Competitive Salt Precipitation/Dissolution During Free‐Water Reduction in Water‐in‐Salt Electrolyte

Water‐in‐salt electrolytes based on highly concentrated bis(trifluoromethyl)sulfonimide (TFSI) promise aqueous electrolytes with stabilities nearing 3 V. However, especially with an electrode approaching the cathodic (reductive) stability, cycling stability is insufficient. While stability critically relies on a solid electrolyte interphase (SEI), the mechanism behind the cathodic stability limit remains unclear. Now, two distinct reduction potentials are revealed for the chemical environments of free and bound water and that both contribute to SEI formation. Free water is reduced about 1 V above bound water in a hydrogen evolution reaction (HER) and is responsible for SEI formation via reactive intermediates of the HER; concurrent LiTFSI precipitation/dissolution establishes a dynamic interface. The free‐water population emerges, therefore, as the handle to extend the cathodic limit of aqueous electrolytes and the battery cycling stability.     

On the Importance of Decarbonylation as a Side‐Reaction in the Ruthenium‐Catalysed Dehydrogenation of Alcohols: A Combined Experimental and Density Functional Study

We report a density functional study (B97‐D2 level) of the mechanism(s) operating in the alcohol decarbonylation that occurs as an important side‐reaction during dehydrogenation catalysed by [RuH₂(H₂)(PPh₃)₃]. By using MeOH as the substrate, three distinct pathways have been fully characterised involving either neutral tris‐ or bis‐phosphines or anionic bis‐phosphine complexes after deprotonation. α‐Agostic formaldehyde and formyl complexes are key intermediates, and the computed rate‐limiting barriers are similar between the various decarbonylation and dehydrogenation paths. The key steps have also been studied for reactions involving EtOH and iPrOH as substrates, rationalising the known resistance of the latter towards decarbonylation. Kinetic isotope effects (KIEs) were predicted computationally for all pathways and studied experimentally for one specific decarbonylation path designed to start from [RuH(OCH₃)(PPh₃)₃]. From the good agreement between computed and experimental KIEs (observed k_H/k_D=4), the rate‐limiting step for methanol decarbonylation has been ascribed to the formation of the first agostic intermediate from a transient formaldehyde complex.     

Radical cyclization of α-bromo aluminum acetals onto alkenes and alkynes (radic[Al] process): a simple access to γ-lactols and 4-methylene-γ-lactols

An efficient preparation of γ-lactols and methylene-γ-lactols is described. Highly acid-sensitive lactols are prepared in a concise manner by using a radical cyclization of aluminum acetals. The precursors for the radical reactions are readily prepared from allyl or propargyl alcohols and α-bromo acids. Functionalization of the resulting γ-lactols and methylene-γ-lactols can be achieved following isolation, leading to synthetically useful building blocks, such as 1,4-diols, 1,4-dienes, γ-lactones, and polysubstituted tetrahydrofurans.     

Triaryl-1,3,5-triazinane-2,4,6-triones (Isocyanurates) Peripherally Functionalized by Donor Groups: Synthesis and Study of Their Linear and Nonlinear Optical Properties

The linear optical (LO) and nonlinear optical (NLO) properties of a series of isocyanurates functionalized by donor arms at the periphery are reported herein. These octupolar derivatives were obtained in a straightforward way from commercial isocyanate derivatives and were fully characterized. Although several of these compounds are known, those that exhibited the largest NLO activities are all new compounds. In terms of second-order activity, several of these derivatives exhibit remarkable activity/transparency tradeoffs. In terms of third-order activity, the longer derivatives with the stronger donor groups (X=NH(2) , NMe(2) , or NPh(2) ) were shown to possess significant two-photon absorption cross sections. These strongly luminescent derivatives exhibit two-photon absorption cross sections up to 410?GM. DFT computations were also conducted to unravel their electronic structures and to rationalize their NLO properties. To our knowledge, the present study is the first concerned with the nonlinear optical properties of these original cyclotrimers.     

Direct involvement of the acetato ligand in the reductive elimination step of rhodium-catalyzed methanol carbonylation

For the last step of rhodium-catalyzed methanol carbonylation, high-pressure NMR, and kinetic and experimental data supported by density functional theory calculations are consistent with substitution of I(-) by an AcO(-) ligand on the [RhI(3)(COCH(3))(CO)(2)](-) species followed by reductive elimination of acetic anhydride, which immediately reacts with water to afford acetic acid.     

Highly active zinc alkyl cations for the controlled and immortal ring-opening polymerization of ε-caprolactone

Zinc alkyl cations supported by N,N-BIAN-type bidentate ligands were found to be highly active in the immortal ROP of ε-caprolactone to yield narrowly disperse and chain length-controlled poly(ε-caprolactone), whether in solution or bulk polymerization conditions.     

Triaryl-1,3,5-triazinane-2,4,6-triones functionalized with electron-rich Fe(II) and Ru(II) acetylide complexes: new organometallic octupoles with large hyperpolarizabilities

The synthesis and study of a series of trinuclear organometallic triaryl-1,3,5-triazinane-2,4,6-triones functionalized by d(6)-transition metal acetylides complexes at their periphery are reported. Remarkably large hyperpolarizabilities, far superior to those of related purely organic derivatives, are measured by hyper-Rayleigh scattering (HRS) for these new octupolar chromophores.     

Effect on pKa of metal-bound water molecules in lanthanide ion-induced cyclen "cavities"

[reaction: see text] The macrocyclic cyclen conjugates 1-4 were synthesized with the aim of forming lanthanide ion-based macrocyclic conjugates possessing deep cavities, formed upon complexation to various lanthanide ions. These complexes all possess metal-bound water molecules, where the pKa of the water molecules depends on the nature of the cavity.     

Grignard reagent-promoted 6-endo-dig cyclization: instantaneous synthesis of original dipyrido[1,2-a:3′,4′-d]imidazole

Dipyrido[1,2-a:3′,4′-d]imidazole derivatives can be readily synthetized from various 3-alkyne-2-cyanoimidazo[1,2-a]pyridines via an efficient Grignard reagent-promoted 6-endo-dig cyclization of nitrile to alkynes. A previous optimization of the Sonogashira coupling reaction at C(3) of the 2-cyanoimidazo[1,2-a]pyridine was necessary as this coupling reaction is known to be largely influenced by the nature of the 2-substituent.