Structure of Aqueous Gallium(III) Bromide Solutions Over a Temperature Range 80–333 K by Raman Spectroscopy, X-ray Absorption Fine Structure, and X-ray Diffraction

The structure and complex formation of concentrated aqueous gallium(III) bromide (GaBr₃) solutions have been investigated over a temperature range 80–333 K by Raman spectroscopy, X-ray absorption fine structure (XAFS), and X-ray diffraction. The Raman spectra obtained at various [Br^?]/[Ga³⁺] molar ratios and temperatures have shown that complex formation between Ga³⁺ and Br^? occurs as a predominant species, with [GaBr₄]^? at [Ga³⁺] as high as 1～2 M (M = mol?dm ^?3) and [Br^?]/[Ga³⁺] ratios > ～2, and that cooling of the solutions favors the formation of the aqua Ga³⁺. The intermediate species were not seen in the Raman spectra. The XAFS data have revealed that the aqua complex has a sixfold coordination as [Ga(H₂O)₆]³⁺ with a Ga³⁺–H₂O distance of (1.96 ± 0.02) Å, whereas the [GaBr₄]^? complex has a Ga³⁺–Br^? distance of (2.33± 0.02) Å, and that vitrification of the aqueous GaBr₃ solution at liquid nitrogen temperature shifts the equilibrium toward the aqua complex. The X-ray diffraction data at different subzero temperatures have shown a tendency of decreasing Ga³⁺–Br^? and increasing Ga³⁺–H₂O interactions with lowering temperature, confirming the preference of aqua Ga³⁺ in the supercooled liquid state as well as in the glassy state. The Ga³⁺–H₂O distance of ～1.8 Å for the tetrahedral coordination was found in a 2.01 M gallium(III) bromide solution with a [Br^?]/[Ga³⁺] ratio of 3.7 and gradually increased to a value of 1.92 Å for octahedral geometry with decreasing temperature, suggesting that equilibrium shifts from [GaBr₄]^? to [Ga(H₂O)₆]³⁺ through intermediate species, [GaBr _n ]^(3?n)+ (n = 2 and 3). The Ga³⁺–Br^? and Br^?–Br^? distances within [GaBr₄]^? with an almost tetrahedral symmetry are (2.35± 0.02) and (3.82± 0.03) Å, respectively. The Ga³⁺ has the second hydration shell at (4.03± 0.03) Å and the hydration of Br^? is characterized with a Br^?–H₂O distance of (3.35± 0.02) Å at all temperatures investigated.     

A new radical cation salt bis(ethylenedithio)tetrathiafulvalene with [Pt(NO2)4]2− anion: Synthesis, structure, and conductivity

A radical cation salt based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) containing the [Pt(NO₂)₄]^2? anion was synthesized for the first time. The crystal and molecular structure of this salt, (BEDT-TTF)₂Pt(NO₂)₄, was established by X-ray diffraction analysis. The crystal structure consists of radical cation BEDT-TTF layers between which planar-square anions [Pt(NO₂)₄]^2? are located. The layers are formed by BEDT-TTF stacks built of dimers. The interplanar distances within the dimers and between them are 3.41 and 3.96 Å, respectively. The distribution of the bond lengths and bond angles in BEDT-TTF corresponds to the charge of the cation +1. The room-temperature conductivity of (BEDT-TTF)₂Pt(NO₂)₄ is 3·10^?3 Ω^?1 cm^?1, and the temperature dependence of the conductivity exhibits the semiconducting character.     

Synthesis,structures and magnetic properties of nickel bis (dithiolene) complexes with [Fe(qsal)2]+

Two new compounds containing the possible Fe(III) spin-crossover cation, [Fe(qsal)₂]⁺ (qsalH = N-(8-quinolyl)salicylaldimine), and nickel bis(dithiolene) anions have been synthesized. Both are 1 : 1 salts [Fe(qsal)₂][Ni(dddt)₂] · CH₃CN · CH₃OH (1) and [Fe(qsal)₂][Ni(pddt)₂] (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate; pddt = 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate). They have been characterized by X-ray crystal structure determination, elemental analysis, UV-Vis spectra and magnetic susceptibility measurements. The UV–Vis spectra are dominated by [Ni(L)₂]^? (1, L = dddt; 2, L = pddt). Magnetic studies show antiferromagnetic interaction in 1 from intermolecular S···S contacts and π–π stacking interactions, while the antiferromagnetic interaction in 2 is very weak.     

N-methyl-2,2′-bipyridylium ion (bpyMe) complexes: Synthesis and cyclometallation of [Pd(bpyMe)2Cl2]2+

On prolonged heating in water Pd(bpyMe)Cl₃ (bpyMe = N-methyl-2,2′-bipyridylium cation) cyclometallates to give monomeric Pd(bpyMe-H)Cl₂, whereas the immediate products are a mixture of trans-[Pd(bpyMe)₂Cl₂]²⁺ and anionic palladium species. [Pd(bpyMe)₂Cl₂]²⁺ was synthesised directly from Na₂PdCl₄ and on heating gives Pd(bpyMe-H)Cl₂ with the elimination of bpyMe and H⁺.     

Synthesis and Crystal Structures of New Palladium(II)—Gallium(III) Complexes with Bridging Halogenide Ligands

The reaction of palladium(II) bromide or palladium(II) iodide with the respective gallium(III) halogenide in the presence of aromatic solvents leads to the formation of palladium(II) tetrabromo— and tetraiodogallate. The compounds are isostructural {monoclinic, C2/m, Pd[GaBr₄]₂: a = 1267(2), b = 808(1), c = 722(1) pm, β = 94.5(1)°; Pd[GaI₄]₂: a = 1363(1), b = 849.9(4), c = 756.6(7) pm, β = 95.38(3)°}. The structures contain mononuclear complexes Pd[GaX₄]₂, where X^— = Br^— ( 1 ), I^— ( 2 ). The crystal structures of 1 and 2 were determined by single‐crystal X‐ray diffraction. Crystals of both compounds turned out to be similarly twinned.     

Molten Salt Synthesis, Crystal Structure and Optical Properties of a Novel Quaternary Metal Selenide, K2AgIn3Se6

K2AgIn3Se6 was synthesized by a molten-salt (alkali-metal polyselenide flux) reaction at 500 ℃. The orange red granular crystal crystallizes in monoclinic space group C2/c with cell parameters, a=1.16411(7) nm, b=1.16348(8) nm, c=2.14179(12) nm, V=2.8740(9) nm^3, and Z=8. The crystal has a new two-dimensional structure containing ^2∞[AgIn3Se6]^2- anionic layers separated by K^- cations and the ^2∞[AgIn3Se6]^2- layer is constructed with corner-shared [AgSe4] and [InSe4] tetrahedra. The optical band gap of K2AgIn3Se6 was determined to be ca. 2.9 eV by UV/vis/NIR diffuse reflectance spectra.     

Molecular Conductors Based on M(dddt)2 Bisdithiolene Cation Complexes

The synthesis, structure and properties of molecular conductors based on M(dddt)₂ cation complexes (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) which are metal complex analogs of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) salts are considered. Formally, the central C=C bond of ET is substituted by a metal ion in the M(dddt)₂ complexes. The effect of metal (M=Ni, Pt, Pd) and counterion on crystal structure and conducting properties of M(dddt)₂ complexes is analyzed. The similarity and distinction in structures and properties of M(dddt)₂ and ET salts are discussed.     

Chiral anionic layers in tartramide spiroborate salts and variable solvation for [NR4][B(TarNH2)2] (R = Et,Pr or Bu)

The spiroborate anion, namely, 2,3,7,8‐tetracarboxamido‐1,4,6,9‐tetraoxa‐5λ⁴‐boraspiro[4.4]nonane, [B(TarNH₂)₂]^?, derived from the diol l ‐tartramide TarNH₂, [CH(O)(CONH₂)]₂, shows a novel self‐assembly into two‐dimensional (2D) layer structures in its salts with alkylammonium cations, [NR₄]⁺ (R = Et, Pr and Bu), and sparteinium, [HSpa]⁺, in which the cations and anions are segregated. The structures of four such salts are reported, namely, the tetrapropylazanium salt, C₁₂H₂₈N⁺·C₈H₁₂BN₄O₈^?, the tetraethylazanium salt hydrate, C₈H₂₀N⁺·C₈H₁₂BN₄O₈^?·6.375H₂O, the tetrabutylazanium salt as the ethanol monosolvate hemihydrate, C₁₆H₃₆N⁺·C₈H₁₂BN₄O₈^?·C₂H₅OH·0.5H₂O, and the sparteinium (7‐aza‐15‐azoniatetracyclo[7.7.1.0^2,7.0^10,15]heptadecane) salt as the ethanol monosolvate, C₁₅H₂₇N₂⁺·C₈H₁₂BN₄O₈^?·C₂H₅OH. The 2D anion layers have preserved intermolecular hydrogen bonding between the amide groups and a typical metric repeat of around 10 × 15 Å. The constraint of matching the interfacial area organizes the cations into quite different solvated arrangements, i.e. the [NEt₄] salt is highly hydrated with around 6.5H₂O per cation, the [NPr₄] salt apparently has a good metric match to the anion layer and is unsolvated, whilst the [NBu₄] salt is intermediate and has EtOH and H₂O in its cation layer, which is similar to the arrangement for the chiral [HSpa]⁺ cation. This family of salts shows highly organized chiral space and offers potential for the resolution of both chiral cations and neutral chiral solvent molecules.     

Structure of the neutral metal complex Pt(dddt)2

A neutral metal complex, [Pt(dddt)₂]° (1), has been obtained by oxidation of the [Pt(dddt)₂]^– anion with excess (Bu₄N)AuBr₄ in nitrobenzene. Crystallographic data for 1a=17.854(9) Å,b=18.409(9) Å,c=4.717(5) Å, =68.83(2)°, space group P2₁/n,Z=4,d _calc=2.55 g/cm³. In1 two independent centrosymmetric [Pt(dddt)₂]° molecules are packed in stacks that form layers parallel to the (110) plane. The molecules of1 in the layers have shortened S...S contacts 3.491(9) Å, and 3.594(10) Å. The average bond lengths Pt-S 2.242(7) Å, S-C 1.71(2) Å and C=C 1.40(3) Å, together with the square-planar coordination of Pt in PtS₄, suggest considerable conjugation in the metal cycles.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1207–1209, July, 1993.     

A Homoleptic KrF2 Complex, [Hg(KrF2)8][AsF6]2⋅2 HF

The reaction of Hg(AsF₆)₂ with a large molar excess of KrF₂ in anhydrous HF has afforded the first homoleptic KrF₂ coordination complex of a metal cation, [Hg(KrF₂)₈][AsF₆]₂?2 HF. The [Hg(KrF₂)₈]²⁺ dication is well‐isolated in the low‐temperature crystal structure of its HF‐solvated [AsF₆]^? salt, and consists of eight KrF₂ molecules that are terminally coordinated to Hg²⁺ by means of Hg?F(KrF) bonds to form a slightly distorted, square‐antiprismatic coordination sphere around mercury. The Raman spectrum of [Hg(KrF₂)₈]²⁺ was assigned with the aid of calculated gas‐phase vibrational frequencies. Computational studies indicate that both electrostatic and orbital interactions are important for metal–ligand bonding and provide insight into the geometry of the [Hg(KrF₂)₈]²⁺ cation and the nature of noble‐gas difluoride ligand bonding.     

Quantum chemical calculations of stability constants: study of ligand effects on the relative stability of Pd(II)�Cpeptide complexes

Replacement of [Pd(H₂O)₄]²⁺ by cis-[Pd(en)(H₂O)₂]²⁺, [PdCl₄]^2?, and [Pd(NH₃)₄]²⁺ on the hydrolytic cleavage of the Ace-Ala-Lys-Tyr-Gly?CGly-Met-Ala-Ala-Arg-Ala peptide is theoretically investigated by using different quantum chemical methods both in the gas phase an in water solution. First, we carry out a series of validation calculations on small Pd(II) complexes by computing high-level ab initio [MP2 and CCSD(T)] and Density Functional Theory (B3LYP) electronic energies while solvent effects are taken into account by means of a Poisson-Boltzmann continuum model coupled with the B3LYP method. After having assessed the actual performance of the DFT calculations in predicting the stability constants for selected Pd(II)-complexes, we compute the relative free energies in solution of several Pd(II)?Cpeptide model complexes. By assuming that the reaction of the peptide with cis-[Pd(en)(H₂O)₂]²⁺, [Pd(Cl)₄]^2?, and [Pd(NH₃)₄]²⁺ would lead to the initial formation of the respective peptide-bound complexes, which in turn would evolve to afford a hydrolytically active complex [Pd(peptide)(H₂O)₂]²⁺ through the displacement of the en, Cl^?, and NH₃ ligands by water, our calculations of the relative stability of these complexes allow us to rationalize why [Pd(H₂O)₄]²⁺ and [Pd(NH₃)₄]²⁺ are more reactive than cis-[Pd(en)(H₂O)₂]²⁺ and [PdCl₄]^2? as experimentally found.     

Synthesis and crystal structure of 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane bis(hydrogen oxalate)

A crystalline salt of 2.2.2-cryptand and oxalic acid, 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane bis(hydrogen oxalate), [H₂(Crypt-222)]²⁺·2(C₂HO₄)^?, was synthesized and studied by single crystal X-ray diffraction. In the crystal structure of this salt, the 2.2.2-cryptand cation has a rare conformation of the exo-exo type in which the H atoms at the two protonated N atoms are oriented outside the cryptand cavity. The geometric parameters (bond lengths, bond angles, torsion angles) of the [H₂(Crypt-222)]²⁺ cation and two independent C₂HO ₄ ^? anions were found with a fairly high accuracy, and the crystal packing was determined. These ions are linked by interionic hydrogen bonds to form thick infinite layers parallel to the (xz) plane.     

Room-Temperature Synthesis of the Bi5[GaCl4]3 Salt From Three Different Classes of Ionic Liquids

Following the development in the synthesis of subvalent cluster compounds, we report on the use of three different classes of room-temperature ionic liquids for the synthesis of the pentabismuth-tris(tetragallate) salt, Bi₅[GaCl₄]₃, characterized by X-ray diffraction. The Bi₅[GaCl₄]₃ salt was prepared by reduction of BiCl₃ using gallium metal in ionic liquid reaction media containing a strong Lewis acid, GaCl₃. The ionic liquids; trihexyltetradecyl phosphonium chloride [Th-Td-P⁺]Cl^?, 1-dodecyl-3-methylimidazolium chloride [Dod-Me-Im⁺]Cl^? and N-butyl-N-methylpyrrolidinium chloride [Bu-Me-Pyrr⁺]Cl^? from three of the main classes of ionic liquids were used in synthesis. Reactions using ionic liquids composed of the trihexyltetradecyl phosphonium cation [Th-Td-P⁺] and the anions; tetrafluoroborate [BF₄ ^?], bis(trifluoro-methyl sulfonyl) imide [(Tf)₂N^?] and hexafluorophosphate [PF₆ ^?] were also investigated.     

Structural Diversity in Thallium Chemistry. Part V

From thallium(III) bromide solution, the unsubstituted pyridinium cation yields a complex ( 1 ) with the [Tl₂Br₉]^3? anionic stoichiometry. The Raman spectrum and single‐crystal X‐ray crystallographic analysis showed that the salt contains independent [TlBr₄]^? and bromide anions. A variety of mono‐ and disubstituted pyridinium cations were also employed in similar syntheses. The 2‐bromopyridinium cation gave a salt 2 with [TlBr₅]^2? stoichiometry, but the crystal structure revealed very weakly interacting [TlBr₄]^? and bromide anions with a Tl ???Br^? distance of 4.1545(6) Å. The 2‐(ammoniomethyl)pyridinium and 2‐amino‐4‐methylpyridinium cations yielded complexes containing [TlBr₅]^2? ( 3 ) and [TlBr₄]^? ( 4 ) species, respectively, which were confirmed by Raman spectroscopy and X‐ray crystallographic analyses. For 3 , the [TlBr₅]^2? anion has a highly distorted trigonal bipyramidal conformation with one long axial Tl ???Br bond of 3.400(2) Å. Microanalytical results in conjunction with Raman spectra from a further five salts confirmed that they all contain the simple [TlBr₄]^? anion. N? H ???Br Hydrogen bonds clearly influence the nature of the anionic species obtained in these systems.     

Structure and vaporization of a gallium tribromide aminomethylpyridine complex

The structure of a gallium tribromide complex with 2-aminomethylpyridine (amPy) (1: 1) has been established by single-crystal X-ray diffraction for the first time. The complex has been shown to have the ionic structure [GaBr₂amPy₂]⁺[GaBr₄]^? in the condensed phase. The qualitative composition of the vapor over the complex has been determined by mass spectrometry within a temperature range of 80–250°C. The elimination of hydrogen bromide and 2-aminomethylpyridine proceed at 80–180°C to enrich the condensed phase with gallium tribromide. GaBr₂(amPy-H), GaBr₃amPy, GaBr(amPy-2H), and Ga₂Br₅(amPy-H) are the major gallium-containing vapor species at 250°C.     

Preparation and crystal structure of bis(triethylene glycol-<Emphasis Type="Italic">O</Emphasis>,<Emphasis Type="Italic">O</Emphasis>′,<Emphasis Type="Italic">O</Emphasis>′’,<Emphasis Type="Italic">O</Emphasis>‴)manganese(II) dibromide

A new complex, bis(triethylene glycol-O,O′,O′’,O?)manganese(II) dibromide [Mn(TEG)₂]²⁺·2Br^?, was prepared. Its structure was studied by single crystal X-ray diffraction. The complex cation [Mn(TEG)₂]²⁺ is of the host-guest type with two TEG ligands (podands) as hosts. Both TEG ligands are disordered and tetradentate, with all the four oxygen atoms of each ligand participating in the coordination. The Mn²⁺ cation has coordination number 8, and its coordination polyhedron is a distorted bisdisphenoid (trigonal dodecahedron). The geometric parameters (bond lengths, bond and torsion angles) of the complex were determined relatively accurately. In the crystal structure, the ions form infinite thick layers by interionic hydrogen bonds O-H···Br^?.     

Transfer of the chelating ligands in the systems [LAuCl2]+-[PdCl4]2−: Synthesis and structure of the salt (NH4)0.20[(Bipy)AuCl2]1.04[(Bipy)PdCl2]0.96[AuCl4]0.76[PdCl4]0.24

The formation of binary complex salts containing gold(III) in the cation and palladium(II) in the anion in the systems [(Bipy)AuCl₂]⁺-[PdCl₄]^2? occurs by transfer of the N,N-electron-donating chelating ligand bipyridine and the chloride ligands between the gold-containing cation and the palladium-containing anion. The resulting neutral salt [(Bipy)PdCl₂] crystallizes together with the anion [AuCl₄]^? from acetonitrile-water (1 : 1-1 : 2, v/v) to give the complex salt (NH ₄ ⁺ )_0.20[(Bipy)AuCl ₂ ⁺ ]_1.04[(Bipy)PdCl₂]_0.96[AuCl ₄ ^? ]_0.76PdCl ₄ ^2? ]_0.24 with a total Au : Pd ratio of 3 : 2. The ammonium cation is formed from acetonitrile upon its hydrolysis most likely catalyzed by Pd complexes. Quantum-chemical calculations were performed to study the transfer of the chelating ligand theoretically.     

A New Paramagnetic Pd(dmit)2 Salt: Tris(2,2′-Bipyridine)Nickel(II) Bis(1,3-Dithiole-2-Thione-4,5-Dithiolato)Palladate(II) Mono-Acetonitrile; [Ni(bpy)3][Pd(dmit)2]·CH3CN

Combination of the [Ni(bpy)₃]²⁺ cation complex and the [Pd(dmit)₂]⁻ anion (dmit=C₃S₅²⁻=1,3-dithiole-2thione-4,5-dithiolate) has resulted in the paramagnetic [Ni(bpy)₃][Pd(dmit)₂]·CH₃CN compound, a suitable precursor for a molecular magnetic conductor. Its crystal structure consists of a Pd(dmit)₂ anion arrangement that is quite different from segregated stack layers often found for M(dmit)₂−based compounds. The reduction of the [Pd(dmit)₂]^- to the 2− charged anion in the title compound most probably is the result of a charge disproportionation between Pd(dmit)₂ anions.     

An ion-pair complex [TTF][Pd(mnt)2]: synthesis,crystal structure,magnetic property,and electrical conductivity

A new ion-pair complex, [TTF][Pd(mnt)₂] (1), where TTF⁺ =?tetrathiafulvalene and mnt^2??=?maleonitriledithiolate, was synthesized and characterized structurally. Compound 1 crystallizes in triclinic space group P-1, with a?=?8.008(5)?Å, b?=?11.333(8)?Å, c?=?11.373(6)?Å, α?=?108.112(7)°, β?=?91.550(5)°, γ?=?95.232(5)°, and V?=?975.2(11)?ų. The [TTF]⁺ cations (C) and [Pd(mnt)₂]^? anions (A) form mixed stacks in …AACCAACC… fashion, and the neighboring mixed stacks are held together via van der Waals forces in the crystal. Compound 1 shows weak Curie/Weiss-type magnetic behavior from 2 to 370?K; theoretical investigation disclosed the existence of strongly antiferromagnetic coupling in both [Pd(mnt)₂]₂ ^2? and [TTF]₂ ²⁺ dimer pairs via frontier orbitals overlap mechanism and weakly ferromagnetic coupling between the face-to-face overlapped [TTF]⁺ and [Pd(mnt)₂]^? via spin polarization mechanism within a mixed stack. The powdered pellet electrical conductivity measurement indicated that 1 shows semiconductor character with activation energy of 1.1(3)?eV.     

The crystal structure of a complex barium,aluminium, copper(II) fluoride: Ba4Cu2Al3F21

Ba₄Cu₂Al₃F₂₁ is orthorhombic : a = 5.299(1) Å, b = 7.318(1) Å, c = 41.529(7) Å, Z = 4. The crystal structure was solved in the space group P2₁2₁2₁ (n^o19) from X-ray single crystal data using 5682 unique reflections (3698 with F_O/σ(F) > 4). It consists in a succession along c of 8 layers of 2 different types of sheets. The first layer, formulated [Cu₂AlF₁₁]⁴⁻ in which copper-fluorine octahedra are linked by edges to form infinite distorted chains connected together by aluminium-fluorine octahedra, is followed by two [Al₂F₁₀]⁴⁻ layers of infinite cischains of aluminium-fluorine octahedra linked by two vertices and another [Cu₂AlF₁₁]⁴⁻ layer. These 4 layers are doubled along c by one of the screw-axes 2₁. The barium ions, 12-coordinated, are inserted between the sheets.