Behavior of BrO3F and ClO3F Toward Strong Lewis Acids and the Characterization of [XO2][SbF6] (X = Cl, Br) by Single Crystal X-ray Diffraction, Raman Spectroscopy, and Computational Methods

Photochemistry with Chlorine Trifluoride: Syntheses and Characterization of Difluorooxychloronium(V) Hexafluorido(non)metallates(V), [ClOF2 ][MF6 ] (M=V, Nb, Ta, Ru, Os, Ir, P, Sb)

A photochemical route to salts consisting of difluorooxychloronium(V) cations, [ClOF2 ]+ , and hexafluorido(non)metallate(V) anions, [MF6 ]- (M=V, Nb, Ta, Ru, Os, Ir, P, Sb) is presented. As starting materials, either metals, oxygen and ClF3 or oxides and ClF3 are used. The prepared compounds were characterized by single-crystal X-ray diffraction and Raman spectroscopy. The crystal structures of [ClOF2 ][MF6 ] (M=V, Ru, Os, Ir, P, Sb) are layer structures that are isotypic with the previously reported compound [ClOF2 ][AsF6 ], whereas for M=Nb and Ta, similar crystal structures with a different stacking variant of the layers are observed. Additionally, partial or full O/F disorder within the [ClOF2 ]+ cations of the Nb and Ta compounds occurs. In all compounds reported here, a trigonal pyramidal [ClOF2 ]+ cation with three additional Cl⋅⋅⋅F contacts to neighboring [MF6 ]- anions is observed, resulting in a pseudo-octahedral coordination sphere around the Cl atom. The Cl-F and Cl-O bond lengths of the [ClOF2 ]+ cations seem to correlate with the effective ionic radii of the MV ions. Quantum-chemical, solid-state calculations well reproduce the experimental Raman spectra and show, as do quantum-chemical gas phase calculations, that the secondary Cl⋅⋅⋅F interactions are ionic in nature. However, both solid-state and gas-phase quantum-chemical calculations fail to reproduce the increases in the Cl-O bond lengths with increasing effective ionic radius of M in [MF6 ]- and the Cl-O Raman shifts also do not generally follow this trend.

Reactions of Bromine Fluoride Dioxide, BrO2 F, for the Generation of the Mixed-Valent Bromine Oxygen Cations Br3 O4 + and Br3 O6. Angew Chem Int Ed Engl 2019;58:18928-18930. [PMID: 31622009 PMCID: PMC6973041 DOI: 10.1002/anie.201912271]

A reliable synthesis of unstable and highly reactive BrO₂F is reported. This compound can be converted into BrO₂⁺SbF₆⁻, BrO₂⁺AsF₆⁻_, and BrO₂⁺AsF₆⁻⋅2 BrO₂F. The latter decomposes into mixed‐valent Br₃O₄⋅Br₂⁺AsF₆⁻ with five‐, three‐, one‐, and zero‐valent bromine. BrO₂⁺ H(SO₃CF₃)₂⁻ is formed with HSO₃CF₃. Excess BrO₂F yields mixed‐valent Br₃O₆⁺OSO₃CF₃⁻ with five‐ and three‐valent bromine. Reactions of BrO₂F and MoF₅ in SO₂ClF or CH₂ClF result in Cl₂BrO₆⁺Mo₃O₃F₁₃⁻. The reaction of BrO₂F with (CF₃CO)₂O and NO₂ produces O₂Br‐O‐CO‐CF₃ and the known NO₂⁺Br(ONO₂)₂⁻. All of these compounds are thermodynamically unstable.

Reactive p-block cations stabilized by weakly coordinating anions

The chemistry of the p-block elements is a huge playground for fundamental and applied work. With their bonding from electron deficient to hypercoordinate and formally hypervalent, the p-block elements represent an area to find terra incognita. Often, the formation of cations that contain p-block elements as central ingredient is desired, for example to make a compound more Lewis acidic for an application or simply to prove an idea. This review has collected the reactive p-block cations (rPBC) with a comprehensive focus on those that have been published since the year 2000, but including the milestones and key citations of earlier work. We include an overview on the weakly coordinating anions (WCAs) used to stabilize the rPBC and give an overview to WCA selection, ionization strategies for rPBC-formation and finally list the rPBC ordered in their respective group from 13 to 18. However, typical, often more organic ion classes that constitute for example ionic liquids (imidazolium, ammonium, etc.) were omitted, as were those that do not fulfill the - naturally subjective -"reactive"-criterion of the rPBC. As a rule, we only included rPBC with crystal structure and only rarely refer to important cations published without crystal structure. This collection is intended for those who are simply interested what has been done or what is possible, as well as those who seek advice on preparative issues, up to people having a certain application in mind, where the knowledge on the existence of a rPBC that might play a role as an intermediate or active center may be useful.

A rare example of a krypton difluoride coordination compound: [BrOF2][AsF6] x 2 KrF2

The synthesis of [BrOF(2)][AsF(6)] x 2 KrF(2), its structural characterization, and bonding are described in this study. Although several KrF(2) adducts with transition metal centers have been previously reported, none have been crystallographically characterized. The solid-state Raman spectrum of [BrOF(2)][AsF(6)] x 2 KrF(2) has been assigned with the aid of quantum-chemical calculations. The low-temperature (-173 degrees C) X-ray crystal structure of [BrOF(2)][AsF(6)] x 2 KrF(2) consists of isolated molecular units and represents an example of KrF(2) coordinated to a main-group atom. The coordination geometry around the BrOF(2)(+) cation renders the free valence electron lone pair more compact than in free BrOF(2)(+). The KrF(2) ligands are coordinated trans to the fluorine atoms of BrOF(2)(+) with the AsF(6)(-) anion coordinated trans to oxygen. The quantum theory of atoms in molecules (QTAIM) and electron localization function (ELF) analyses have been carried out in order to define the nature of the bonding in the complex. A significant amount of charge (0.25 e) is transferred to BrOF(2)(+) from the two KrF(2) ligands (0.10 e each) and from the AsF(6)(-) anion (0.05 e). Significant polarization also occurs within the KrF(2) ligands, which enhances the anionic characters of the fluorine bridges. The interaction energy is mostly governed by the electrostatic interaction of the positively charged bromine atom with the surrounding fluorine atoms.

Fluoride ion donor properties of cis-OsO(2)F(4): synthesis, raman spectroscopic study, and X-ray crystal structure of [OsO(2)F(3)][Sb(2)F(11)]

The salt, [OsO(2)F(3)][Sb(2)F(11)], has been synthesized by dissolution of cis-OsO(2)F(4) in liquid SbF(5), followed by removal of excess SbF(5) at 0 degrees C to yield orange, crystalline [OsO(2)F(3)][Sb(2)F(11)]. The X-ray crystal structure (-173 degrees C) consists of an OsO(2)F(3)(+) cation fluorine bridged to an Sb(2)F(11)(-) anion. The light atoms of OsO(2)F(3)(+) and the bridging fluorine atom form a distorted octahedron around osmium in which the osmium atom is displaced from its center toward an oxygen atom and away from the trans-fluorine bridge atom. As in other transition metal dioxofluorides, the oxygen ligands are cis to one another and the fluorine bridge atom is trans to an oxygen ligand and cis to the remaining oxygen ligand. The Raman spectrum (-150 degrees C) of solid [OsO(2)F(3)][Sb(2)F(11)] was assigned on the basis of the ion pair observed in the low-temperature crystal structure. Under dynamic vacuum, [OsO(2)F(3)][Sb(2)F(11)] loses SbF(5), yielding the known [mu-F(OsO(2)F(3))(2)][Sb(2)F(11)] salt with no evidence for [OsO(2)F(3)][SbF(6)] formation. Attempts to synthesize [OsO(2)F(3)][SbF(6)] by the reaction of [OsO(2)F(3)][Sb(2)F(11)] with an equimolar amount of cis-OsO(2)F(4) or by a 1:1 stoichiometric reaction of cis-OsO(2)F(4) with SbF(5) in anhydrous HF yielded only [mu-F(OsO(2)F(3))(2)][Sb(2)F(11)]. Quantum-chemical calculations at the SVWN and B3LYP levels of theory and natural bond orbital analyses were used to calculate the gas-phase geometries, vibrational frequencies, natural population analysis charges, bond orders, and valencies of OsO(2)F(3)(+), [OsO(2)F(3)][Sb(2)F(11)], [OsO(2)F(3)][SbF(6)], and Sb(2)F(11)(-). The relative thermochemical stabilities of [OsO(2)F(3)][SbF(6)], [OsO(2)F(3)][Sb(2)F(11)], [OsO(2)F(3)][AsF(6)], [mu-F(OsO(2)F(3))(2)][SbF(6)], [mu-F(OsO(2)F(3))(2)][Sb(2)F(11)], and [mu-F(OsO(2)F(3))(2)][AsF(6)] were assessed using the appropriate Born-Haber cycles to account for the preference for [mu-F(OsO(2)F(3))(2)][Sb(2)F(11)] formation over [OsO(2)F(3)][SbF(6)] formation and for the inability to synthesize [OsO(2)F(3)][SbF(6)].

Density Functional Study of Structures and Electron Affinities of BrO4F/BrO4F-

The structures, electron affinities and bond dissociation energies of BrO₄F/BrO₄F⁻ species have been investigated with five density functional theory (DFT) methods with DZP++ basis sets. The planar F-Br…O₂…O₂ complexes possess ³A′ electronic state for neutral molecule and ⁴A′ state for the corresponding anion. Three types of the neutral-anion energy separations are the adiabatic electron affinity (EA_ad), the vertical electron affinity (EA_vert), and the vertical detachment energy (VDE). The EA_ad value predicted by B3LYP method is 4.52 eV. The bond dissociation energies D_e (BrO₄F → BrO_4-mF + O_m) (m = 1–4) and D_e⁻ (BrO₄F⁻ → BrO_4-mF⁻ + O_m and BrO₄F⁻ → BrO_4-mF + O_m⁻) are predicted. The adiabatic electron affinities (EA_ad) were predicted to be 4.52 eV for F-Br…O₂…O₂ (³A′←⁴A′) (B3LYP method).