]2 subunits, which propagate through hydrogen bonds between O atoms of the carboxylate and OH water bonds. Adjacent polymeric chains interdigitate with each other through π−π interactions between 1,10‐phen rings. Solvent‐free sodium 2‐ethylhexanoate has five‐coordinate cations comprising one bidentate chelating and three monodentate carboxylate oxygen atoms. Here, the packing arrangement is different with the central hydrophilic (NaO2)∞ core surrounded by a wrapping of disordered alkyl groups. A similar polymeric structure is observed for the crystalline DMSO‐solvated sodium valproate [{(C3H7)(C4H8)COONa.(DMSO)}]∞. This adopts a layered arrangement comprising alternating sodium carboxylate hydrophilic layers and hydrophobic organic bilayers. [ABSTRACT FROM AUTHOR]

Bimetallic complexes combining an alkali‐metal with a lower electropositive metal have demonstrated unique chemical profiles which can be rationalised in terms of chemical cooperativity. Advancing the rational design of these types of complexes, a adaptable method is described to prepare a new family of potassium metal(ates) containing the highly sterically demanding silyl(bis)amide {Ph2Si(NAr*)2}2− (Ar*=2,6‐diisopropylphenyl). Using a sequential deprotonative co‐complexation approach, mono‐metallation of Ph2Si(NHAr*)2 (1) is accomplished using potassium alkyl KCH2SiMe3 yielding [{Ph2Si(NHAr*)(NAr*)K}∞] (2), which, in turn, undergoes co‐complexation with the relevant M(CH2SiMe3)2 (M=Mg, Zn, Mn) enabling metallation of the remaining NHAr* group to furnish silylbis(amido) alkyl potassium metal(ates) [{Ph2Si(NAr*)2M(THF)x(CH2SiMe3)}−{K(THF)y}+] (M=Zn, x=0, y=4, 3; M=Mg, x=1, y=3, 4; and M=Mn, x=0, y=4, 5). Reactivity studies of potassium manganate 5 with the amine HMDS(H) (HMDS=N[SiMe3]2 revealed the kinetic activation of the remaining alkyl group on Mn furnishing [K(THF)2{Ph2Si(NAr*)2}Mn(HMDS)] (6). The structures of these bimetallic complexes along with that of the potassium precursor 2 have been established by X‐ray crystallographic studies. [ABSTRACT FROM AUTHOR]

The Grignard reagent, iPrMgCl and its lithium chloride‐enhanced 'turbo' derivative iPrMgCl⋅LiCl have been employed to investigate the single iodo/magnesium exchange reactions of the trisubstituted arenes, 2,5‐diiodo‐N,N‐diisopropylbenzamide 1, 1,4‐diiodo‐2‐methoxybenzene 2, and 1,4‐diiodo‐2‐(trifluoromethyl)benzene 3. These three arenes themselves were initially prepared by a double ortho‐, meta′‐deprotonation of N,N‐diisopropylbenzamide, anisole and (trifluoromethyl)benzene, respectively, using the sodium magnesiate reagent [Na4Mg2(TMP)6(nBu)2] (where TMP is 2,2,6,6‐tetramethylpiperidide), and subsequent electrophilic quenching with iodine/THF solution. Thus, by following a combined deprotonation and magnesium/halogen exchange strategy, the simple monosubstituted arenes can be converted to trisubstituted diiodoarenes, which can ultimately be transformed into the corresponding mono‐magnesiated arenes, in THF at −40 °C, within seconds in good yields. The other functional group (OMe, NiPr2 or CF3 respectively) present on the di‐iodoarenes helps direct the exchange reaction to the ortho position, whereas subsequent addition of different electrophiles permits the preparation of hetero‐poly‐functional‐arenes, with three different substituents in their structure. Intriguingly, if water is used as the electrophile, a new and facile route to prepare meta‐substituted arenes, which cannot be easily obtained by conventional processes, is forthcoming. In contrast to directed ortho‐metalation (DoM) chemistry, this reaction sequence can be thought of as InDirect meta‐Metalation (IDmM). The scope of the chemistry has been tested further by exposing the initial unreacted iodo‐functionality at the meta‐position to a second Mg/I‐exchange reaction and subsequent functionalization. [ABSTRACT FROM AUTHOR]

Pairing lithium and manganese(II) to form lithium manganate [Li2Mn(CH2SiMe3)4] enables the efficient direct Mn–I exchange of aryliodides, affording transient (aryl)lithium manganate intermediates which in turn undergo spontaneous C−C homocoupling at room temperature to furnish symmetrical (bis)aryls in good yields under mild reaction conditions. The combination of EPR with X‐ray crystallographic studies has revealed the mixed Li/Mn constitution of the organometallic intermediates involved in these reactions, including the homocoupling step which had previously been thought to occur via a single‐metal Mn aryl species. These studies show Li and Mn working together in a synergistic manner to facilitate both the Mn–I exchange and the C−C bond‐forming steps. Both steps are carefully synchronized, with the concomitant generation of the alkyliodide ICH2SiMe3 during the Mn–I exchange being essential to the aryl homocoupling process, wherein it serves as an in situ generated oxidant. [ABSTRACT FROM AUTHOR]

Dialkylaluminium amides iBu2Al(TMP) and iBu2Al(HMDS) can perform catalytic hydroboration of ketones with pinacolborane to form the expected boronic esters. However, repeating the same reactions stoichiometrically without a ketone leads unexpectedly to ring‐opening of pinacolborane and insertion of its open chain into the Al−N(amido) bond. To date there has been limited knowledge on decomposition pathways of HBpin despite its prominent role in hydroboration chemistry. X‐ray crystallography shows these mixed Al−B products [iBu2Al{OC(Me)2C(Me)2O}B(H)(NR2)]2 (NR2=TMP or HMDS) form dimers with an (AlO)2 core and terminal B−N bonds. Since the bond retention (B−H) and bond breaking (B−O) in these transformations seemed surprising, DFT calculations run using M11/6‐31G(d,p) gave an energy profile consistent with a σ‐bond metathesis mechanism where London dispersion interactions between iBu and (amide) Me groups play an important stabilising role in the final outcome. [ABSTRACT FROM AUTHOR]

In 2019, American workers reported 26,221 claims of workplace harassment to the Equal Employment Opportunity Commission. Nearly half of those claims represented sex‐based harassment. The #MeToo movement has shined a spotlight on the pervasiveness of harassment across sectors and institutions. A 2018 report by the National Academies of Sciences, Engineering, and Medicine indicates that 58 percent of women in academic institutions, for instance, have experienced some form of sexual harassment. In this article, the authors propose a three‐part framework to establish a culture of zero tolerance of sexual harassment. The framework helps academic and other institutions prevent sexual harassment, protect victims from risks of reporting harassment, and set accountability measures to demand justice. The utility of the framework is twofold. First, administrators can apply it as a tool to audit institutional attitudes toward sexual harassment. Second, leaders can apply it as a corrective tool to prevent permissive organizational climates that allow sexual harassment to be perpetuated. [ABSTRACT FROM AUTHOR]

A straightforward alkali‐metal‐mediated hydroamination of styrenes using biorenewable 2‐methyltetrahydrofuran as a solvent is reported. Refuting the conventional wisdom of the incompatibility of organolithium reagents with air and moisture, shown here is that the presence of moisture is key in favoring formation of the target phenethylamines over competing olefin polymerization products. The method is also compatible with sodium amides, with the latter showing excellent promise as highly efficient catalysts under inert atmosphere conditions. [ABSTRACT FROM AUTHOR]

The structures of five s‐block metal salt forms of three disulfonated monoazo dyes are presented. These are poly[di‐μ‐aqua‐diaqua[μ4‐3,3′‐(diazane‐1,2‐diyl)bis(benzenesulfonato)]disodium(I)], [Na2(C12H8N2O6S2)(H2O)4]n, (I), catena‐poly[[tetraaquacalcium(II)]‐μ‐3,3′‐(diazane‐1,2‐diyl)bis(benzenesulfonato)], [Ca(C12H8N2O6S2)(H2O)4]n, (II), catena‐poly[[[diaquacalcium(II)]‐μ‐2‐(4‐amino‐3‐sulfonatophenyl)‐1‐(4‐sulfonatophenyl)diazenium] dihydrate], {[Na(C12H10N3O6S2)(H2O)2]·2H2O}n, (III), hexaaquamagnesium bis[2‐(4‐amino‐3‐sulfonatophenyl)‐1‐(4‐sulfonatophenyl)diazenium] octahydrate, [Mg(H2O)6](C12H10N3O6S2)2·8H2O, (IV), and poly[[{μ2‐4‐[2‐(4‐amino‐2‐methyl‐5‐methoxyphenyl)diazen‐1‐yl]benzene‐1,3‐disulfonato}di‐μ‐aqua‐diaquabarium(II)] dihydrate], {[Ba(C14H13N3O7S2)(H2O)4]·2H2O}n, (V). Compound (III) is that obtained on crystallizing the commercial dyestuff Acid Yellow 9 [74543‐21‐8]. The Mg species is a solvent‐separated ion‐pair structure and the others are all coordination polymers with bonds from the metal atoms to sulfonate groups. Compound (I) is a three‐dimensional coordination polymer, (V) is a two‐dimensional coordination polymer and both (II) and (III) are one‐dimensional coordination polymers. The coordination behaviour of the azo ligands and the water ligands, the dimensionality of the coordination polymers and the overall packing motifs of these five structures are contrasted to those of monosulfonate monoazo congers. It is found that (I) and (II) adopt similar structural types to those of monosulfonate species but that the other three structures do not. [ABSTRACT FROM AUTHOR]

With the aim of increasing the number of well‐defined alkali metal aluminates, six new crystalline examples containing heteroleptic tert‐butoxide – isobutyl ligand sets are reported. NMR spectroscopic studies in C6D6 solution have determined their common general formula [(iBu)2Al(OtBu)2AM·(D)], where AM = Li, D = 2 THF, TMEDA or PMDETA; AM = Na, D = TMEDA or PMDETA; and AM = K, D = PMDETA. X‐ray crystallographic studies show that despite the different sized alkali metals involved all six complexes adopt a common dinuclear motif with [AlO(AM)O] ring cores. Though Al–OtBu–Li linkages are common, the heavier alkali metal examples reported here are exceptionally rare. These structures could be interpreted as co‐complexes between monomeric forms of tBuO(AM) and (iBu)2Al(OtBu). [ABSTRACT FROM AUTHOR]

The need for alternative, complementary approaches to enable C−C bond formation within organic chemistry is an on‐going challenge in the area. Of particular relevance are transformations that proceed in the absence of transition‐metal reagents. In the current study, we report a comprehensive investigation of the coupling of nitrile imines and aryl boronic acids as an approach towards sustainable C−C bond formation. In situ generation of the highly reactive 1,3‐dipole facilitates a Petasis–Mannich‐type coupling via a nucleophilic boronate complex. The introduction of hydrazonyl chlorides as a complementary nitrile imine source to the 2,5‐tetrazoles previously reported by our laboratory further broadens the scope of the approach. Additionally, we exemplify for the first time the extension of this protocol into another 1,3‐dipole, through the synthesis of aryl ketone oximes from aryl boronic acids and nitrile N‐oxides. [ABSTRACT FROM AUTHOR]

We report the first transition metal catalyst‐ and ligand‐free conjugate addition of lithium tetraorganozincates (R4ZnLi2) to nitroolefins. Displaying enhanced nucleophilicity combined with unique chemoselectivity and functional group tolerance, homoleptic aliphatic and aromatic R4ZnLi2 provide access to valuable nitroalkanes in up to 98 % yield under mild conditions (0 °C) and short reaction time (30 min). This is particularly remarkable when employing β‐nitroacrylates and β‐nitroenones, where despite the presence of other electrophilic groups, selective 1,4 addition to the C=C is preferred. Structural and spectroscopic studies confirmed the formation of tetraorganozincate species in solution, the nature of which has been a long debated issue, and allowed to unveil the key role played by donor additives on the aggregation and structure of these reagents. Thus, while chelating N,N,N',N'‐tetramethylethylenediamine (TMEDA) and (R,R)‐N,N,N',N'‐tetramethyl‐1,2‐diaminocyclohexane (TMCDA) favour the formation of contacted‐ion pair zincates, macrocyclic Lewis donor 12‐crown‐4 triggers an immediate disproportionation process of Et4ZnLi2 into equimolar amounts of solvent‐separated Et3ZnLi and EtLi. [ABSTRACT FROM AUTHOR]

Previous studies of different solvates of 2‐methylpyridyllithium (2‐picolyllithium) have uncovered electronic structures corresponding to aza‐allyl and enamido resonance forms of the metallated pyridine‐based compounds. Here, we report the synthesis and characterization of [2‐CH2Li(THF)2C5H4N], a new THF solvate. X‐ray crystallographic studies reveal a dimeric arrangement featuring a non‐planar eight‐membered [NCCLi]2 ring, in which the primary cation‐anion interaction is between the central Li atom and the C atom of the deprotonated methyl group [length, 2.285(2) Å], suggesting a new carbanionic resonance structure for this 2‐picolyllithium series. The significant carbanionic character of [2‐CH2Li(THF)2C5H4N] was confirmed by gas‐phase DFT calculations [B3LYP/6‐311+G(d)] with the calculated electron density interrogated by means of quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. For comparison these computational analyses were also performed on the literature structures of [2‐CH2Li(2‐Picoline)C5H4N] and [2‐CH2Li(PMDETA)C5H4N]. In a reactivity study, [2‐CH2Li(THF)2C5H4N] was found to undergo nucleophilic addition to pyridine to generate dipyridylmethane in a good yield. [ABSTRACT FROM AUTHOR]

The US Army is replacing traditional munitions with insensitive munitions resistant to accidental detonation. Although the parent insensitive munition compound nitroguanidine (NQ) is generally not acutely toxic at concentrations >1000 mg/L in aquatic exposures, products formed by intensive ultraviolet (UV) degradation resulted in multiple‐order of magnitude increases in toxicity. A methylated congener of NQ, 1‐methyl‐3‐nitroguanidine (MeNQ), is also being assessed for potential use in insensitive munition explosive formulations; therefore, the present study investigated the hazard of parent versus UV‐degraded MeNQ using fathead minnows (Pimephales promelas). Although up to 716 mg/L parent MeNQ caused no significant mortality or effects on growth in larval P. promelas fish in 7‐d exposures, a similar concentration of MeNQ subjected to UV treatment resulted in 85% mortality. The UV treatment degraded only 3.3% of the MeNQ (5800 mg/L stock, UV‐treated for 6 h), indicating that MeNQ degradation products have potentially high toxicity. The parent MeNQ exposure caused significantly decreased transcriptional expression of genes within the significantly enriched insulin metabolic pathway, suggesting antagonism of bioenergetics pathways, which complements observed, although nonsignificant, decreases in body weight. Significant differential transcriptional expression in the UV‐degraded MeNQ treatments resulted in significant enrichment of pathways and functions related to the cell cycle, as well as erythrocyte function involved in O2/CO2 exchange. These functions represent potential mechanistic sources of increased toxicity observed in the UV‐degraded MeNQ exposures, which are distinct from previously observed mechanisms underlying increased toxicity of UV‐degraded NQ in fish. Environ Toxicol Chem 2020;39:612–622. © 2019 SETAC [ABSTRACT FROM AUTHOR]

Though alkali metal NacNac (β‐diketiminate) complexes have been utilised in synthesis as NacNac‐transfer agents, studies of them in their own right with small molecules are exceptionally rare. Here, the lithium compound of the common 2,6‐diisopropylphenyl‐β‐methyldiketiminate [NacNac(Dipp, Me)] ligand is investigated with carbon dioxide and isocyanates. In all four cases reaction occurs at the backbone γ‐C atom of the NacNac ligand, which redistributes electronically into a diimine. Insertion of CO2 gives an eight‐atom carboxylate (Li2O4C2) ring at the γ‐C site in a dimer. Insertion of tBuNCO gives a secondary amide at the γ‐C site in a monomer with TMEDA chelating lithium. Double insertion of tBuNCO and (adventitious) oxygen gives a dimer with a (LiO)2 central core involving the latter source. Insertion of less bulky (iPrNCO) gives a dimer with dimerisation through the C=O bonds of the emergent secondary amide function. [ABSTRACT FROM AUTHOR]