Synthesis and Lewis Acid Properties of (ReO3F)∞ and the X-ray Crystal Structures of (HF)2ReO3F·HF and [N(CH3)4]2-[{ReO3(μ-F)}3(μ3-O)]·CH3CN

Syntheses, Structures, and Bonding of NgF2 ⋅CrOF4 , NgF2 ⋅2CrOF4 (Ng=Kr, Xe), and (CrOF4 )∞

The noble-gas difluoride adducts, NgF₂ ⋅CrOF₄ and NgF₂ ⋅2CrOF₄ (Ng=Kr and Xe), have been synthesized and structurally characterized at low temperatures by Raman spectroscopy and single-crystal X-ray diffraction. The low fluoride ion affinity of CrOF₄ renders it incapable of inducing fluoride ion transfer from NgF₂ (Ng=Kr and Xe) to form ion-paired salts of the [NgF]⁺ cations having either the [CrOF₅ ]^- or [Cr₂ O₂ F₉ ]^- anions. The crystal structures show the NgF₂ ⋅CrOF₄ adducts are comprised of F_t -Ng-F_b - - -Cr(O)F₄ structural units in which NgF₂ is weakly coordinated to CrOF₄ by means of a fluorine bridge, F_b , in which Ng-F_b is elongated relative to the terminal Ng-F_t bond. In contrast with XeF₂ ⋅2MOF₄ (M=Mo or W) and KrF₂ ⋅2MoOF₄ , in which the Lewis acidic, F₄ (O)M- - -F_b - - -M(O)F₃ moiety coordinates to Ng through a single M- - -F_b -Ng bridge, both fluorine ligands of NgF₂ coordinate to CrOF₄ molecules to form F₄ (O)Cr- - -F_b -Ng-F_b - - -Cr(O)F₄ adducts in which both Ng-F_b bonds are only marginally elongated relative to the Ng-F bonds of free NgF₂ . Quantum-chemical calculations show that the Cr-F_b bonds of NgF₂ ⋅CrOF₄ and NgF₂ ⋅2CrOF₄ are predominantly electrostatic with a small degree of covalent character that accounts for their nonlinear Cr- - -F_b -Ng bridge angles and staggered O-Cr- - -F_b -Ng-F_t dihedral angles. The crystal structures and Raman spectra of two CrOF₄ polymorphs have also been obtained. Both are comprised of fluorine-bridged chains that are cis- and trans-fluorine-bridged with respect to oxygen.

Br2F7− and Br3F10−: peculiar anions showing μ2- and μ3-bridging F-atoms

RbCl and CsCl react with BrF₃ yielding the corresponding decafluoridotribromates(iii), MBr₃F₁₀ (M = Rb, Cs), which were structurally characterized for the first time.

Pentafluoro-oxotellurate(VI) anions of mercury(II); syntheses and structures of [Hg(OTeF5)4](2-), [Hg(OTeF5)5](3-), [Hg2(OTeF5)6](2-), [Hg(OTeF5)4](2-)·Hg(OTeF5)2, and [Hg2(OTeF5)7](3-)·Hg(OTeF5)2

Mercury(II) anions derived from the F5TeO- (teflate) group were synthesized and structurally characterized. The salts, [N(CH2CH3)4]2[Hg(OTeF5)4], [N(CH3)4]3[Hg(OTeF5)5], [N(CH2CH3)4]3[Hg(OTeF5)5], [N(CH3)4]2[Hg2(OTeF5)6], Cs2[Hg(OTeF5)4]·Hg(OTeF5)2, and {Cs3[Hg2(OTeF5)7]·Hg(OTeF5)2}·4SO2ClF, were obtained by reaction of Hg(OTeF5)2 with [M][OTeF5] (M = [N(CH3)4](+), [N(CH2CH3)4](+), Cs(+)) and were characterized by low-temperature single-crystal X-ray diffraction and low-temperature Raman spectroscopy. Unlike in the extensively fluorine-bridged solid-state structures of [HgF3](-) and [HgF4](2-), the less basic and more sterically demanding teflate ligands of the Hg(II) anions show less tendency to bridge. The anions exhibit a variety of structural motifs, ranging from well-isolated tetrahedral [Hg(OTeF5)4](2-) and square-pyramidal [Hg(OTeF5)5](3-) to the chain structures, [Hg2(OTeF5)6](2-) and [Hg2(OTeF5)7](3-)·Hg(OTeF5)2. The geometrical parameters and vibrational frequencies of [Hg(OTeF5)4](2-) (S4), [Hg(OTeF5)5](3-) (C1), and [Hg2(OTeF5)6](2-) (D2) anions, as well as the hypothetical [Hg3(OTeF5)8](2-) (C1) anion, were calculated using density functional theory methods (PBE1PBE/def2-TZVPP), which aided in the assignment of the Raman spectra of [Hg(OTeF5)4](2-), [Hg(OTeF5)5](3-), [Hg2(OTeF5)6](2-), and Cs2[Hg(OTeF5)4]·Hg(OTeF5)2. The calculated geometries were used to assess the effects of solid-state interionic interactions on the anion geometries. For the most part, the gross gas-phase trigonal bipyramidal (tbp) geometry of [Hg(OTeF5)5](3-) adheres to the predicted VSEPR geometry but contrasts with the solid-state anion structures, which have square-pyramidal geometries or geometries that lie between square pyramidal- and tbp-geometries. However, the bond length order calculated for the Hg-O bonds of tbp-[Hg(OTeF5)5](3-), Hg-Oeq > Hg-Oax, is opposite to that predicted by the VSEPR model of molecular geometry. Natural bond orbital analyses provided the associated Mayer bond orders, Mayer valencies, and natural population analysis charges.