Syntheses and crystal structures of [Mg(HF)2](SbF6)2 and [Ca(HF)2](SbF6)2: new examples of HF acting as a ligand to metal centres

[Mg(HF)₂](SbF₆)₂ and [Ca(HF)₂](SbF₆)₂ monocrystals were grown from the corresponding hexafluoroantimonates(V) dissolved in anhydrous hydrogen fluoride. [Mg(HF)₂](SbF₆)₂ crystallizes in the space group Pnma (no. 62) with a=1249.1(4) pm, b=1230.2(4) pm, c=699.1(2) pm, V=1.0742(6) nm³, Z=4. Magnesium is octahedrally coordinated by six fluorine atoms from which two belong to two HF molecules. The structure can be represented by alternating rows of magnesium and antimony atoms running parallel to the c-axis. Magnesium atoms are connected by cis bridging Sb(2)F₆ units along the a-axis and by trans bridging Sb(1)F₆ units along the b-axis. In this way a three-dimensional network is formed.[Ca(HF)₂](SbF₆)₂ crystallizes in the space group P2₁/n (no. 14) with a=935.2(3) pm, b=1088.7(3) pm, c=1104.8(3) pm, β=106.697(5)°, V=1.0774(5) nm³, Z=4. The coordination sphere around the calcium atom consists of eight fluorine atoms which define the vertices of an Archimedean antiprism. The two HF molecules directly coordinate the calcium atom and their fluorine atoms are placed in the corners of different square faces of the Archimedean antiprism. The Ca-F(HF) distances are shorter than the Ca-F(Sb) distances. The Sb(1)F₆ and Sb(2)F₆ groups have four equatorial bridging fluorine atoms, while the Sb(3)F₆ groups have only two bridging trans F ligands. The Ca atoms in the [−1,0,1] plane are connected by equatorial F ligands of Sb(1)F₆ and Sb(2)F₆ units, forming a [Ca(SbF₆)⁺]_n layer. These layers are connected by trans bridging Sb(3)F₆ groups. HF molecules occupy the space between these layers and additionally contribute to the connection between the layers by hydrogen bonding.     

Laser-excited luminescence and absorption study of mixed valence for K2Pt(CN)4—K2Pt(CN)6 crystals

Crystals of K₂Pt(CN)₆ doped with Pt(CN)^2?₄ show an absorption band at 337 nm which is assigned as a mixed-valence (MV) transition from Pt (II) to Pt(IV). From a Hush model analysis, the absorption band is interpreted to be class II in the Day—Robin scheme. When the MV band is laser excited at 337 nm, emmision is observed from Pt(CN)^2?₄ clusters.     

Blue-shifted hydrogen-bonded complexes. II. CH3F(HF)1 n 3 and CH2F2(HF)1 n 3

The equilibrium structures, binding energies, and vibrational spectra of the clusters CH₃F(HF)_{1 n 3} and CH₂F₂(HF)_{1 n 3} have been investigated with the aid of large-scale ab initio calculations performed at the Møller–Plesset second-order level. In all complexes, a strong C–FH–F halogen–hydrogen bond is formed. For the cases n = 2 and n = 3, blue-shifting C–HF–H hydrogen bonds are formed additionally. Blue shifts are, however, encountered for all C–H stretching vibrations of the fluoromethanes in all complexes, whether they take part in a hydrogen bond or not, in particular also for n = 1. For the case n = 3, blue shifts of the ν(C–H) stretching vibrational modes larger than 50 cm⁻¹ are predicted. As with the previously treated case of CHF₃(HF)_{1 n 3} complexes (A. Karpfen, E. S. Kryachko, J. Phys. Chem. A 107 (2003) 9724), the typical blue-shifting properties are to a large degree determined by the presence of a strong C–FH–F halogen–hydrogen bond. Therefore, the term blue-shifted appears more appropriate for this class of complexes. Stretching the C–F bond of a fluoromethane by forming a halogen–hydrogen bond causes a shortening of all C–H bonds. The shortening of the C–H bonds is proportional to the stretching of the C–F bond.     

Spectroscopic properties of guanidinium zinc sulphate [C(NH2)3]2Zn(SO4)2 and ab initio calculations of [C(NH2)3]2 and HC(NH2)3

Raman and FTIR spectra of guanidinium zinc sulphate [C(NH₂)₃]₂Zn(SO₄)₂ are recorded and the spectral bands assignment is carried out in terms of the fundamental modes of vibration of the guanidinium cations and sulphate anions. The analysis of the spectrum reveals distorted SO₄²⁻ tetrahedra with distinct S–O bonds. The distortion of the sulphate tetrahedra is attributed to Zn–O–S–O–Zn bridging in the structure as well as hydrogen bonding. The CN₃ group is planar which is expressed in the twofold symmetry along the C–N (1) vector. Spectral studies also reveal the presence of hydrogen bonds in the sample. The vibrational frequencies of [C(NH₂)₃]₂ and HC(NH₂)₃ are computed using Gaussian 03 with HF/6-31G* as basis set.     

Photochemistry of (η5)-C5H5)Mn(CO)2[C(C6H5)2]. Generation of the diphenylcarbene radical anion

The electronic absorption spectrum of (η⁵-C₅H₅)Mn(CO)₂[C(C₆H₅)₂]shows an intense maximum which is assigned to a MLCT transition in which the empty p_π orbital on the carbene carbon is populated. Upon irradiation of this band, the complex undergoes a decomposition with a disappearance quantum yield Φ = 0.10 ± 0.01 independent of solvent. In the CT excited state, the complex can be roughly described as containing d⁵ Mn^II and a diphenylcarbene radical anion ligand C(C₆H₅)₂^?. Due to the kinetic lability, the complex decomposes producing a Mn^II species and the free carbene radical anion, which then undergoes secondary reactions. In addition, small amounts of substitution product are observed. It is proposed that prior to total decomposition of the excited state, a radical pair (η⁵-C₅H₅)Mn(CO)₂S⁺/C(C₆H₅)₂^?forms (S = solvent). A back electron transfer from C(C₆H₅)₂^?to the labile cation competes with decomposition to produce the substituted complex and free carbene.     

Chemical HF laser emission from the CHF + O2 reaction

HF laser emission was observed in the flash photolysis (λ ? 165 nm) of mixtures of O₂ and CHFCl₂. A total of 15 transitions ranging from Δυ = 3 → 2 to 1 → o were identified. The laser intensity was found to increase linearly with flash energy. The effects of temperature, reactant concentration and buffer gas pressure have been examined. The stimulated emission is concluded to result primary from the following reactions:

No CO₂ laser emission was detected. A simple gain calculation revealed that only a small fraction of reaction energy (E_int ≈ 180 kcal/mole) was channeled into the HF product. Since the addition of D₂ generated weak DF laser emission (Δυ = 3 → 2 to 1 → o) at only a minor expense (< 10%) to the HF emission, F atoms are believed to be formed as one of the minor decomposition products of FCOOH.     

Silver-silver(I) system in superacid mixtures HF+SbF5

An electrochemical study of silver in superacid medium HF+SbF₅ shows that Ag is not oxidized and that the couple Ag/Ag(I) may be used as a reference electrode in mixtures of HF and SbF₅ containing 30% of SbF₅ (by weight). From potentiometric measurements with a silver electrode, it is shown that AgSbF₆ is slightly soluble and the solubility product is determined (log(K_s/mol²l^?2)=1.1). Evidence for the strong acidity of SbF₅ is demonstrated and it is shown that there are no polymers (such as Sb₂F₁₁^?) in the concentration range 0–3 M of SbF₅.     

Structures, energy bands and conductivities of (Me3NEt)[Pd(dmit) 2]2 and (NEt4)[Pd(dmit) 2]2

The electrical conductive molecular crystals (Me₃NEt)[Pd(dmit) ₂]₂ and (NEt₄)[Pd (dmit) ₂]₂ (dmit = 4,5-dimercapto-1,3-dithiole-2-thione) have been prepared, and their crystal structures and conductivity-temperature curves have been determined. The fact that the conductivity at room temperature of (Me₃NEt)[Pd(dmit) ₂]₂ (σ = 58 Ω^-1 cm^-1) is much higher than that of (Net₄)-[Pd(dmit)₂]₂ (σ = 2.2 Ω^-1.cm^-1) has been rationally explained by the results of energy band calculations. (MeNEt₃)[Pd(dmit)₂]₂ belongs to monoclinic system, P2₁/m space group and (Net₄)[Pd (dmit)₂]₂ belongs to triclinic system, space group. The structural conducting component of the crystals is the planar coordinative anion [Pd(dmit)₂]^0.5- which forms the face-to-face dimmer. [Pd(dmit)₂]^- ₂These dimers have been further constructed to be a kind of two-dimensional (2-D) conductive molecular sheet by means of S_S intermolecular interactions. The tiny difference of the above 2-D molecular sheets of the two title crystals has resulted in one order of magnitude difference of conductivities.     

Structure of two new borates YCa3(AlO)3(BO3)4 and YCa3(GaO)3(BO3)4

By replacing Mn in YCa₃(MnO)₃(BO₃)₄ with trivalent Al and Ga, two new borates with the compositions of YCa₃(MO)₃(BO₃)₄ (M=Al, Ga) were prepared by solid-state reaction. Structure refinements from X-ray powder diffraction data revealed that both of them are isostructural to gaudefroyite with a hexagonal space group P6₃/m. Cell parameters of a=10.38775(13)Å, c=5.69198(10)Å for the Al-containing compound and a=10.5167(3)Å, c=5.8146(2)Å for the Ga analog were obtained from the refinements. The structure is constituted of AlO₆ or GaO₆ octahedral chains interconnected by BO₃ groups in the ab plane to form a Kagomé-type lattice, leaving trigonal and apatite-like tunnels. It is found that most rare-earth and Cr, Mn ions can be substituted into the Y³⁺ and M³⁺ sites, respectively, and the preference of rare-earth ions to locate in the trigonal tunnel is correlated to the sizes of the M³⁺ ions.     

Halofluorination of alkenes with ionic liquid EMIMF(HF)2.3

Halofluorination of alkene by means of N-halosuccinimide and ionic liquid, 1-ethyl-3-methylimidazorium oligo hydrogenfluoride (EMIMF(HF)_2.3), was demonstrated. Various alkenes were converted into β-halo organofluorides in good yields after non-aqueous work-up.     

Fluorination with ionic liquid EMIMF(HF)2.3 as mild HF source

Hydrogen fluoride is a basic fluorinating reagent, but handling it is difficult. For this reason, some modified fluorinating reagents such as HF-pyridine, Et₃N-HF, and poly(hydrogen fluoride) complex have been developed. Those reagents, however, still require aqueous work-up procedures which generate hydrogen fluoride. Recently, ionic liquids have received much attention because of the ease in handling them and the possibility of non-aqueous work-up. An ionic liquid, 3-ethyl-1-methyimidazolium oligo hydrogen fluoride (EMIMF(HF)_2.3), which is stable in air and moisture, can be used as a hydrogen fluoride equivalent for some fluorination reactions; it does not require an aqueous work-up.     

Spin transition in [Fe(phen)2(NCS)2] and [Fe(bipy)2(NCS)2]: Hysteresis and effect of crystal quality

Detailed magnetic susceptibility measurements on the polycrystalline complexes [Fe(phen)₂(NCS)₂] (phen = 1.10-phenanthroline) and [Fe(bipy)₂(NCS)₂] (bipy = 2,2′-bipyridine) have revealed a narrow hysteresis in both systems indicative of a first-order nature of the spin transition ⁵T_2g(O_h) ? ¹ A_tg(O_h). The crystal quality, in particular crystal defects (through preparation or grinding), have been shown to influence strongly the spin transition behaviour.     

Structure and properties of double complex salts [Co(NH3)6][Fe(CN)6] and [Co(NH3)6]2[Cu(C2O4)2]3

Double complex salts (DCSs) [Co(NH₃)₆][Fe(CN)₆] (I) and [Co(NH₃)₆]₂[Cu(C₂O₄)₂]₃ (II) and complex [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O (III) are synthesized and investigated by single crystal XRD, crystal optics, and elemental analysis. The crystalline phases of I, II, and III (R-3, P2₁/c, and Pnnm space groups respectively) have the following crystallographic characteristics: a = 10.9804(2) ?, b = 10.9804(2) ?, c = 10.8224(3) ?, V = 1130.03(4) ?³, Z = 3, d _x = 1.65 g/cm³ (I); a = 9.6370(2) ?, b = 10.2452(2) ?, c = 13.2108(3) ?, V = 1932.90(9) ?³, Z = 2, d _x= 1.97 g/cm³ (II), and a = 11.7658(3) ?, b = 11.7254(3) ?, c = 14.1913(4) ?, V = 1304.34(5) ?³, Z = 2, d _x = 1.68 g/cm³ (III). This paper investigates the products of DCS thermolysis in a hydrogen atmosphere: the intermetallic compound CoFe with the bcc parameter a = 2.852 ? for I and a heterogeneous mixture of Co and Cu in the decomposition of II. The coordinated CN⁻ and C₂O₄²⁻ groups then turn into NH₃, hydrocarbons, and CO₂. The dominant hydrocarbon is methane.     

Collisional relaxation Of HF(v = 3,4) By HF,CH4 and CD4

Direct excitation of overtone vibrations in combination with near-infrared fluorescence detection provides collisional relaxation rate constants for HF(v = 3,4) by HF, CH₄ and CD₄. Observing fluorescence from a few rotational levels shows that the rotational manifold in HF(v = 4) equilibrates in about half the gas kinetic collision time.     

Novel ammonium hexafluoroarsenate salts from reaction of (CF3)2NH,CF3N(OCF3)H,CF3N[OCF(CF3)2]H,CF3NHF and SF5NHF with the strong acid HF/ASF5.

Reactions of the fluorinated amines (CF₃)₂NH, CF₃N(OCF₃)H, CF₃N[OCF(CF₃)₂]H, CF₃NHF and SF₅NHF with the strong acid HF/AsF₅ form the corresponding ammonium salts R_f¹R_f²NH₂⁺AsF₆^? and R_fNFH₂⁺ AsF₆^? in high yield. [R_f¹=CF₃, R_f²=CF₃, CF₃O, (CF₃)₂CFO; R_f=CF₃, SF₅] The colorless crystalline solids are stable for prolonged periods at 22°C in sealed FEP containers. They have dissociation pressures at 22°C ranging from ～5 torr (R_fNFH₂⁺ AsF₆^?) to ～50 torr [CF₃N(OCF₃)H₂⁺AsF₆^?]. ¹⁹F NMR and Raman spectroscopy were used to identify the compounds.     

Vibrational spectroscopic study of the arsenate mineral strashimirite Cu8(AsO4)4(OH)4·5H2O—Relationship to other basic copper arsenates

The basic copper arsenate mineral strashimirite Cu₈(AsO₄)₄(OH)₄·5H₂O from two different localities has been studied by Raman spectroscopy and complemented by infrared spectroscopy. Two strashimirite mineral samples were obtained from the Czech (sample A) and Slovak (sample B) Republics. Two Raman bands for sample A are identified at 839 and 856 cm⁻¹ and for sample B at 843 and 891 cm⁻¹ are assigned to the ν₁ (AsO₄³⁻) symmetric and the ν₃ (AsO₄³⁻) antisymmetric stretching modes, respectively. The broad band for sample A centred upon 500 cm⁻¹, resolved into component bands at 467, 497, 526 and 554 cm⁻¹ and for sample B at 507 and 560 cm⁻¹ include bands which are attributable to the ν₄ (AsO₄³⁻) bending mode. In the Raman spectra, two bands (sample A) at 337 and 393 cm⁻¹ and at 343 and 374 cm⁻¹ for sample B are attributed to the ν₂ (AsO₄³⁻) bending mode. The Raman spectrum of strashimirite sample A shows three resolved bands at 3450, 3488 and 3585 cm⁻¹. The first two bands are attributed to water stretching vibrations whereas the band at 3585 cm⁻¹ to OH stretching vibrations of the hydroxyl units. Two bands (3497 and 3444 cm⁻¹) are observed in the Raman spectrum of B. A comparison is made of the Raman spectrum of strashimirite with the Raman spectra of other selected basic copper arsenates including olivenite, cornwallite, cornubite and clinoclase.     

Antimonypentafluoroorthotellurates: Sb(OTeF5)3, Sb(OTeF5)5 and salts of Sb(OTeF5)6−

Antimony(III)pentafluoroorthotellurate has been synthesized from SbF₃ and B(OTeF₅)₃. Contrary to a previous report it is a low melting, sublimable solid (mp = 28°, bp (0.1 torr) = 68°, ¹⁹F - NMR: AB₄ spinsystem δ (A) = ?42.7, δ (B) = ?38.1, J (AB) = 186 Hz). It reacts with F₂, Cl₂ and Br₂ to give SbF₂(OTeF₅)₃, SbCl₄⁺Sb(OTeF₅)₆^? and SbBr₄⁺ Sb(OTeF₅)₆^? respectively. Interaction of Xe(OTeF₅)₂ and Sb(OTeF₅)₃ yields Sb(OTeF₅)₅, which is unstable at room temperature. Salts containing the new anion Sb(OTeF₅)₆^? have been synthesized either from Sb(OTeF₅)₅ and a corresponding pentafluoroorthotellurate e.g. Sb(OTeF₅)₅ + NMe₄⁺ OTeF₅^? = NMe₄⁺ Sb(OTeF₅)₆^?, or from SbCl₄ Sb(OTeF₅)₆^? and an appropriate chloride SbCl₄⁺ Sb(OTeF₅)₆^? + NOCl = SbCl₅ + NO⁺ Sb(OTeF₅)₆^?, or oxidatively, using a mixture of Xe(OTeF₅)₂ and Sb(OTeF₅)₅, e.g. C₆F₆ + $\text{1}\text{2}$ Xe(OTeF₅)₂ + Sb(OTeF₅)₅ = C₆F₆⁺ Sb(OTeF₅)₆^? + $\text{1}\text{2}$ Xe.     

Crystal structure and single crystal EPR of (NH4)2(15-crown-5)3[Cu(mnt)2] and (NH4)2(benzo-15-crown-5)4[Cu(mnt)2]·0.5H2O

The X-ray crystal structures of (NH4)2(15-crown-5)3[Cu(mnt)2] (1) and (NH4)2(benzo-15-crown-5)4- [Cu(mnt)2]·0.5H2O (2) were determined. Two single crystals are composed of distinct structures of ammonium-crown ether supramolecular cation and [Cu(mnt)2]2- anion. The triple-decker dication in complex 1 and a sandwich dimmer in complex 2 were observed. X-Band EPR studies on the single crystals of both complex 1 and complex 2 have been carried out at room temperature, which revealed that complex 2 showed a perfect hyperfine structure of Cu whereas that of complex 1 could not be observed. The principal values and direction cosines of the principal axes of the g and A tensors were computed by a least-squares fitting procedure. The spin density of Cu(Ⅱ) was estimated according to the principal values of the A tensors and compared well with the results calculated based on DFT method.     

One-dimensional chains in uranyl tungstates: Syntheses and structures of A8[(UO2)4(WO4)4(WO5)2] (A=Rb, Cs) and Rb6[(UO2)2O(WO4)4]

Three new uranyl tungstates, A₈[(UO₂)₄(WO₄)₄(WO₅)₂] (A=Rb (1), Cs (2)), and Rb₆[(UO₂)₂O(WO₄)₄] (3), were prepared by high-temperature solid-state reactions and their structures were solved by direct methods on twinned crystals, refined to R₁=0.050, 0.042, and 0.052 for 1, 2, and 3, respectively. Compounds 1 and 2 are isostructural, monoclinic P2₁/n, (1): a=11.100(7), b=13.161(9), , β=90.033(13)°, , Z=8 and (2): , , , β=89.988(2)°, , Z=8. There are four symmetrically independent U⁶⁺ sites that form linear uranyl [O=U=O]²⁺ cations with rather distorted coordination in their equatorial planes. There are six W positions: W(1) and W(2) have square-pyramidal coordination (WO₅), whereas W(3), W(4), W(5), and W(6) are tetrahedrally coordinated. The structures are based upon a novel type of one-dimensional (1D) [(UO₂)₄(WO₄)₄(WO₅)₂]⁴⁻ chains, consisting of WU₄O₂₅ pentamers linked by WO₄ tetrahedra and WO₅ square pyramids. The chains run parallel to the a-axis and are arranged in modulated pseudo-2D-layers parallel to (0 1 0). The A⁺ cations are in the interlayer space between adjacent pseudo-layers and provide a 3D integrity of the structures. Compounds 1 and 2 are the first uranyl tungstates with 2/3 of W atoms in tetrahedral coordination. Such a high concentration of low-coordinated W⁶⁺ cations is probably responsible for the 1D character of the uranyl tungstate units. The compound 3 is triclinic, P1¯ a=10.188(2), b=13.110(2), , α=97.853(3), β=96.573(3), γ=103.894(3)°, , Z=4. There are four U positions in the structure with a typical coordination of a pentagonal bipyramid that contain uranyl ions, UO₂²⁺, as apical axes. Among eight W sites, the W(1), W(2), W(3), W(4), W(5), and W(6) atoms are tetrahedrally coordinated, whereas the W(7) and W(8) cations have distorted fivefold coordination. The structure contains chains of composition [(UO₂)₂O(WO₄)₄]⁶⁻ composed of UO₇ pentagonal bipyramids and W polyhedra. The chains involve dimers of UO₇ pentagonal bipyramids that share common O atoms. The dimers are linked into chains by sharing corners with WO₄ tetrahedra. The chains are parallel to [−101] and are arranged in layers that are parallel to (1 1 1). The Rb⁺ cations provide linkage of the chains into a 3D structure. The compound 1 has many structural and chemical similarities to its molybdate analog, Rb₆[(UO₂)₂O(MoO₄)₄]. However, the compounds are not isostructural. Due to the tendency of the W⁶⁺ cations to have higher-than-fourfold coordination, part of the W sites adopt distorted fivefold coordination, whereas all Mo atoms in the Mo compound are tetrahedrally coordinated. Distribution of the WO₅ configurations along the chain extension does not conform to its ‘typical’ periodicity. As a result, both the chain identity period and the unit-cell volume are doubled in comparison to the Mo analog, which leads to a new structure type.     

[Gd2(Gly)6(H2O)4](ClO4)6(H2O)5的合成、晶体结构与热化学研究

利用微波技术合成了配合物[Gd₂(Gly)₆(H₂O)₄](ClO₄)₆(H₂O)₅, 进行了化学成分分析、红外表征和热重分析. 应用X衍射仪测定其晶体结构, 该晶体为一维链结构, 属三斜晶系, P 空间群, 晶胞参数: a＝1.1569(17) nm, b＝1.4138(2) nm, c＝1.5642(2) nm, α＝96.910(2)°, β＝102.735(2)°, γ＝105.512(2)°, V＝2.3606(6) nm³, Z＝2, D_c＝2.144 g•cm^－3. 采用精密溶解-反应量热计, 通过设计热化学循环, 计算出了该配合物的标准摩尔生成焓为 －(7960.73±3.23) kJ•mol^－1.