Patrick Pröhm

Herein, the ionic liquid [NEt ₃ Me][Cl(SO ₂ ) _n ] is reported as a reversible sulfur dioxide storage medium and transfer reagent for organic synthesis. Vapor pressure measurements revealed that the ionic liquid can store up to 3.66 equivalents of SO ₂ at room temperature, which can be released in a controlled manner upon heating or depressurization. The physicochemical properties were investigated, and long‐term stability was demonstrated, as no decomposition was observed for more than six months. Based on its solid‐state structure, the bonding analysis indicated a covalent sulfur‐chlorine interaction, which is consistent with conducted Raman studies and quantum chemical calculations. Atom economy and cost estimates are compared with those of commonly used SO ₂ surrogates, highlighting the developed transfer reagent as an inexpensive and (atom‐)economic alternative for laboratory‐scale applications. The synthetic utility of [NEt ₃ Me][Cl(SO ₂ ) _n ] is further demonstrated, enabling the synthesis of valuable organosulfur compounds such as 3‐sulfolenes, sulfonamides, sulfones, and sulfonyl fluorides in good to excellent yields. Importantly, the incorporation of SO ₂ is scalable, rendering [NEt ₃ Me][Cl(SO ₂ ) _n ] as a safe and user‐friendly SO ₂ transfer reagent for synthetic applications.

The reaction of tetraethylammonium polychlorides or polybromides in propionitrile with substoichiometric amounts of diluted fluorine at low temperatures leads to the non-classical interhalogen compounds [NEt₄]­[F­(X₂)₃] (X = Cl and Br). These compounds are the first examples of anions containing a central μ₆ fluoride anion, which is octahedrally surrounded by Br₂ or Cl₂ units, respectively. Single-crystal X-ray diffraction revealed that these compounds crystallize in the cubic system with every fluoride anion bridged by halogen units, resulting in a 3D network. Furthermore, single-crystal Raman and IR spectra were measured, and investigations using solid-state calculations were carried out.

CS2 promises easy access to degradable sulfur-rich polymers and insights into how main-group derivatisation affects polymer formation and properties, though its ring-opening copolymerisation is plagued by low linkage selectivity and small-molecule by-products. We demonstrate that a cooperative Cr(III)/K catalyst selectively delivers poly(dithiocarbonates) from CS2 and oxetanes while state-of-the-art strategies produce linkage scrambled polymers and heterocyclic by-products. The formal introduction of sulfur centres into the parent polycarbonates results in a net shift of the polymerisation equilibrium towards, and therefore facilitating, depolymerisation. During copolymerisation however the catalyst enables near quantitative generation of the metastable polymers in high sequence selectivity by limiting the lifetime of alkoxide intermediates. Furthermore, linkage selectivity is key to obtain semi-crystalline materials that can be moulded into self-standing objects. Our report demonstrates the potential of cooperative catalysis to produce previously inaccessible main-group rich materials with beneficial chemical and physical properties

We present the first structural evidence of mono- and bis(pyridine) chloronium cations. The latter was synthesized from a mixture of pyridine, elemental chlorine and sodium tetrafluoroborate in propionitrile at low temperatures. The mono(pyridine) chloronium cation was realized with the less reactive pentafluoropyridine, using ClF, AsF₅, and C₅F₅N in anhydrous HF. During the course of this study, we also investigated pyridine dichlorine adducts and found a surprising disproportionation reaction of chlorine that depended on the substitutional pattern of the pyridine. Electron richer dimethylpyridine (lutidine) derivatives favor a full disproportionation into a positively and a negatively charged chlorine atom which forms a trichloride monoanion, while unsubstituted pyridine forms a 1:1 py∙Cl₂ adduct.

A sequence selective ring-opening terpolymerisation of epoxides with CS₂ and phthalic thioanhydride yielding poly(ester-alt-ester-alt-trithiocarbonates) is reported.

A systematic study of halogenate(I/III) anions with polyatomic ligands is presented. The bis(perfluoro‐tert‐butoxy) halogenates(I) [X(OC₄F₉)₂]⁻, 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. Additionally, the bonding situation of the species in question are analyzed and discussed. Furthermore, the oxidation to the corresponding halogenate(III) derivatives was studied. For [Br(OC₄F₉)₂]⁻, oxidation with elemental fluorine gave [BrF₂(OC₄F₉)₂]⁻. Iodide was directly oxidized by ClOC₄F₉ to the I^III species [I(OC₄F₉)₄]⁻, which is a surprisingly inert anion that might be used as a weakly coordinating anion (WCA) in the future. For [Cl(OC₄F₉)₂]⁻, the decomposition products of the synthetic approaches towards a chlorine(III) system were analyzed.

The [F(ClF)₃]⁻ anion was synthesized from an organic chloride salt and chlorine monofluoride. Comparison between the [F(ClF)₃]⁻ anion and other permutated chlorine fluorine heptahalides reveals the unique effect of a central fluoride ion.

We present a facile synthesis of the soluble fluoridobromates [NEt₃Me][BrF₄] and [NEt₃Me][Br₂F₇] via fluorination of the corresponding bromide salts in acetonitrile, propionitrile or bromine. We structurally characterized the [BrF₂]^– anion, an intermediate during the synthesis, for the first time. Additionally, the dissolution of noble metals to form the corresponding halometallates as well as the application of [NEt₃Me][BrF₄] as a fluorination agent for disulfides to form pentafluorosulfanyls was studied.

Perchlorinated and perbrominated organic dications [C ₁₀ Cl ₁₀ ] ²⁺ and [C ₁₀ Br ₁₀ ] ²⁺ have been obtained instead of monomeric cyclopentadienyl cations C ₅ Cl ₅ ⁺ and C ₅ Br ₅ ⁺ .

A facile one‐pot gram‐scale synthesis of tetraalkylammonium tetrafluoridochlorate(III) [cat][ClF₄] ([cat]=[NEt₃Me]⁺, [NEt₄]⁺) is described. An acetonitrile solution of the corresponding alkylammonium chloride salt is fluorinated with diluted fluorine at low temperatures. The reaction proceeds via the [ClF₂]⁻ anion which is structurally characterized for the first time. The potential application of [ClF₄]⁻ salts as fluorinating agents is evaluated by the reaction with diphenyl disulfide, Ph₂S₂, to pentafluorosulfanyl benzene, PhSF₅. The CN moieties in acetonitrile and [B(CN)₄]⁻ are transferred in CF₃ groups. Exposure of carbon monoxide, CO, leads to the formation of carbonyl fluoride, COF₂, and elemental gold is dissolved under the formation of tetrafluoridoaurate [AuF₄]⁻.