Rethinking Chlorine: Essential Chemical or Replaceable Risk?

This review critically examines the dual nature of chlorine as both an indispensable base chemical and a potential risk. Chlorine and its byproduct hydrogen chloride play essential roles in the production of pharmaceuticals, plastics, agrochemicals, and disinfectants. However, their inherent toxicity, risks of handling, and environmental impacts necessitate a reassessment of their use and sustainability.

Polyethyleneimine-Based Cryogels Enabling the Selective and Reversible Adsorption of Chlorine.

Herein hyperbranched polyethyleneimine (hPEI) cryogels are reported for the selective and reversible adsorption of elemental chlorine. The cryogels are prepared in an aqueous solution by crosslinking with glutaraldehyde at subzero temperatures. The final macroporous composites bearing ammonium chloride groups are obtained after freeze-drying.

A polychloride-enabled synthesis of [NEtMe][PCl] serving as a potential PCl-storage and PCl-reagent.

Reaction of the ionic liquid [NEtMe][Cl] with white phosphorus (P) gives, quantitatively, hexachlorophosphate [NEtMe][PCl]. This compound shows similar reactivity as PCl, as confirmed for the reaction with phenol, carboxylic acids and ammonium chloride. At elevated temperature, [NEtMe][PCl] releases PCl and can therefore be used as a potential PCl-storage material.

Silver(i) Perfluoroalcoholates: Synthesis, Structure, and their Use as Transfer Reagents.

Herein we report a general access to silver(i) perfluoroalcoholates, their structure in the solid state and in solution, and their use as transfer reagents. The silver(i) perfluoroalcoholates are prepared by the reaction of AgF with the corresponding perfluorinated carbonyl compounds in acetonitrile and are stable for a prolonged time at -18 °C. X-ray analysis of single crystals of perfluoroalcoholate species showed that two Ag(i) centers are bridged by the alcoholate ligands.

Bichloride-based ionic liquids for the merged storage, processing, and electrolysis of hydrogen chloride.

Hydrogen chloride is produced as a by-product in industrial processes on a million-ton scale. Since HCl is inherently dangerous, its storage and transport are avoided by, e.g.

Catalyst-Free Trifluoromethoxylation of Silyl Enol Ethers and Allyl Silanes with Bis(trifluoromethyl)peroxide.

Radical trifluoromethoxylation is an attractive approach to prepare compounds featuring the important OCF group, however most existing methods have focused on aromatic substrates. Here, we report novel methodologies with alkenyl substrates employing bis(trifluoromethyl)peroxide (BTMP) as a practical and comparatively atom economical trifluoromethoxylating reagent. With silyl enol ether substrates, switching reaction solvent allows for the synthesis of either α-(trifluoromethoxy)ketone products or unprecedented alkenyl-OCF species.

Reactivity of [AuF (SIMes)]: Pathway to Unprecedented Structural Motifs.

We report on a comprehensive reactivity study starting from [AuF (SIMes)] to synthesize different motifs of monomeric gold(III) fluorides. A plethora of different ligands has been introduced in a mono-substitution yielding trans-[AuF X(SIMes)] including alkynido, cyanido, azido, and a set of perfluoroalkoxido complexes. The latter were better accomplished via use of perfluorinated carbonyl-bearing molecules, which is unprecedented in gold chemistry.

The Rise of Trichlorides Enabling an Improved Chlorine Technology.

Chlorine plays a central role for the industrial production of numerous materials with global relevance. More recently, polychlorides have been evolved from an area of academic interest to a research topic with enormous industrial potential. In this minireview, the value of trichlorides for chlorine storage and chlorination reactions are outlined.

Gold Teflates Revisited: From the Lewis Superacid [Au(OTeF ) ] to the Anion [Au(OTeF ) ].

A new synthetic access to the Lewis acid [Au(OTeF ) ] and the preparation of the related, unprecedented anion [Au(OTeF ) ] with inorganic or organic cations starting from commercially available and easy-to-handle gold chlorides are presented. In this first extensive study of the Lewis acidity of a transition-metal teflate complex by using different experimental and quantum chemical methods, [Au(OTeF ) ] was classified as a Lewis superacid. The solid-state structure of the triphenylphosphine oxide adduct [Au(OPPh )(OTeF ) ] was determined, representing the first structural characterization of an adduct of this highly reactive [Au(OTeF ) ].

Synthesis of a Hexachloro Sulfate(IV) Dianion Enabled by Polychloride Chemistry.

The preparation and structural characterization of [NEt Me] [SCl ] is described, which is the first example of a [SCl ] dianion and of a halosulfate anion of the type [S X ] in general. This dianion belongs to the group of 14-valence electron AB E systems and forms an octahedral structure in the solid-state. Interestingly, co-crystallization with CH Cl affords [NEt Me] [SCl ]⋅4 CH Cl containing [SCl ] dianions with C symmetry.

Synthesis of 3--Hypatulin B Featuring a Late-Stage Photo-Oxidation in Flow.

A synthesis of 3--hypatulin B, a highly oxygenated and densely functionalized bicyclic scaffold, is reported. The carbon skeleton was prepared by functionalization of a cyclopentanone and an intramolecular Mukaiyama aldol reaction. Highlights include a late-stage photo-oxidation of a methoxyallene to provide an ester group.

(Noble Gas) -NC Molecular Ions in Noble Gas Matrices: Matrix Infrared Spectra and Electronic Structure Calculations.

An investigation of pulsed-laser-ablated Zn, Cd and Hg metal atom reactions with HCN under excess argon during co-deposition with laser-ablated Hg atoms from a dental amalgam target also provided Hg emissions capable of photoionization of the CN photo-dissociation product. A new band at 1933.4 cm in the region of the CN and CN gas-phase fundamental absorptions that appeared upon annealing the matrix to 20 K after sample deposition, and disappeared upon UV photolysis is assigned to (Ar) CN , our key finding.

Investigation of Bis(Perfluoro-tert-Butoxy) Halogenates(I/III).

A systematic study of halogenate(I/III) anions with polyatomic ligands is presented. The bis(perfluoro-tert-butoxy) halogenates(I) [X(OC F ) ] , X=Cl, Br, I, of chlorine, bromine, and iodine are prepared as their tetraethylammonium salts and characterized with IR, Raman, and NMR spectroscopic methods, as well as single-crystal X-ray diffraction analyses. Spectroscopical data are supported by quantum-chemical calculations.

Novel synthetic pathway for the production of phosgene.

Chloride ions are efficient catalysts for the synthesis of phosgene from carbon monoxide and elemental chlorine at room temperature and atmospheric pressure. Control experiments rule out a radical mechanism and highlight the role of triethylmethylammonium trichloride, [NEtMe][Cl], as active species. In the catalytic reaction, commercially available [NEtMe]Cl reacts with Cl to form [NEtMe][Cl], enabling the insertion of CO into an activated Cl─Cl bond with a calculated energy barrier of 56.

Synthesis of Plakortolides E and I Enabled by Base Metal Catalysis.

A protecting-group-free synthesis of two endoperoxide natural products, plakortolide E and plakortolide I, is reported. Key steps are a vanadium-mediated epoxidation, an iron-catalyzed allylic substitution, and a cobalt-induced endoperoxide formation. Our approach combines chemoselective bond-forming reactions and one-pot operations to forge an overall efficient synthesis.

Conductivity and Redox Potentials of Ionic Liquid Trihalogen Monoanions [X ] , [XY ] , and [BrF ] (X=Cl, Br, I and Y=Cl, Br).

The ionic liquid (IL) trihalogen monoanions [N ][X ] and [N ][XY ] ([N ] =triethylmethylammonium, X=Cl, Br, I, Y=Cl, Br) were investigated electrochemically via temperature dependent conductance and cyclic voltammetry (CV) measurements. The polyhalogen monoanions were measured both as neat salts and as double salts in 1-butyl-1-methyl-pyrrolidinium trifluoromethane-sulfonate ([BMP][OTf], [X ] /[XY ] 0.5 M).

Synthesis and Characterization of Poly(hydrogen halide) Halogenates (-I).

Herein, we report the synthesis and characterization of a variety of novel poly(hydrogen halide) halogenates (-I). The bifluoride ion, which is known to have the highest hydrogen bond energy of ≈160 kJ mol , is the most famous among many examples of [X(HX) ] anions (X=F, Cl) known in the literature. In contrast, little is known about poly(hydrogen halide) halogenates containing two different halogens, ([X(HY) ] ).

Friedel-Crafts Type Methylation with Dimethylhalonium Salts.

The dimethylchloronium salt [Me Cl][Al(OTeF ) ] is used to methylate electron-deficient aromatic systems in Friedel-Crafts type reactions as shown by the synthesis of N-methylated cations, such as [MeNC F ] , [MeNC F I] , and [MeN C F ] . To gain a better understanding of such fundamental Friedel-Crafts reactions, the role of the dimethylchloronium cation has been evaluated by quantum-chemical calculations.

In Situ Synthesis and Applications for Polyinterhalides Based on BrCl.

The use of neat BrCl in organic and inorganic chemistry is limited due to its gaseous aggregate state and especially its decomposition into Cl and Br . The stabilization of BrCl in form of reactive ionic liquids via a novel in situ synthesis route shifts this equilibrium drastically to the BrCl side, which leads to safer and easier-to-handle interhalogenation reagents. Furthermore, the crystalline derivatives of the hitherto unknown [Cl(BrCl) ] and [Cl(BrCl) ] anions were synthesized and characterized by single-crystal X-ray diffraction (XRD), Raman and IR spectroscopy, as well as quantum chemical calculations.

[NMe ][I Br ]: A new Iodobromide from an Ionic Liquid with Halogen-Halogen Interactions.

Tetramethylammonium tetraiodopentabromide [NMe ][I Br ] was the first iodobromide to be synthesized and crystallized in an ionic liquid as well as in dichloromethane. The new iodobromides show different structure motives yet are unknown from other nonahalides and can be better described as [(I Br ) ⋅2 IBr]. The additional IBr units are connected by halogen-halogen interactions on the central V-shaped [I Br ] .