Coordination Polyhedra OsXn(X = F, Cl, Br, I) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of compounds containing complexes [Os _a X _b ] ^z–(X = F, Cl, Br, I). Atoms of Os(V) at X = F and Cl, of Os(IV) at X = Cl, Br, and of Os(III) at X = Br were found to exhibit a coordination number of 6 with respect to the halogen atoms and to form OsX₆octahedra. The coordination polyhedra of Os(III) for X = Cl, I are square pyramids OsX₄. Each Os(III) atom forms one Os–Os bond; as a consequence, the OsBr₆octahedra share a face in forming Os₂Br^3– ₉complexes, while the OsX₄pyramids (X = Cl, I) dimerize to produce [X₄Os–OsX₄]^2–ions. The influence of the valence state of the Os atoms and of the nature of the halogen atoms on the composition and structure of the complexes formed and some characteristics of the coordination sphere of Os were considered.     

The Coordination Polyhedra PdX n (X = Cl,Br, I) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of 106 compounds containing palladium atoms surrounded by halogen atoms. Depending on the oxidation number (2 or 4), Pd atoms can bind 4 to 6 X atoms (X = Cl, Br, I) and form PdX _n coordination polyhedra shaped like octahedra or square pyramids (n = 6), square pyramids (n = 5), or squares (n = 4). A lone electron pair on Pd(II) was found on the basis of X-ray diffraction data. The influence of the palladium valence state on the key stereochemical features of palladium halide complexes is considered in terms of the 18-electron rule. The tendency of palladium atoms to Pd···H aghostic interactions was noted.     

Schwingungsspektren und Normalkoordinatenanalyse von (CF3)2SbX-Verbindungen (X = H,Cl, Br,I)

The gas phase i.r. and liquid phase Raman spectra of (CF₃)₂SbX (X = H, Cl, Br, I) have been investigated. The spectra are assigned on the basis of C_s local symmetry and a normal coordinate analysis making use of a transferred force field.     

Low energy electron energy-loss spectroscopy of CF3X (X=Cl,Br)

We report threshold electron energy-loss spectra for the fluorohalomethanes CF3X (X=Cl,Br). Measurements were made at incident electron energies of 30 and 100 eV in energy-loss range of 4-14 eV, and at scattering angles of 4 degrees and 15 degrees. Several new electronic transitions are observed which are ascribable to excitation of low-lying states as well as are intrinsically overlapped in the molecules themselves. Assignments of these electronic transitions are suggested. These assignments are based on present spectroscopic and cross-section measurements, high-energy scattering spectra, and ab initio molecular orbital calculations. The calculated potential curves along the C-X bond show repulsive nature, suggesting that these transitions may lead to dissociation of the C-X bond. The present results are also compared with the previous ones for CF3H, CF4, and CF3I.     

Coordination Polyhedra RhX6 (X = F,Cl, Br) in Crystal Structures

Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analyses of compounds containing complexes [Rh _a X _n ] ^z– (X = F, Cl, Br). It was found that, irrespective of oxidation number (+3, +4, or +5), rhodium atoms always exhibit the coordination number 6 with respect to the halogen atoms and have octahedral coordination. The influence of site symmetry and the valence state of Rh on the distortion of RhX₆ octahedra are considered. The electronic configuration of the Rh atoms is shown to influence the symmetry of their valence-force field within the crystal structure.     

Schwingungsspektren und Normalkoordinatenanalyse von (CF3)2PX und (CF3)2AsX (X = F,Cl, Br,J)

Vibrational Spectra and Normal Coordinate Analysis of (CF₃)₂PX and (CF₃)₂AsX (X = F, Cl, Br, I) Gas phase i. r. spectra and liquid-phase Raman spectra of (CF₃)₂AsX are reported. The i. r. investigation of the corresponding phosphorus compounds is complited. The spectra of both the phosphorus and the arsenic compounds were assigned on the basis of a normal coordinate analysis using a transferred force field.     

Synthesis,Crystal Structure,and Optical Properties of (CH3NH3)2CoX4 (X = Cl,Br, I,Cl0.5Br0.5, Cl0.5I0.5, Br0.5I0.5)

The reaction of methylammonium halides and cobalt halides yielded the organic‐inorganic hybrid compounds of general formula (CH₃NH₃)₂CoX₄. By varying the different halides, we were able to synthesize the whole row from Cl to I as well as some mixed halides compounds and to determinate the crystal structures. (CH₃NH₃)₂CoX₄ (X = Cl, Br, Cl_0.5Br_0.5, Br_0.5I_0.5) crystallize isotypic to (CH₃NH₃)₂HgCl₄ in space group P2₁/c with Z = 4 [X = Cl: a = 7.6483(9), b = 12.6885(18), c = 10.8752(12) Å, β = 96.639(9)°; X = Cl_0.5Br_0.5: a = 7.8271(9), b = 12.9543(9), c = 11.1007(11) Å, β = 96.320(8)°; X = Br: a = 7.9782(2), b = 13.1673(2), c = 11.2602(2) Å, β = 96.3260(10)° and X = Br_0.5I_0.5: a = 8.2435(12), b = 13.645(2), c = 11.5856(18) Å, β = 95.54(2)°]. The mixed halides show a statistic distribution in both cases. In (CH₃NH₃)₂CoCl₂I₂ an ordered variant is realized representing a new structure type [C2/m, Z = 4, a = 18.808(4), b = 7.3604(7), c = 10.4109(17) Å, β = 120.364(13)°]. (CH₃NH₃)₂CoI₄ crystallizes again isotypic to the respective mercury compound [(CH₃NH₃)₂HgCl₄] [Pbca, Z = 8, a = 10.9265(5), b = 12.1552(5), c = 20.9588(9) Å]. All structures are build up by inorganic tetrahedral [CoX₄]^2– anions and organic (CH₃NH₄)⁺ cations. Additionally the Raman spectra as well as the optical reflectance spectra are discussed.     

The IrX6 Coordination Polyhedra (X = F,Cl, Br) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of compounds containing [Ir _a X _b ] ^z– complexes (X = F, Cl, or Br). The coordination number of Ir atoms with respect to halogen atoms was found to be 6, irrespective of the oxidation state (III, IV, or V), and the coordination polyhedra formed by Ir were found to be always octahedra. The influence of the site symmetry and the valence state of the Ir atoms on the distortion of the IrX₆ octahedra is considered. It is shown that characteristics of the VDP of Ir atoms can be used for quantitative estimation of the crystal-chemical role of Ir atoms in the halide structures.     

Syntheses,Crystal Structures,and Vibrational Properties of Two Lead Azide Halides PbN3X (X = Cl,Br)

Abstract: Two new lead azide halides, PbN₃X (X = Cl, Br), were precipitated from aqueous solutions and structurally analyzed by both X-ray single-crystal/powder diffraction and vibrational spectroscopy, in addition to density-functional theory calculations. PbN₃Cl crystallizes in the monoclinic space group P2₁/m (no. 11) with a = 5.5039(11), b = 4.3270(9), c = 7.6576(15) Å, β = 101.28(3)° and adopts a structure with alternating layers of cations and anions. PbN₃Br crystallizes in the orthorhombic space group Pnma (no. 62) with a = 7.9192(2), b = 4.2645(1), c = 11.1396(3) Å, and the cations and anions are alternating crosswise. Within PbN₃Cl, a Pb²⁺ cation is surrounded by five azide and four chloride anions whereas, in PbN₃Br, the coordination consists of five azide and three bromide anions. Both structures contain chain-like [Pb₂X₂]²⁺ units with Pb–Cl = 2.95–3.21 Å and Pb–Br = 3.03–3.38 Å, and the N₃^– dumbbell is capped by five Pb²⁺ with Pb–N = 2.79–2.91 Å in PbN₃Cl and with Pb–N = 2.69–2.89 Å in PbN₃Br. The infrared and Raman spectra show the typical frequencies of a slightly asymmetric N₃^– unit, in good agreement with DFT phonon calculation. Thermal analyses reveal PbN₃Cl to be stable up to 290 °C before it explodes to yield PbCl₂, metallic Pb, and gaseous N₂.     

(Trifluoromethyl)germanes. Preparation and properties of (CF3)2GeHX (X = H,D, F,Cl, Br,I, CH3) and CF3GeHnX3-n (X = H,D, CF2H,CH3)

The hydrogenation of (CF₃)_nGeX_4-n (X = halogen, n = 1–3) with NaBH₄ in an acidic medium has been investigated. Deuteration with NaBD₄ and D₃PO₄ gave the partially deuterated species CF₃GeH_nD_3-n and (CF₃)₂GeH_nD_2-n in reasonable isotopic purity. The (CF₃)₂GeHBr was isolated and converted into the halides (CF₃)₂GeHX (X = F, Cl, I) by treatment with AgX or HX. Insertion of CF₂ into a GeH bond has been observed, and (CF₃)(CF₂H)GeH₂ has been characterized. Direct alkylation of GeH bonds was brought about by reaction with a mixture of RI and R′₂Zn (R, R′= CH₃, C₂H₅), and the methyl(trif]uoromethyl)germanes CF₃GeH₂(CH₃), CF₃GeH(CH₃)₂ and (CF₃)₂GeH(CH₃) were isolated. For R = CD₃, R′ = CH₃ the product distribution can be accounted in terms of two competing mechanisms.     

Ionization energies of LinX (n = 2, 3; X = Cl, Br, I) molecules

Molecules of Li(n)X (n = 2, 3; X = Cl, Br, I) were examined with a magnetic sector mass spectrometer by surface ionization using a triple rhenium filament impregnated with fullerene (C60). The ionization energies obtained for Li(2)Cl, Li(2)Br and Li(2)I molecules are 3.8 +/- 0.1, 3.9 +/- 0.1 and 4.0 +/- 0.1 eV, respectively. The first ionization energy of Li(2)Cl is documented, while there are no literature data for the ionization energies of Li(2)Br and Li(2)I. The molecules of Li(3)Cl, Li(3)Br and Li(3)I were detected experimentally for the first time with ionization energies of 4.0 +/- 0.1, 4.1 +/- 0.1 and 4.1 +/- 0.1 eV, respectively. The ionization energies of Li(n)X (n = 2, 3; X = Cl, Br, I) are in correlation with the theoretical prediction of their hyperlithiated configurations.     

Die Gadoliniumcarbidhalogenide Gd4C2X3 (X = Cl,Br)

The Gadolinium Carbide Halides, Gd₄C₂X₃ (X = Cl, Br) The compounds Gd₄C₂X₃ (X = Cl, Br) and Tb₄C₂Br₃ have been prepared by reaction of the metals (RE), REX₃, and C in sealed Ta capsules at 1 100° and 1 300°C, respectively. Monophasic samples of Gd₄C₂Br₃ and Tb₄C₂Br₃ were obtained by reacting stoichiometric mixtures of the starting materials for five days. The needle shaped crystals are bronze-coloured and sensitive to air and moisture. Gd₄C₂X₃ crystallizes in the space group Pnma (No. 62) with lattice constants a = 1 059.6(4), b = 368.4(1), c = 1 962.7(8) pm (Gd₄C₂Cl₃), a = 1 084.4(1), b = 373.0(1), c = 2 036.1(1) pm (Gd₄C₂Br₃). According to Guinier photographs, Tb₄C₂Br₃ is isotypic (a = 1 074.3(2), b = 370.6(1), c = 2 019.4(1) pm). In the crystal structure C is octahedrally coordinated by Gd. The Gd₆ octahedra are linked via common edges to form corrugated layers. The X-anions coordinate all free edges and corners of these layers and connect them via Xⁱ? Xⁱ contacts parallel [001]. Gd₄C₂Br₃ shows metallic conductivity. The magnetic susceptibility follows at high temperatures a Curie Weiss law with an effective moment of 7.95 μ_B. At temperatures below 50 K antiferromagnetic order is observed.     

Topological characterization of HXO2 (X = Cl, Br, I) isomerization

The isomerization reactions of HOOX --> HOXO --> HXO2 (X = Cl, Br, I) have been studied by using the density functional theory. The breakage and formation of the chemical bonds of the titled reactions have been discussed by the topological analysis method of electronic density. The calculated results show that there is a transitional structure of a three-membered ring on each of the isomerization reaction paths. The "energy transition state (ETS)" and the "structure transition state (STS)" in all of the studied reactions have been found. In all these reactions, the position of the structure transition state and the scope of the structure transition region correlate well with the reaction energy. The STS appears after the ETS in the exothermic reaction but it appears before the ETS in the endothermic reaction. The less reaction energy there is, the wider scope of the structure transition region.     

Tetramethylcyclotetraarsoxane Bridged Copper(I) Halides with Porous Sheet and Framework Structures [CuX{cyclo-(MeAsO)4}] (X=Cl,Br, I) and [Cu3X3{cyclo-(MeAsO)4}2] (X=Cl,Br)

Open sheet and framework structures [CuX{cyclo-(MeAsO)₄}] (X=Cl, Br, I) 1 – 3 and [Cu₃X₃{cyclo-(MeAsO)₄}₂] (X=Cl, Br) 4 and 5 may be prepared by self-assembly from CuX and methylcycloarsoxane (MeAsO)_n in acetonitrile solution. 1 – 3 exhibit 4⁴ nets in which (CuX)₂ units are connected through μ-1 _KAs¹ : 2 _KAs³ coordinated (MeAsO)₄ ligands into large 28-membered rings. In contrast, adjacent [CuX] chains in 4 and 5 are connected into sheets by μ₄-K⁴ As coordinated (MeAsO)₄ building blocks, with μ-1 _KAs¹ : 2 _KAs³ bridging of these layers by independent (MeAsO)₄ cyclotetramers leading to the generation of a porous framework structure. 1 – 5 were characterised by X-ray structural analysis.     

The reactions of K2ReX6 (X = Br OR I) and Re3X9 (X = Cl,Br OR I) with alkyl and aryl isocyanides

The reactions of alkyl isocyanides (RNC) and aryl isocyanides (ArNC) with the rhenium halides K₂ReX₆ (X = Br or I) and Re₃X₉ (X = Cl, Br or I) have been investigated. When the K₂Rex₆ salts are treated with neat isocyanide at room temperature, or with isocyanide ligands in polar solvents under reflux conditions, then the homoleptic isocyanide cations [Re(CNR)₆]⁺ or [Re(CNAr)₆]⁺, are isolated. Under less forcing conditions, various rhenium(III) and rhenium(I) species, e.g. [Re(CNCMe₃)₅I₂]⁺ and Re(CNAr)₅I, which may be considered as intermediates on the way to the formation of the homoleptic species, can be obtained. The rhenium(I) complexes Re(CNAr)₅I₃, which are believed to contain the coordinated triiodide ligand, have also been isolated and characterized. One route to these complexes is through the reaction of Re(CNAr)₅I with I₂. Reactions of the trinuclear halides Re₃X₉ (X = Cl, Br or I) with alkyl isocyanides at room temperature are found, in all instances, to provide adducts of the type Re₃X₉(CNR)₃. Under reflux conditions, Re₃Cl₉ and Re₃Cl₉(PEtPh₂)₃ react with Me₃CNC to fom products of cluster disruption, viz. [Re(CNCMe₃)₆]⁺ and [Re(CNCMe₃)₄(PEtPh₂)₂]⁺, respectively. The spectroscopic and electrochemical properties of complexes derived in this study are reported. These results are compared with those reported previously by Freni et al.     

[Pd(en)2Pd(en)2X2]4+n(X=Cl,Br,I)链的畸变研究

对一维卤桥过渡金属化合物〔Ｐｄ（ｅｎ）２Ｐｄ（ｅｎ）２Ｘ２〕ｎ＾４＋（Ｘ＝Ｃｌ,Ｂｒ,Ｉ）应用量子化学从头算及ＥＨＴ能带计算进行了研究,发现Ｐｅｉｅｒｌｓ畸变的产生及程度取决于填充轨道能量的降低与核间及电子间相互作用。     

Crystal structure of CF3I(Cl)F

In addition to CF3IF2 and CF3ICl2, CF3I(Cl)F is the only known example of the (trifluoromethyl)iodine dihalides. CF3I(Cl)F is even at low temperatures not stable in solution and decomposes by symmetrization. It crystallizes in the orthorhombic space group Cmca with a = 6.898(1) A, b = 7.310(1) A, c = 20.127(1) A and eight formula units per unit cell. The final R indices [I > 2 sigma(I)] are R1 = 0.0372 and wR2 = 0.0981.     

Scaled Quantum Mechanical Force Fields for the CF3SX Molecules (X = H,F, Cl,Br, I)

Density functional theory calculations at different levels of theory were performed on the molecules of the series CF₃SX (X = H, F, Cl, Br, I) in order to obtain their optimized geometric parameters and conformations, the wavenumbers corresponding to the normal modes of vibrations and the associated force constants. The obtained force fields were transformed to local symmetry coordinates and scaled to reproduce the experimental wavenumbers.     

Theoretical study and rate constants calculation for the reactions X + CF3CH2OCF3 (X = F,Cl, Br)

The multiple‐channel reactions X + CF₃CH₂OCF₃ (X = F, Cl, Br) are theoretically investigated. The minimum energy paths (MEP) are calculated at the MP2/6‐31+G(d,p) level, and energetic information is further refined by the MC‐QCISD (single‐point) method. The rate constants for major reaction channels are calculated by canonical variational transition state theory (CVT) with small‐curvature tunneling (SCT) correction over the temperature range 200–2000 K. The theoretical three‐parameter expressions for the three channels k_1a(T) = 1.24 × 10^?15T^1.24exp(?304.81/T), k_2a(T) = 7.27 × 10^?15T^0.37exp(?630.69/T), and k_3a(T) = 2.84 × 10^?19T^2.51 exp(?2725.17/T) cm³ molecule^?1 s^?1 are given. Our calculations indicate that hydrogen abstraction channel is only feasible channel due to the smaller barrier height among five channels considered. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2012     

Schwingungs-Raman-Spektren von Hexahalogenokomplexen von OsIV (X = Cl,I) und IrIV (X = Cl,Br) bei 80 K

Vibrational Raman Spectra of Hexahalo Complexes of Os^IV (X = Cl, I) and Ir^IV (X = Cl, Br) at 80 K The Resonance-Raman (RR) spectra of the tetrabutyl- resp. tetraethylammonium salts of [OsCl₆]^2?, [OsI₆]^2?, [IrCl₆]^2?, and [IrBr₆]^2? have been investigated with the excitation-lines of an Ar⁺ and Kr⁺ laser. Devices with a movable sample holder for low-temperature experiments (80 K) are described. The anormal intensities of some of the Ra-active fundamentals are attributed to the RR effect. As a rule the deformation vibration υ₅(T_2g) is RR enhanced if excited within a π—π*(dt_2g)-CT-transition and the stretching vibration υ₂(E_g) is RR-enhanced within a π—σ*(de_g)-CT-transition. The dispersion of the degree of depolarisation of the three Ra-active fundamentals of [IrBr₆]^2? demonstrates, that this rule cannot only be applicated to the symmetrical but also to the antisymmetrical part of the scattering tensor.