Polyanion Condensation in Inorganic and Hybrid Fluoridometallates (IV) of Octahedrally Coordinated Ti, Zr, Hf, V, Cr, W, Mn, Ge, Sn, and Pb.

In fluorides, the M4+ cations of M = Ti, V, Cr, Mn, Ge, Sn, and Pb favour the octahedral coordination of six F ligands. Some examples of M4+ with larger cations (M = Zr, Hf, W) in octahedral coordination are also known. If not enough F ligands are available to have isolated MIVF6 octahedra, they must share their F ligands. The crystal structures of such fluoride metalates (IV) show the variety of possible structural motifs of the zero-dimensional oligomeric anions [M2F11]3- (M = Ti, Cr), [M3F15]3- (M = Zr, Hf), [M3F16]4- (M = Ge), [M4F18]2- (M = Ti, W), [M4F19]3- (M = Ti), [M4F20]4- (M = Ti), [M5F23]3- (M = Ti), [M6F27]3- (M = Ti), [M6F28]4- (M = Ti), [M8F36]4- (M = Ti, Mn), [M10F45]5- (M = Ti) to one-dimensional chains ([MF5]-)∞ (M = V, Ti, Cr, Ge, Sn, Pb), double chains ([M2F9]-)∞ (M = Ti, Mn), columns ([M3F13]-)∞ (M = Ti), ([M4F19]3-)∞ (M = Ti), ([M7F30]2-)∞ (M = Ti), ([M9F38]2-)∞) (M = Ti), two-dimensional layers ([M2F9]-)∞ (M = Cr), ([M8F33]-)∞ (M = Ti), and three-dimensional ([M6F27]3-)∞ (M = Ti) architectures. A discrete monomeric [M2F9]- anion with two MIVF6 octahedra sharing a common face has not yet been experimentally demonstrated, while two examples containing discrete dimeric [M2F10]2- anions (M = Ti) with two MIVF6 octahedra sharing an edge are still in question.

A Unique Two-Dimensional Silver(II) Antiferromagnet Cu[Ag(SO4 )2 ] and Perspectives for Its Further Modifications.

Copper(II) silver(II) sulfate crystallizes in a monoclinic CuSO4 -related structure with P21 /n symmetry. This quasi-ternary compound features Ag(SO4 )2 2- layers, while the remaining cationic sites may be occupied either completely or partially by Cu2+ cations, corresponding to the formula of (Cux Ag1-x )[Ag(SO4 )2 ], x=0.6-1.0. CuAg(SO4 )2 is antiferromagnetic with large negative Curie-Weiss temperature of -140 K and shows characteristic ordering phenomenon at 40.4 K. Density functional theory calculations reveal that the strongest superexchange interaction is a two-dimensional antiferromagnetic coupling within Ag(SO4 )2 2- layers, with the superexchange constant J2D of -11.1 meV. This renders CuAg(SO4 )2 the rare representative of layered Ag2+ -based antiferromagnets. Magnetic coupling is facilitated by the strong mixing of Ag d(x2 -y2 ) and O 2p states. Calculations show that M2+ sites in MAg(SO4 )2 can be occupied with other similar cations such as Zn2+ , Cd2+ , Ni2+ , Co2+ , and Mg2+ .

Crystal Structures of Xenon(VI) Salts: XeF5Ni(AsF6)3, XeF5AF6 (A = Nb, Ta, Ru, Rh, Ir, Pt, Au), and XeF5A2F11 (A = Nb, Ta).

Experiments on the preparation of the new mixed cations XeF5M(AF6)3 (M = Cu, Ni; A = Cr, Nb, Ta, Ru, Rh, Re, Os, Ir, Pt, Au, As), XeF5M(SbF6)3 (M = Sn, Pb), and XeF5M(BF4)x(SbF6)3-x (x = 1, 2, 3; M = Co, Mn, Ni, Zn) salts were successful only in the preparation of XeF5Ni(AsF6)3. In other cases, mixtures of different products, mostly XeF5AF6 and XeF5A2F11 salts, were obtained. The crystal structures of XeF5Ni(AsF6)3, XeF5TaF6, XeF5RhF6, XeF5IrF6, XeF5Nb2F11, XeF5Ta2F11, and [Ni(XeF2)2](IrF6)2 were determined for the first time on single crystals at 150 K by X-ray diffraction. The crystal structures of XeF5NbF6, XeF5PtF6, XeF5RuF6, XeF5AuF6, and (Xe2F11)2(NiF6) were redetermined by the same method at 150 K. The crystal structure of XeF5RhF6 represents a new structural type in the family of XeF5AF6 salts, which crystallize in four different structural types. The XeF5A2F11 salts (M = Nb, Ta) are not isotypic and both represent a new structure type. They consist of [XeF5]+ cations and dimeric [A2F11]- anions. The crystal structure of [Ni(XeF2)2](IrF6)2 is a first example of a coordination compound in which XeF2 is coordinated to the Ni2+ cation.

Crystal Growth from Anhydrous HF Solutions of M2+ (M = Ca, Sr, Ba) and [AuF6]-, Not Only Simple M(AuF6)2 Salts.

Crystal growth from anhydrous HF solutions of M2+ (M = Ca, Sr, Ba) and [AuF6]- (molar ratio 1:2) gave [Ca(HF)2](AuF6)2, [Sr(HF)](AuF6)2, and Ba[Ba(HF)]6(AuF6)14. [Ca(HF)2](AuF6)2 exhibits a layered structure in which [Ca(HF)2]2+ cations are connected by AuF6 units, while the crystal structure of Ba[Ba(HF)]6(AuF6)14 exhibits a complex three-dimensional (3-D) network consisting of Ba2+ and [Ba(HF)2]2+ cations bridged by AuF6 groups. These results indicate that the previously reported M(AuF6)2 (M = Ca, Sr, Ba) compounds, prepared in the anhydrous HF, do not in fact correspond to this chemical formula. When the initial M2+/[AuF6]- ratio was 1:1, single crystals of [M(HF)](H3F4)(AuF6) were grown for M = Sr. The crystal structure consists of a 3-D framework formed by [Sr(HF)]2+ cations associated with [AuF6]- and [H3F4]- anions. The latter exhibits a Z-shaped conformation, which has not been observed before. Single crystals of M(BF4)(AuF6) (M = Sr, Ba) were grown when a small amount of BF3 was present during crystallization. Sr(BF4)(AuF6) crystallizes in two modifications. A high-temperature α-phase (293 K) crystallized in an orthorhombic unit cell, and a low-temperature ß-phase (150 K) crystallized in a monoclinic unit cell. For Ba(BF4)(AuF6), only an orthorhombic modification was observed in the range 80-230 K. An attempt to grow crystals of Ca(BF4)(AuF6) failed. Instead, crystals of [Ca(HF)](BF4)2 were grown and the crystal structure was determined. During prolonged crystallization of [AuF]6- salts, moisture can penetrate through the walls of the crystallization vessel. This can lead to partial reduction of Au(V) to A(III) and the formation of [AuF4]- byproducts, as shown by the single-crystal growth of [Ba(HF)]4(AuF4)(AuF6)7. Its crystal structure consists of [Ba(HF)]2+ cations connected by AuF6 octahedra and square-planar AuF4 units. The crystal structure of the minor product [O2]2[Sr(HF)]5[AuF6]12·HF was also determined.

Silver route to cuprate analogs.

The parent compound of high-[Formula: see text] superconducting cuprates is a unique Mott insulator consisting of layers of spin-[Formula: see text] ions forming a square lattice and with a record high in-plane antiferromagnetic coupling. Compounds with similar characteristics have long been searched for without success. Here, we use a combination of experimental and theoretical tools to show that commercial [Formula: see text] is an excellent cuprate analog with remarkably similar electronic parameters to [Formula: see text] but larger buckling of planes. Two-magnon Raman scattering and inelastic neutron scattering reveal a superexchange constant reaching 70% of that of a typical cuprate. We argue that structures that reduce or eliminate the buckling of the [Formula: see text] planes could have an antiferromagnetic coupling that matches or surpasses the cuprates.

Syntheses of Dioxygenyl Salts by Photochemical Reactions in Liquid Anhydrous Hydrogen Fluoride: X-ray Crystal Structures of α- and ß-O2Sn2F9, O2Sn2F9·0.9HF, O2GeF5·HF, and O2[Hg(HF)]4(SbF6)9.

By treating gaseous, liquid, or solid fluorides with UV-photolyzed O2/F2 mixtures and by treating solid oxides with UV-photolyzed F2 (or O2/F2 mixtures) in liquid anhydrous HF at ambient temperature, we investigated the possibility of the preparation of O2MIIIF4 (M = B, Fe, Co, Ag), O2MIVF5 (M = Ti, Sn, Pb), (O2)2MIVF6 (M = Ti, Ge, Sn, Pb, Pd, Ni, Mn), O2MIV2F9 (M = Sn), O2MVF6 (M = As, Sb, Au, Pt), O2MV2F11 (M = Pt), O2MVIF7 (M = Se), (O2)2MVIF8 (M = Mo, W), and O2MVIIF8 (M = I). The approach has been successful in the case of previously known O2BF4, O2MF6 (M = As, Sb, Au; Pt), O2GeF5, and (O2)2(Ti7F30). Novel compounds O2GeF5·HF, α-O2Sn2F9 (1-D), and the HF-solvated and nonsolvated forms of ß-O2Sn2F9 (2-D) were synthesized and their crystal structures determined using single-crystal X-ray diffraction. The crystal structures of all of these materials arise from the condensation of octahedral MF6 (M = Ge, Sn) units. The anion in the crystal structure of O2GeF5·HF is comprised of infinite ([GeF5]-)∞ chains of GeF6 octahedra that share common vertices. The HF molecules and O2+ cations are located between the chains. The crystal structure of α-O2SnF9 (1-D) is constructed from [O2]+ cations and polymeric ([Sn2F9]-)∞ anions which appear as two parallel infinite chains comprised of SnF6 units, where each SnF6 unit of one chain is connected to a SnF6 unit of the second chain through a shared fluorine vertex. The single-crystal structure determination of [O2][Sn2F9]·0.9HF reveals that it is comprised of two-dimensional ([Sn2F9]-)∞ grids with [O2]+ cations and HF molecules located between them. The 2-D grids have a wavelike conformation. The ([Sn2F9]-)∞ layer contains both six- and seven-coordinated Sn(IV) atoms that are interconnected by bridging fluorine atoms. A new, more complex [O2]+ salt, O2[Hg(HF)]4[SbF6]9, was prepared. In its crystal structure, the Hg atoms bridge to SbF6 units to form a 3-D framework. The O2+ cations are located inside the voids while the HF molecules are bound to Hg atoms through the F atom. Attempts to prepare several chlorine analogues of O2+ fluorine salts (i.e., O2TiCl5 and O2MCl6 (M = Nb, Sb)) failed.

Noble-Gas Chemistry More than Half a Century after the First Report of the Noble-Gas Compound.

Recent development in the synthesis and characterization of noble-gas compounds is reviewed, i.e., noble-gas chemistry reported in the last five years with emphasis on the publications issued after 2017. XeF2 is commercially available and has a wider practical application both in the laboratory use and in the industry. As a ligand it can coordinate to metal centers resulting in [M(XeF2)x]n+ salts. With strong Lewis acids, XeF2 acts as a fluoride ion donor forming [XeF]+ or [Xe2F3]+ salts. Latest examples are [Xe2F3][RuF6]·XeF2, [Xe2F3][RuF6] and [Xe2F3][IrF6]. Adducts NgF2·CrOF4 and NgF2·2CrOF4 (Ng = Xe, Kr) were synthesized and structurally characterized at low temperatures. The geometry of XeF6 was studied in solid argon and neon matrices. Xenon hexafluoride is a well-known fluoride ion donor forming various [XeF5]+ and [Xe2F11]+ salts. A large number of crystal structures of previously known or new [XeF5]+ and [Xe2F11]+ salts were reported, i.e., [Xe2F11][SbF6], [XeF5][SbF6], [XeF5][Sb2F11], [XeF5][BF4], [XeF5][TiF5], [XeF5]5[Ti10F45], [XeF5][Ti3F13], [XeF5]2[MnF6], [XeF5][MnF5], [XeF5]4[Mn8F36], [Xe2F11]2[SnF6], [Xe2F11]2[PbF6], [XeF5]4[Sn5F24], [XeF5][Xe2F11][CrVOF5]·2CrVIOF4, [XeF5]2[CrIVF6]·2CrVIOF4, [Xe2F11]2[CrIVF6], [XeF5]2[CrV2O2F8], [XeF5]2[CrV2O2F8]·2HF, [XeF5]2[CrV2O2F8]·2XeOF4, A[XeF5][SbF6]2 (A = Rb, Cs), Cs[XeF5][BixSb1-xF6]2 (x = ~0.37-0.39), NO2XeF5(SbF6)2, XeF5M(SbF6)3 (M = Ni, Mg, Zn, Co, Cu, Mn and Pd) and (XeF5)3[Hg(HF)]2(SbF6)7. Despite its extreme sensitivity, many new XeO3 adducts were synthesized, i.e., the 15-crown adduct of XeO3, adducts of XeO3 with triphenylphosphine oxide, dimethylsulfoxide and pyridine-N-oxide, and adducts between XeO3 and N-bases (pyridine and 4-dimethylaminopyridine). [Hg(KrF2)8][AsF6]2·2HF is a new example of a compound in which KrF2 serves as a ligand. Numerous new charged species of noble gases were reported (ArCH2+, ArOH+, [ArB3O4]+, [ArB3O5]+, [ArB4O6]+, [ArB5O7]+, [B12(CN)11Ne]-). Molecular ion HeH+ was finally detected in interstellar space. The discoveries of Na2He and ArNi at high pressure were reported. Bonding motifs in noble-gas compounds are briefly commented on in the last paragraph of this review.

Preparative Electrosynthesis of Strong Oxidizers at Boron-Doped Diamond Electrode in Anhydrous HF.

The use of the boron-doped diamond electrode as a sufficiently stable electrode for electrochemical measurements/synthesis in liquid anhydrous hydrogen fluoride medium is reported. Electrooxidation of silver(I) has been studied in this solvent by using classical transient electrochemical methods and impedance spectroscopy. It has been found that faradaic currents related to silver(I) oxidation and the fluorine evolution reaction are reasonably separated at the potential scale, which allows efficient electrosynthesis of AgII F2 , a powerful oxidizer. Impedance spectroscopy measurements provide insight into complex mechanism of AgF2 formation. The procedure for electrosynthesis is provided for the first time in both galvanostatic and potentiostatic condition.

Increasing Structural Dimensionality of Alkali Metal Fluoridotitanates(IV).

Reactions between AF (A = Li, Na, K, Rb, Cs) and TiF4 (with starting n(AF):n(TiF4) molar ratios in the range from 3:1 to 1:3) in anhydrous hydrogen fluoride yield [TiF6]2-, [TiF5]-, [Ti4F19]3-, [Ti2F9]-, and [Ti6F27]3- salts. With the exception of the A2TiF6 compounds, which consist of A+ cations and octahedral [TiF6]2- anions, all of these materials arise from the condensation of TiF6 units. The anionic part in the crystal structures of A[TiF5] (A = K, Cs) and A[TiF5]·HF (A = Na, K, Rb) is composed of infinite ([TiF5]-)∞ chains built of TiF6 octahedra sharing joint vertices. Each structure shows a slightly different geometry of the ([TiF5]-)∞ chains. The crystal structure of Na[Ti2F9]·HF is constructed from polymeric ([Ti2F9]-)∞ anions that appear as two parallel infinite zigzag chains comprising TiF6 units, where each TiF6 unit of one chain is connected to a TiF6 unit of the other chain through a shared fluorine vertex. Slow decomposition of single crystals of K4[Ti8F36]·8HF and Rb4[Ti8F36]·6HF ( Shlyapnikov , I. M. ; et al. Chem. Commun. 2013 , 49 , 2703 ) leads to the formation of [Ti2F9]- (Rb) and [Ti6F27]3- (K, Rb) salts. The former displays the same ([Ti2F9]-)∞ double chain as in Na[Ti2F9]·HF, while the anionic part in the latter, ([Ti6F27]3-)∞, represents the first example of a three-dimensional network built of TiF6 octahedra. The ([Ti6F27]3-)∞ anion was also found in [H3O]3[Ti6F27]. The crystal structure determination of Cs3[Ti4F19] revealed a new type of polymeric fluoridotitanate(IV) anion, ([Ti4F19]3-)∞. Similar to the ([Ti2F9]-)∞ anion, it is also built of zigzag double chains comprising TiF6 units. However, in the former there are fewer connections between TiF6 units of two neighboring chains than in the latter.

[Ag(OH2 )2 ][Ag(SO4 )2 ]: A Hydrate of a Silver(II) Salt.

When exposed to air at ambient conditions, AgSO4 slowly reacts with moisture, yielding AgSO4 ⋅H2 O. The crystal structure determination (powder data) shows that it may be described as [Ag(OH2 )2 ][Ag(SO4 )2 ], with some sulfate groups being shared between different Ag2+ cations, resembling in that way its Cu2+ analogue. [Ag(OH2 )2 ][Ag(SO4 )2 ], the first hydrate of a compound of Ag2+ , was extensively characterized using many physicochemical methods.

Canted Antiferromagnetism in Two-Dimensional Silver(II) Bis[pentafluoridooxidotungstate(VI)].

By slow reaction between colorless AgIW2O2F9 and elemental F2 in liquid anhydrous HF, violet platelike single crystals of Ag(WOF5)2 were grown. The crystal structure of Ag(WOF5)2 consists of layers built from Ag2+ cations bridged by [WOF5]- anions and not, as previously assumed, from infinite [AgII-F]+∞ chains and [W2O2F9]- anions. A majority (97%) of the disordered AgII cations are found with square-planar coordination of F/O ligands within the same layer, and they form additional long contacts with O/F atoms originating from the neighboring layers. The remaining 3% the of Ag(II) ions are coordinated only by F atoms in a square-planar fashion. The magnetic moments of Ag2+ from the same layer are almost perfectly antiferromagnetically aligned. Weak ferromagnetic interlayer interactions cause a small tilt (∼1.5°) of the magnetic moments, resulting in canted antiferromagnetism. Because of the lowering of the symmetry of [WOF5]- in the solid state, the vibrational spectra show more bands than expected for regular C4v symmetry. The electronic spectrum of Ag(WOF5)2 is reported and analyzed.

High-Pressure Behavior of Silver Fluorides up to 40 GPa.

A combined experimental-theoretical study of silver(I) and silver(II) fluorides under high pressure is reported. For AgI, the CsCl-type structure is stable to at least 39 GPa; the overtone of the IR-active mode is seen in the Raman spectrum. Its AgIIF2 sibling is a unique compound in many ways: it is more covalent than other known difluorides, crystallizes in a layered structure, and is enormously reactive. Using X-ray diffraction and guided by theoretical calculations (density functional theory), we have been able to elucidate crystal structures of high-pressure polymorphs of AgF2. The transition from ambient pressure to an unprecedented nanotubular structure takes place via an intermediate orthorhombic layered structure, which lacks an inversion center. The observed phase transitions are discussed within the broader framework of the fluorite → cotunnite → Ni2In series, which has been seen for other metal difluorides.

Local and Cooperative Jahn-Teller Effect and Resultant Magnetic Properties of M2AgF4 (M = Na-Cs) Phases.

The crystal structure, magnetic properties, heat capacity, and Raman spectra of double-perovskite M2AgF4 (M = K, K3/4Rb1/4, K1/2Rb1/2, K1/4Rb3/4, and Rb) phases have been examined, adding to the body of previous results for the M = Na, Cs derivatives. The results suggest that double-perovskite K2AgF4 adopts a disordered orthorhombic Bmab structure with an antiferrodistortive arrangement of the elongated and tilted [AgF6] octahedra rather than the structure with the ferrodistortive arrangement of compressed octahedra, as suggested previously (Mazej, Z.; Goreshnik, E.; Jaglicic, Z.; Gawel, B.; Lasocha, W.; Grzybowska, D.; Jaron, T.; Kurzydlowski, D.; Malinowski, P. J.; Kozminski, W.; Szydlowska, J.; Leszczynski, P. J.; Grochala, W. KAgF3, K2AgF4 and K3Ag2F7: important steps towards a layered antiferromagnetic fluoroargentate(II). CrystEngComm 2009, 11, 1702-1710). A re-examination of the previously collected single-crystal X-ray diffraction data confirms the current structure assignment, and it is also in agreement with recent theoretical calculations. High-field electron paramagnetic resonance spectra reaffirm the presence of elongated [AgF6] octahedra in the crystal structure of all M2AgF4 phases studied. The local structure of the M = K derivative is most complex, with regions of the sample that are quite orthorhombically distorted, whereas other regions more closely resemble the tetragonal phase. The mixed-cation K/Rb phases are also inhomogeneous, containing regions of the pure K compound and regions of another high-symmetry phase (likely tetragonal) of a mixed (Rb-richer) compound with unknown composition. The temperature-resolved phase diagram of all K/Rb phases has been established and positioned within the entire M = Na, K, Rb, Cs series.

Chemistry of silver(II): a cornucopia of peculiarities†.

Silver is the heavier congener of copper in the Periodic Table, but the chemistry of these two elements is very different. While Cu(II) is the most common cationic form of copper, Ag(II) is rare and its compounds exhibit a broad range of peculiar physico-chemical properties. These include, but are not limited to: (i) uncommon oxidizing properties, (ii) unprecedented large mixing of metal and ligand valence orbitals, (iii) strong spin-polarization of neighbouring ligands, (iv) record large magnetic superexchange constants, (v) ease of thermal decomposition of its salts with O-, N- or C-ligands, as well as (vi) robust Jahn-Teller effect which is preserved even at high pressure. These intriguing features of the compounds of Ag(II) will be discussed here together with (vii) a possibility of electromerism (electronic tautomerism) for a certain class of Ag(II) salts.

Novel ternary AgIICoIIIF5 fluoride: synthesis, structure and magnetic characteristics.

We present a new compound in the silver-cobalt-fluoride system, featuring paramagnetic silver (d9) and high-spin cobalt (d6), synthesized by solid-state method in an autoclave under F2 overpressure. Based on powder X-ray diffraction, we determined that AgIICoIIIF5 crystallizes in a monoclinic system with space group C2/c. The calculated fundamental band-gap falls in the visible range of the electromagnetic spectrum, and the compound has the character of charge-transfer insulator. AgCoF5 is likely a ferrimagnet with one predominant superexchange magnetic interaction constant between mixed spin cations (Ag-Co) of -62 meV (SCAN result). Magnetometric measurements conducted on a powdered sample allowed the identification of a transition at 128 K, which could indicate magnetic ordering.

Crystal structures and Raman spectra of imidazolium poly[perfluorotitanate(IV)] salts containing the [TiF6]2-, ([Ti2F9]-)∞, and [Ti2F11]3- and the new [Ti4F20]4- and [Ti5F23]3- anions.

Reactions between imidazole (Im, C3H4N2) and TiF4 in anhydrous hydrogen fluoride (aHF) in different molar ratios have yielded [ImH]2[TiF6]·2HF, [ImH]3[Ti2F11], [ImH]4[Ti4F20], [ImH]3[Ti5F23], and [ImH][Ti2F9] upon crystallization. All five structures were characterized by low-temperature single-crystal X-ray diffraction. The single-crystal Raman spectra of [ImH]4[Ti4F20], [ImH]3[Ti5F23], and [ImH][Ti2F9] were also recorded and assigned. In the crystal structure of [ImH]2[TiF6]·2HF, two HF molecules are coordinated to each [TiF6](2-) anion by means of strong F-H···F hydrogen bonds. The [Ti2F11](3-) anion of [ImH]3[Ti2F11] results from association of two TiF6 octahedra through a common fluorine vertex. Three crystallographically independent [Ti2F11](3-) anions, which have distinct geometries and orientations, are hydrogen-bonded to the [ImH](+) cations. The [ImH]4[Ti4F20] salt crystallized in two crystal modifications at low (α-phase, 200 K) and ambient (ß-phase, 298 K) temperatures. The tetrameric [Ti4F20](4-) anion of [ImH]4[Ti4F20] consists of rings of four TiF6 octahedra, which each share two cis-fluorine vertices, whereas the pentameric [Ti5F23](3-) anion of [ImH]3[Ti5F23] results from association of five TiF6 units, where four of the TiF6 octahedra share two cis-vertices, forming a tetrameric ring as in [Ti4F20](4-), and the fifth TiF6 unit shares three fluorine vertices with three TiF6 units of the tetrameric ring. The [ImH][Ti2F9] salt also crystallizes in two crystal modifications at low (α-phase, 200 K) and high (ß-phase, 298 K) temperatures and contains polymeric ([Ti2F9](-))∞ anions, which appear as two parallel infinite zigzag chains comprised of TiF6 units, where each TiF6 unit of one chain is connected to a TiF6 unit of the second chain through a shared fluorine vertex. Quantum-chemical calculations at the B3LYP/SDDALL level of theory were used to arrive at the gas-phase geometries and vibrational frequencies of the [Ti4F20](4-) and [Ti5F23](3-) anions, which aided in the assignment of the experimental vibrational frequencies of the anion series.

Synthesis and crystal structures of lanthanoid(III) hexafluoroarsenates with AsF3 ligands.

Lanthanoid(III) hexafluoroarsenates with AsF3 as a ligand were prepared with the reactions of solutions of Ln(AsF6)3 in anhydrous hydrogen fluoride and AsF3. Solid products with composition Ln(AsF3)3(AsF6)3 (Ln = La, Nd, Sm, Eu, Gd, Tb, Er, Tm) were isolated at 233 K. The attempt to prepare corresponding Yb and Lu compounds failed. Single crystals of Ln(AsF3)3(AsF6)3 (Ln = Ce, Pr) were prepared by the reaction of LnF3 (Ln = Ce, Pr) with AsF5 and aHF under solvothermal conditions above critical temperature of AsF5. During the crystallization the reduction of some AsF5 occurred and AsF3 was formed. Compounds crystallize in a hexagonal crystal system, space group P 6- 2c (a = 10.6656(7) Å (Ce); 10.6383(7) Å (Pr); c = 10.9113(9) Å (Ce), 10.878(2) Å (Pr); V = 1074.9(1) Å3 (Ce), 1066.2(2) Å3 (Pr); Z = 2). Ln atoms are coordinated by nine fluorine atoms in the shape of the tri-capped trigonal prism and are further connected in three-dimensional framework via trans bridging AsF6 units. Three fluorine atoms are provided by AsF3 (capped positions) and six by AsF6 units. X-ray powder analysis of Ln(AsF3)3(AsF6)3 (Ln = La, Nd, Sm, Eu, Gd, Tb, Er, Tm) show that they are isostructural with corresponding Ce and Pr compounds.

Surface passivation of natural graphite electrode for lithium ion battery by chlorine gas.

Surface lattice defects would act as active sites for electrochemical reduction of propylene carbonate (PC) as a solvent for lithium ion battery. Effect of surface chlorination of natural graphite powder has been investigated to improve charge/discharge characteristics of natural graphite electrode in PC-containing electrolyte solution. Chlorination of natural graphite increases not only surface chlorine but also surface oxygen, both of which would contribute to the decrease in surface lattice defects. It has been found that surface-chlorinated natural graphite samples with surface chlorine concentrations of 0.5-2.3 at% effectively suppress the electrochemical decomposition of PC, highly reducing irreversible capacities, i.e. increasing first coulombic efficiencies by 20-30% in 1 mol L-1 LiClO4-EC/DEC/PC (1:1:1 vol.). In 1 mol L-1 LiPF6-EC/EMC/PC (1:1:1 vol.), the effect of surface chlorination is observed at a higher current density. This would be attributed to decrease in surface lattice defects of natural graphite powder by the formation of covalent C-Cl and C=O bonds.

First Silver(I) - Complexes with Tetrazole Allyl Derivatives. Synthesis and Crystal Structure of [Ag2(C10H10N4S)2(H2O)2](BF4)2 and [Ag(C10H9ClN4S)(NO3)] π-Compounds (C10H10N4S and C10H9ClN4S - 5-(Allylthio)-1-phenyl- and 5-(Allylthio)-1-(4-chlorophenyl)-1H-tetrazole).

Crystalline silver(I) π complexes [Ag2(atpt)2(H2O)2](BF4)2 (1) (atpt - 5-(allylthio)-1-phenyl-1H-tetrazole (C10H10N4S)) and [Ag(atcpt)(NO3)] (2) (atcpt - 5-(allylthio)-1-(4-chlorophenyl)-1H-tetrazole (C10H9ClN4S)) complexes have been obtained using silver salt and the organic ligands. Compounds were characterized by X-ray single crystal diffraction: for 1 space group P21/n, a = 10.4560(5), b = 11.4008(5), c = 12.7550(7) Å, ß = 98.128(3)°, V = 1505.21(13) Å3 at 200 K, Z = 2; for 2: space group P21/a, a = 8.6790(8), b = 13.7324(10), c = 12.4597(13) Å, ß = 102.288(5)°, V = 1451.0(2) Å3 at 200 K, Z = 4. In both structures silver(I) atoms possess a trigonal pyramidal coordination environment with essentially different coordination modes of organic ligands. The Ag(I) arrangement in 1 involves the N3 and N4 atoms of two adjacent atpt molecules, an olefin C=C bond and a water molecule at the apical position. In crystal structure of 2 two O atoms from NO3- anions occupy two equatorial position of silver(I) coordination polyhedron, and atcpt is attached to the metal centre through the N4 atom of tetrazole core only. The weakly bound C=C bond is located at the apical position of Ag(I) environment.

Unexpected persistence of cis-bridged chains in compressed AuF3.

Raman scattering measurements indicate that cis-bridged chains are retained in AuF3 even at a compression of 45 GPa - in contrast to meta-GGA calculations suggesting that structures with such motifs are thermodynamically unstable above 4 GPa. This metastability implies that novel gold fluorides (e.g. AuF2) might be attainable at lower pressures than previously proposed.