Synthesis and reactivity of fluorinated triaryl aluminum complexes

The addition of the Grignard 3,4,5-ArFMgBr to aluminum(III) chloride in ether generates the novel triarylalane Al(3,4,5-ArF)3·OEt2. Attempts to synthesize this alane via transmetalation from the parent borane with trimethylaluminum gave a dimeric structure with bridging methyl groups, a product of partial transmetalation. On the other hand, the novel alane Al(2,3,4-ArF)3 was synthesized from the parent borane and trimethylaluminum. Interestingly, the solid-state structure of Al(2,3,4-ArF)3 shows an extended chain structure resulting from neighboring Al···F contacts. Al(3,4,5-ArF)3·OEt2 was then found to be an effective catalyst for the hydroboration of carbonyls, imines, and alkynes with pinacolborane

Supramolecular aggregation in dithia-arsoles: chlorides, cations and N-centred paddlewheels

The benzo-fused dithia-chloro-arsole derivative C6H4S2AsCl (1) is found to crystallise in the triclinic space group P[1 with combining macron] with 17 molecules in the asymmetric unit whereas the tolyl derivative, MeC6H3S2AsCl (2) is polymorphic with the α-phase crystallising in the monoclinic space group P21/c with a single molecule in the asymmetric unit and the β-phase adopting a triclinic structure with two molecules in the asymmetric unit. Reaction of these dithia-chloro-arsole derivatives with LiN(SiMe3)2 in a 3 : 1 mole ratio afforded the unique paddlewheel structure (MeC6H4S2As)3N (4)

Metal-free tandem rearrangement/lactonization: Access to 3,3-disubstituted benzofuran-2-(3H)-ones

A novel metal‐free synthesis of 3,3‐disubstituted benzofuran‐2(3H)‐ones from the reaction between α‐aryl‐α‐diazoacetates and triarylboranes is presented. Initially, triarylboranes were successfully investigated in α‐arylations of α‐diazoacetates, however in the presence of an ortho‐heteroatom substituent the boron enolate intermediate undergoes an intramolecular rearrangement to form a quaternary center. The intermediate cyclizes affording valuable 3,3‐disubstituted benzofuranones in good yield

Diazaphospholene and diazaarsolene derived homogeneous catalysis

The past 20 years has seen significant advances in main group chemistry and their use in catalysis. This minireview showcases the recent emergence of phosphorus and arsenic containing heterocycles as catalysts. With that, we discuss how the Group 15 compounds diazaphospholenes, diazaarsolenes, and their cationic counterparts have proven to be highly effective catalysts for a wide range of reduction transformations. This minireview highlights how the initial discovery by Gudat of the hydridic nature of the P–H bond in these systems led to these compounds being used as catalysts, and discusses the wide range of examples currently present in the literature

Structure-property-reactivity studies on dithiaphospholes

The reaction of either toluene-3,4-dithiol or benzene dithiol with phosphorus(III) trihalides generates the corresponding benzo-fused 1,3,2-dithiaphospholes, RC6H3S2PX (R = Me (1), R = H (2); X = Cl, Br, I). The P-chloro-dithiaphospholes undergo: (a) halogen abstraction reactions with Lewis acids forming phosphenium cations; (b) substitution with LiHMDS base and; (c) reduction chemistry with sodium metal to generate the P–P σ-bonded dimer, (RC6H3S2P)2. Reduction catalysis of aldehydes with pinacolborane using dithiaphospholes is compared with their dioxaphosphole and diazaphosphole counterparts as precatalysts, revealing interesting differences in the reactivity of this series of compounds

Push and pull: the potential role of boron in N2 activation

Recent developments in main group chemistry towards the activation and conversion of N2 have lead to the revelation that boron can greatly affect these processes. Boron is capable of acting both as a borane Lewis acid to activate metal–N2 complexes and as an ambiphilic borylene able to activate free N2. The latter example is capable of both accepting and donating electron density in a manner reminiscent of transition metal systems containing both filled and empty d-orbitals

Investigations into the photophysical and electronic properties of pnictoles and Their pnictenium counterparts

The reaction of phosphole/arsole starting materials with a series of halide abstraction reagents afforded their respective phosphenium/arsenium complexes. UV–vis absorption and luminescence studies on these cations showed interesting emission profiles, which were found to be dependent upon counterion choice. The addition of a reductant to the phosphole reagent garnered a dimeric species with a central P–P bond, which when heated was found to undergo homolytic bond cleavage to produce an 11π radical complex. Electron paramagnetic resonance (EPR), supported by density functional theory (DFT) calculations, was used to characterize this radical species

Aluminium-catalysed isocyanate trimerization, enhanced by exploiting a dynamic coordination sphere

Main-group metals are inherently labile, hindering their use in catalysis. We exploit this lability in the synthesis of isocyanurates. For the first time we report a highly active catalyst that trimerizes alkyl, allyl and aryl isocyanates, and di-isocyanates, with low catalyst loadings under mild conditions, using a hemi-labile aluminium-pyridyl-bis(iminophenolate) complex

2021 roadmap for sodium-ion batteries

Abstract: Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid–electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology