Synthesis and Structural Characterization of Tetraalkylammonium Salts of the Weakly Coordinating Anion [Al(OTeF5)4]–

The weakly coordinating properties of the [Al(OTeF5)4]– anion were studied by the synthesis and characterization of its tetraalkylammonium salts [NAlk4][Al(OTeF5)4] [Alk4 = –(CH3)4, –(C2H5)4, –(C2H5)3CH3, –(C3H7)4, –(C4H9)4]. The one‐pot synthesis includes formation of the Brønsted acid in 1,2–difluorobenzene, H[Al(OTeF5)4](solv.), and its reaction with [NAlk4]Cl [Alk4 = –(CH3)4, –(C2H5)4, –(C2H5)3CH3, –(C3H7)4, –(C4H9)4] to the corresponding salts. Single crystals were obtained for [N(C4H9)4][Al(OTeF5)4] and characterized by X‐ray diffraction analysis

Insights on the Lewis Superacid Al(OTeF5)3: Solvent Adducts, Characterization and Properties

Preparation and characterization of the dimeric Lewis superacid [Al(OTeF5)3]2 and various solvent adducts is presented. The latter range from thermally stable adducts to highly reactive, weakly bound species. DFT calculations on the ligand affinity of these Lewis acids were performed in order to rank their remaining Lewis acidity. An experimental proof of the Lewis acidity is provided by the reaction of solvent‐adducts of Al(OTeF5)3 with [PPh4][SbF6] and OPEt3, respectively. Furthermore, their reactivity towards chloride and pentafluoroorthotellurate salts as well as (CH3)3SiCl and (CH3)3SiF is shown. This includes the formation of the dianion [Al(OTeF5)5]2−

[P4H]+[Al(OTeF5)4]−: protonation of white phosphorus with the Brønsted superacid H[Al(OTeF5)4](solv)

A sustainable transformation of white phosphorus (P4) into chemicals of higher value is one of the key aspects in modern phosphorus research. Even though the chemistry of P4 has been investigated for many decades, its chemical reactivity towards the simplest electrophile, the proton, is still virtually unknown. Based on quantum-chemical predictions, we report for the first time the successful protonation of P4 by the Brønsted acid H[Al(OTeF5)4](solv). Our spectroscopic results are in agreement with acid-mediated activation of P4 under protonation of an edge of the P4-tetrahedron and formation of a three-center two-electron P–H–P bond. These investigations are of fundamental interest as they permit the activation of P4 with the simplest electrophile as a new prototype reaction for this molecule

Discoveries and challenges en route to swinhoeisterol A

In this work, a full account of the authors’ synthetic studies is reported that culminated in the first synthesis of 13(14→8),14(8→7)diabeo‐steroid swinhoeisterol A as well as the related dankasterones A and B, 13(14→8)abeo‐steroids, and periconiastone A, a 13(14→8)abeo‐4,14‐cyclo‐steroid. Experiments are described in detail that provided further insight into the mechanism of the switchable radical framework reconstruction approach. By discussing failed strategies and tactics towards swinhoeisterol A, the successful route that also allowed an access to structurally closely related analogues, such as Δ22‐24‐epi‐swinhoeisterol A, is eventually presented

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−1, is the most famous among many examples of [X(HX)n]− anions (X=F, Cl) known in the literature. In contrast, little is known about poly(hydrogen halide) halogenates containing two different halogens, ([X(HY)n]−). In this work we present the synthesis of anions of the type [X(HY)n]− (X=Br, I, ClO4; Y=Cl, Br, CN) stabilized by the [PPh4]+ and [PPN]+ cation. The obtained compounds have been characterized by single‐crystal X‐ray diffraction, Raman spectroscopy and quantum‐chemical calculations. In addition, the behavior of halide ions in hydrogen fluoride was investigated by using experimental and quantum‐chemical methods in order to gain knowledge on the acidity of hydrogen halides in HF

Friedel-Crafts Type Methylation with Dimethylhalonium Salts

The dimethylchloronium salt [Me2Cl][Al(OTeF5)(4)] is used to methylate electron-deficient aromatic systems in Friedel-Crafts type reactions as shown by the synthesis ofN-methylated cations, such as [MeNC5F5](+), [MeNC5F4I](+), and [MeN3C3F3](+). To gain a better understanding of such fundamental Friedel-Crafts reactions, the role of the dimethylchloronium cation has been evaluated by quantum-chemical calculations

Soluble Fluoridobromates as Well‐Behaved Strong Fluorination Reagents

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

Synthesis, Crystallographic Characterization and Reactivity of a Phosphinine-B(C6F5)3 Lewis Pair

A phosphinine-borane adduct of a Me3Si-functionalized phosphinine and the Lewis acid B(C6F5)3 has been synthesized and characterized crystallographically for the first time. The reaction strongly depends on the nature of the substituents in the α-position of the phosphorus heterocycle. In contrast, the reaction of B2H6 with various substituted phosphinines leads to an equilibrium between the starting materials and the phosphinine–borane adducts that is determined by the Lewis basicity of the phosphinine. The novel phosphinine borane adduct (6-B(C6F5)3) shows rapid and facile insertion and [4+2] cycloaddition reactivity towards phenylacetylene. A hitherto unknown dihydro-1-phosphabarrelene is formed with styrene. The reaction with an ester provides a new, facile and selective route to 1-R-phosphininium salts. These salts then undergo a [4+2] cycloaddition in the presence of Me3Si−C≡CH and styrene to cleanly form unprecedented derivatives of 1-R-phosphabarrelenium salts

Non-classical polyinterhalides of chlorine monofluoride: experimental and theoretical characterization of [F(ClF)3]−

We present the synthesis and characterization of the first non-classical Cl(I) polyinterhalide [NMe4][F(ClF)3] as well as the homologous polychloride [NPr3Me][Cl7]. Both salts were obtained from the reaction of the corresponding ammonium chlorides with ClF or Cl2, respectively. Quantum-chemical investigations predict an unexpected planar structure for the [F(ClF)3]− anion

Preparation and Characterization of [Au(CF3)xF3−x(SIMes)] (x=1–3) Complexes

Trifluoromethylation of [AuF3(SIMes)] with the Ruppert–Prakash reagent TMSCF3 in the presence of CsF yields the product series [Au(CF3)xF3−x(SIMes)] (x=1–3). The degree of trifluoromethylation is solvent dependent and the ratio of the species can be controlled by varying the stoichiometry of the reaction, as evidenced from the 19F NMR spectra of the corresponding reaction mixtures. The molecular structures in the solid state of trans‐[Au(CF3)F2(SIMes)] and [Au(CF3)3(SIMes)] are presented, together with a selective route for the synthesis of the latter complex. Correlation of the calculated SIMes affinity with the carbene carbon chemical shift in the 13C NMR spectrum reveals that trans‐[Au(CF3)F2(SIMes)] and [Au(CF3)3(SIMes)] nicely follow the trend in Lewis acidities of related organo gold(III) complexes. Furthermore, a new correlation between the Au−Ccarbene bond length of the molecular structure in the solid state and the chemical shift of the carbene carbon in the 13C NMR spectrum is presented