Chalkogenid-Disilicate der Lanthanoide vom Typ M4X3[Si2O7] (M  Ce?Er; X  S,Se)

M₄X₃[Si₂O₇]-Type Lanthanide Chalcogenide Disilicates (M ? Ce? Er; X ? S, Se) Attempts to produce single crystals of MSe₂ (or MSe^2?X) by vapour phase transport with iodine or the oxidation of MCl₂ (or MClH) with sulfur in the presence of NaCl in sealed evacuated quartz containers often yielded well-grown single crystals with the composition M₄X₃[Si₂O₇] (M ? pr, Sm, Gd, X ? Se, and M ? Nd, Er, X ? S) as by-products. The crystal structures (tetragonal, 14₁/amd (no. 141)), Z = 8, contain two crystallographically independent M₃₊ Cations that are interconnected by chalcogenide (X_2?) and disilicate anions ([Si₂O₇]^6?). (M1)³⁺ is surrounded by eight (five X^2? and three terminal O_2? of the disilicate group), (M2)³⁺ by nine (three X^2? and six terminal O^2? of the [Si₂O₇]_6? anion) chalcogenide anions. The disilicate anion itself exhibits the eclipsed conformation with non-linear Si? O? Si bridges (angles: 128 – 133°).     

ChemInform Abstract: X2Y2 Isomers: Tuning Structure and Relative Stability Through Electronegativity Differences (X: H,Li, Na,F, Cl,Br, I; Y: O,S, Se,Te).

Density functional calculations on XYYX and X₂YY isomers of the X₂Y₂ species (X: H, Li, Na, F, Cl, Br, I; Y: O, S, Se, Te) show that the XYYX isomers are more stable than the X₂YY forms except for X = F and Y = S and Te, for which the F₂SS and F₂TeTe isomers are slightly more stable.     

β‐Tl2SO4

The ambient‐temperature form of dithallium sulfate, β‐Tl₂SO₄, is similar to β‐K₂SO₄ and is characterized by isolated sulfate tetrahedra and two different thallium sites with coordination numbers 9 and 11. All the atoms, except one O atom, lie on mirror planes. In spite of there being a high concentration of Tl⁺ cations, the stereochemical activity of the 6s² pairs is low, similar to that of isotypic Tl₂XO₄ compounds (X = Cr and Se). This behaviour is the consequence of both weak Tl—O bonds and strong X—O bonds, because in a Tl—O—X linkage the electronic cloud of the O²⁻ anion is strongly distorted and displaced towards X, resulting in a low negative charge in the face of the Tl atom. Consequently, the Coulombic repulsions between the lone pair and the O²⁻ anions are weak. All of the Tl₂XO₄ compounds exhibit the same open packing of A⁺ cations and [XO₄]²⁻ anions as their isotypic alkali counterparts.     

Neue Heteropolyanionen des M2X2W20‐Typs mit Antimon(III) als Heteroatom

New Heteropolyanions of the M₂X₂W₂₀ Structure Type with Antimony(III) as a Heteroatom The syntheses of two new heteropolyanions of the M₂X₂W₂₀ structure type are presented. They are characterized by X‐ray structure analysis and vibrational spectra. Na₆(NH₄)₄[Zn₂(H₂O)₆(WO₂)₂(SbW₉O₃₃)₂]·36H₂O (1) is monoclinic (P2₁/n) with a = 12.873(3)Å, b = 25.303(4)Å, c = 15.975(4)Å and β = 91.99(3)°. Na₁₀[Mn₂(H₂O)₆(WO₂)₂(SbW₉O₃₃)₂]·40H₂O (2) also crystallizes in the space group P2₁/n with a = 12.892(3)Å, b = 25.219(5)Å, c = 16.166(3)Å and β = 94.41(3)°. Both polyanions are isostructural to anions of this structure type containing other heteroatoms. They are built up by two β‐B‐SbW₉ fragments, which are derived from defect structures of the Keggin anion. These subÍunits are connected by two formal WO₂ groups with further stabilization by addition of two M(H₂O)₃ groups (M = Zn^II, Mn^II, Fe^III, Co^II) leading to the M₂X₂W₂₀‐type heteropolytungstates.     

Geometries,vibrational frequencies,and electron affinities of X2Cl (X=C,Si,Ge) clusters

Ab initio quantum chemical calculations have been performed on X₂Cl^? and X₂Cl (X = C, Si, Ge) clusters. The geometrical structures, vibrational frequencies, electronic properties and dissociation energies are investigated at the Hartree–Fock (HF), Møller–Plesset second‐ and fourth‐order (MP2, MP4), CCSD(T) level with the 6‐311+G(d) basis set. The X₂Cl (X = C, Si, Ge) and X₂Cl^? (X = Si, Ge) take a bent shape obtained at the ground state, while C₂Cl^? has a linear structure. The impact on internal electron transfer between the X₂Cl and the corresponding anional clusters is studied. The three different types of electron affinities (EAs) at the CCSD(T) are reported. The most reliable adiabatic electronic affinities, obtained at the CCSD(T)/cc‐pvqz level of theory, are predicted to be 3.30, 2.62, and 1.98 eV for C₂Cl, Si₂Cl, and Ge₂Cl, respectively. The calculated EAs of C₂Cl and Ge₂Cl are in good agreement with theoretical results reported. The correlation effects and basis sets effects on the geometrical structures and dissociation energies are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Theoretical study of polyoxide clusters B20O30, Al20O30, V20O50, Si20O30H20, and Si20O30F20

The structural, electronic, and vibrational characteristics and energies of the isolated polyoxide clusters B₂₀O₃₀, Al₂₀O₃₀, V₂₀O₅₀, Si₂₀O₃₀H₂₀, and Si₂₀O₃₀F₂₀ and their complexes with the H⁻ ion and ammonia complexes Al₂₀O₃₀ · nNH₃ have been calculated by the density functional theory B3LYP method with different basis sets. The computation results show that the symmetric closo structure I _h with oxygen bridges located above the centers of the faces of an empty [M₂₀] dodecahedron is more favorable for V₂₀O₅₀, Si₂₀O₃₀H₂₀, and Si₂₀O₃₀F₂₀. For B₂₀O₃₀, the cage closo isomer is also more favorable than the other isomers, but its structure is severely distorted as compared to a dodecahedron and has a symmetry close to C ₃ . For Al₂₀O₃₀, the I _h structure corresponds to a high-lying local minimum of the potential energy surface. For Al₂₀O₃₀, a set of unusual puckshaped isomers of symmetry C _i , with different numbers of four-coordinate atoms ^IVAl and three-coordinate atoms ^IIIO, was localized; these structures are more than 90 kcal/mol more favorable than the dodecahedron I _h . The most favorable isomer of Al₂₀O₃₀ contains twelve four-coordinate atoms ^IVAl and four five-coordinate atoms ^VAl. The energies of dissociation of the most favorable M₂₀O₃₀ clusters into the M₂O₃ (C _2v ) and M₄O₆ (T _d ) fragments and, in the case of Al₂₀O₃₀, also into the Al₈O₁₂ (O _h ) and Al₁₂O₁₈ (D _3d ) fragments, have been estimated. The conclusion has been drawn that these clusters can, in principle, exist and can be experimentally detected in the isolated state. Analogous calculations have been performed for ammonia complexes Al₂₀O₃₀ · nNH₃ with n varying from 1 to 20. The effect of solvation on the relative stability of the dodecahedral and puckshaped isomers of the Al₂₀O₃₀ cluster is observed. The isomers with ammonia molecules in their first coordination sphere become much closer to one another on the energy scale; however, the dodecahedron remains a considerably less favorable intermediate. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 4, pp. 624–635.     

Strukturen von neuen Bis(pentafluorophenyl)halogenomercuraten [{Hg(C6F5)2}3(μ‐X)]— (X = Cl,Br, I)

Structures of New Bis(pentafluorophenyl)halogeno Mercurates [{Hg(C₆F₅)₂}₃(μ‐X)]^— (X = Cl, Br, I) From the reactions of [PNP]Cl or [PPh₄]Y (Y = Br, I) with Hg(C₆F₅)₂ crystals of the composition [Cat][{Hg(C₆F₅)₂}₃X] (Cat = PNP, X = Cl ( 1 ); Cat = PPh₄, X = Br ( 2 ), I ( 3 )) are formed. 1 crystallizes in the triclinic space group P1¯, 2 and 3 crystallize isotypically in the monoclinic space group C2/c. In the crystals the halide anions are surrounded by three Hg(C₆F₅)₂ molecules. The reaction of [PPh₄]Br with Hg(C₆F₅)₂ under slightly changed conditions gives the compound [PPh₄]₂[{Hg(C₆F₅)₂}₃(μ‐Br)][{Hg(C₆F₅)₂}₂(μ‐Br)] ( 4 ).     

Complexation of Anions Including Nucleotide Anions by Open‐Chain Host Compounds with Amide,Urea, and Aryl Functions

A systematical evaluation of association constants between halide, phosphate, and carboxylate anions with N‐methylformamide ( 1 ) and the related bidentate receptors 2 – 6 (derived from, e.g., phthalic acid or ethylenediamine) in CDCl₃ as solvent yielded increments of complexation free‐energy ΔΔG for each single H‐bond, which varied like, e.g., 5.1 kJ/mol (for Cl⁻), 4.0 kJ/mol (for Br⁻), 4.0 kJ/mol (for I⁻) (with values taken from Tables 1 and 2), in line with expected H‐bond strength. The observed complexation induced NH‐NMR shift (CIS) values also showed a regular change, in the case of 1 , e.g., from 5.0 to 2.8 to 2.1 ppm (Table 1), with about half of these values with the bidentate ligands (Tables 2 and 3). Tridentate hosts led to a substantial binding increase, if strain‐free convergence of all NH donor functions towards the anion was possible. The tris[urea] ligand 10 yielded, even in the polar solvent DMSO, with Cl⁻ a ΔG of −21.5 kJ/mol and with Br⁻ of −10⋅5 kJ/mol, whereas with I⁻, no association was detectable. The results demonstrated that small, inexpensive, and conformationally mobile host compounds can exhibit high affinities as well as descrimination with anions, as much as more preorganized receptors do which require multistep synthesis. The corresponding adamantyl derivative 13 allowed measurements also in CDCl₃, with K=4.3⋅10⁴ M ⁻¹ for chloride (Table 7). Complexes with nucleotide anions were again particularly strong with the tridentate urea‐based ligands, the latter being optimal ligands for chloride complexation. For the association of 10 with AMP²⁻ and GMP²⁻in (D₆)DMSO, the association constants were 3⋅10⁴ M ⁻¹ (Table 8) and almost the same as with Cl⁻. In the case of the urea derivatives 17 , 18 , and 21 , containing only one phenyl or pyrenyl substituent, however, the ΔG values decreased in the order A>C>T>G (e.g. −13.6, −11.6, −7.6, −10.5 kJ/mol in the case of 17 , resp.; Table 8). In H₂O, the pyrenyl‐substituted urea derivatives allow measurements with fluorescence, and, unexpectedly, show only smaller nucleobase discrimination, with constants around 3⋅10³ M ⁻¹.     

Diverse Reactivity of bis(Silylene) and bis(Germylene) [LE−EL (E=Si and Ge: L=PhC(NtBu)2)] in the Oxidative Activation of C−F Bond: Si−Si Bond is Retained While the Ge−Ge Bond Is Cleaved

Herein we report the reactions of 3,4,5,6-tetrafluoroterephthalonitrile ( 1 ) with bis(silylene) and bis(germylene) LE−EL [E=Si ( 2 ) and Ge( 3 ): L=PhC(N^tBu)₂)]. The reaction of LSi−SiL (L=PhC(N^tBu)₂) ( 2 ) with two equivalents of 1 resulted in an unprecedented oxidative addition of a C−F bond of 1 leading to disilicon(III) fluoride {L(4-C₈F₃N)FSi−SiF(4-C₈F₃N)L}( 4 ), wherein the Si−Si single bond was retained. In contrast, the reaction of LGe−GeL (L=PhC(N^tBu)₂) ( 3 ) with one equivalent of 1 resulted in the oxidative cleavage of Ge−Ge bond leading to L(4-C₈F₃N₂)Ge ( 5 ) and LGeF ( 6 ). All three compounds ( 4 – 6 ) were characterized by NMR spectroscopy, EI-MS spectrometry, and elemental analysis. X-ray single-crystal structure determination of compound 4 unequivocally established that the Si^III−Si^III bond remains uncleaved.     

Theoretical Comparison of the Bonding in CpCr(CO)2(NX) [X = O,S, Se,Te]

Molecular orbital calculations employing the PM3 model have been used to examine the bonding in the complexes CpCr(CO)₂(NX) (X = O, S, Se, Te). The previously established trend of increasing Cr-N interaction as X changes from O to S is demonstrated by these calculations, and found to extend to Se and Te. Bond lengths, bond orders, vibrational frequencies, and heats of reaction are used to support the conclusion that metal to ligand π-backbonding increases down the periodic chart from NO to NTe.     

Photochemistry with Chlorine Trifluoride: Syntheses and Characterization of Difluorooxychloronium(V) Hexafluorido(non)metallates(V), [ClOF2][MF6] (M=V,Nb, Ta,Ru, Os,Ir, P,Sb)

A photochemical route to salts consisting of difluorooxychloronium(V) cations, [ClOF₂]⁺, and hexafluorido(non)metallate(V) anions, [MF₆]⁻ (M=V, Nb, Ta, Ru, Os, Ir, P, Sb) is presented. As starting materials, either metals, oxygen and ClF₃ or oxides and ClF₃ are used. The prepared compounds were characterized by single-crystal X-ray diffraction and Raman spectroscopy. The crystal structures of [ClOF₂][MF₆] (M=V, Ru, Os, Ir, P, Sb) are layer structures that are isotypic with the previously reported compound [ClOF₂][AsF₆], whereas for M=Nb and Ta, similar crystal structures with a different stacking variant of the layers are observed. Additionally, partial or full O/F disorder within the [ClOF₂]⁺ cations of the Nb and Ta compounds occurs. In all compounds reported here, a trigonal pyramidal [ClOF₂]⁺ cation with three additional Cl⋅⋅⋅F contacts to neighboring [MF₆]⁻ anions is observed, resulting in a pseudo-octahedral coordination sphere around the Cl atom. The Cl−F and Cl−O bond lengths of the [ClOF₂]⁺ cations seem to correlate with the effective ionic radii of the M^V ions. Quantum-chemical, solid-state calculations well reproduce the experimental Raman spectra and show, as do quantum-chemical gas phase calculations, that the secondary Cl⋅⋅⋅F interactions are ionic in nature. However, both solid-state and gas-phase quantum-chemical calculations fail to reproduce the increases in the Cl−O bond lengths with increasing effective ionic radius of M in [MF₆]⁻ and the Cl−O Raman shifts also do not generally follow this trend.     

Selenoarsenate aus wäßriger Lösung. Die Kristallstruktur von Na3AsO3Se · 12 H2O und Na3AsSe4 · 9H2O

Selenoarsenates from Aqueous Solutions. Crystal Structures of Na₃AsO₃Se · 12 H₂O and Na₃AsSe₄ · 9 H₂O Selenoarsenates are obtained from aqueous solutions as colourless hydrated salts by reactions either of As₂O₃ with NaOH and selenium or of Na₂Se with As₂Se₃ and selenium under strictly anaerobic conditions. Besides of tetrahedral anions AsO₃Se³⁻ and AsSe₄³⁻, extensive hydrogen bridge systems with rather strong O H …︁s Se bonds determine the structures. Na₃AsO₃Se · 12 H₂O is orthorhombic (P2₁2₁2₁) with a = 9.220(3), b = 13.018(3), c = 14.048(4) Å, Z = 4. Cubic Na₃AsSe₄ ·s 9H₂O (P2₁3) with a = 12.149(3) Å is isotypic to Schlippe's salt, Na₃SbS₄ · 9 H₂O. The full X-ray structure analyses from four-circle diffractometer data show the selenium atoms of the AsO₃Se³⁻ and AsSe₄³⁻ anions to be H-acceptors in six Se …︁ H O hydrogen bridges with d(Se …︁ O) = 3.357–3.693 Å and d(Se …︁ H) = 2.47–2.89 Å. The As Se bond in AsO₃Se³⁻ (2.283 Å) is shorter than in AsSe₄³⁻ (2.319 Å).     

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 [Cr₂O₂F₉]⁻ 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.     

Conformational analysis of X3PNP(O)X2 and (X3PNPX3)+ for X = H,F, Cl,CH3 by the pcilo method

Conformational energy maps have been calculated, using the PCILO method, for X₃PNP(O)X₂ and (X₃PNPX₃)⁺ for X = H, F, Cl, CH₃ as a function of the PNP angle. In H₃PNP(O)H₂ the global energy minimum corresponds to the eclipsed conformation of the H₃P and P(O)H₂ fragments for all PNP angles, while in Cl₃PNP(O)Cl₂, the global minimum always has Cl₃P and P(O)C1₂ staggered: the global minimum in F₃PNP(O)F₂ corresponds to eclipsed F₃P and P(O)F₂ fragments at low PNP angles and staggered fragments at high PNP angles: in (CH₃))₃PNPO(CH₃)₂ the global minimum conformation is very sensitive to ∠ PNP. Subordinate energy minima occur for all X₃PNP(O)X₂, species: in particular, there are two local conformational minima for Cl₃PNP(O)Cl₂ at the optimum value of ∠ PNP, and the relative energies of the three stable conformations are in good agreement with those derivable from the ³¹P NMR spectrum of this compound. In (X₃PNPX₃)⁺ the global minimum, usually the sole minimum on the conformational energy surface, is always close to the eclipsed conformation: free rotation of the X₃P groups relative to one another is approached in each (X₃PNPX₃)⁺ ion as ∠PNP approaches 180°. The conformations of the transition states for the equilibria between energy minima are reported with their relative energies, for X₃PNP(O)X₂ (X = H, F. Cl, CH₃) and for (Cl₃PNPCl₃)⁺     

Saturated N-Heterocyclic Carbene Based Thiele's Hydrocarbon with a Tetrafluorophenylene Linker

The synthesis of a SIPr [1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene] derived Kekulé diradicaloid with a tetrafluorophenylene spacer ( 3 ) has been described. Two synthetic routes have been reported to access 3 . The cleavage of C−F bond of C₆F₆ by SIPr in the presence of BF₃ led to double C−F activated compound with two tetrafluoro borate counter anions ( 2 ), which upon reduction by lithium metal afforded 3 . Alternatively, 3 can be directly accessed in one step by reacting SIPr with C₆F₆ in presence of Mg metal. Compounds 2 and 3 were well characterized spectroscopically and by single-crystal X-ray diffraction studies. Experimental and computational studies support the cumulenic closed-shell singlet state of 3 with a singlet-triplet energy gap (ΔE_S–T) of 23.7 kcal mol⁻¹.     

Silicophosphates of Rhodium and Indium

Single crystals of Rh(Si₂O)(PO₄)₃ and In₄(Si₂O) · (PO₄)₆ were prepared by chemical transport reactions in silica tubes and their structures were determined. Crystal data of Rh(Si₂O)(PO₄)₃: trigonal, space group P 3 c1, a = 8.088(3) Å, c = 8.740(2) Å, Z = 2, R(F²) = 0.0379, R_w(F²) = 0.0518 for 601 unique reflections. In₄(Si₂O)(PO₄)₆: hexagonal, space group P6₃/m, a = 8.5149(10) Å, c = 7.7481(12) Å, Z = 1, R(F²) = 0.0436, R_w(F²) = 0.0522 for 509 unique reflections. Both of the compounds have hexagonal close packed array of phosphate groups with metal atoms and SiOSi units in the octahedral interstices, where the SiOSi units show occupational disorder. The structure of the indium compound is considered to be a disordered structure of the reported Mo₄Si₂P₆O₁₃ structure, and contains confacial bioctahedral units.     

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag+/X2 (X=Cl,Br, I) System

The synergistic Ag⁺/X₂ system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X₂ or Ag⁺ alone. Intermediates for its action may include [Ag_m(X₂)_n]^m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I₂‐Ag( A ), [Ag₂(I₂)₄]²⁺( A ^?)₂ and [Ag₂(I₂)₆]²⁺( A ^?)₂?(I₂)_x≈0.65 form by reaction of Ag( A ) ( A =Al(OR^F)₄; R^F=C(CF₃)₃) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I₂‐Ag( A ) is ideally set up to act as a 2 e^? oxidant with stoichiometric formation of 2 AgI and 2 A ^?. Preliminary reactivity tests proved this ( A )Ag‐I₂‐Ag( A ) starting material to oxidize n‐C₅H₁₂, C₃H₈, CH₂Cl₂, P₄ or S₈ at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF₆ (M=4d metals). This suggests that ( A )Ag‐I₂‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.     

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag+/X2 (X=Cl,Br, I) System

The synergistic Ag⁺/X₂ system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X₂ or Ag⁺ alone. Intermediates for its action may include [Ag_m(X₂)_n]^m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I₂‐Ag( A ), [Ag₂(I₂)₄]²⁺( A ⁻)₂ and [Ag₂(I₂)₆]²⁺( A ⁻)₂⋅(I₂)_x≈0.65 form by reaction of Ag( A ) ( A =Al(OR^F)₄; R^F=C(CF₃)₃) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I₂‐Ag( A ) is ideally set up to act as a 2 e⁻ oxidant with stoichiometric formation of 2 AgI and 2 A ⁻. Preliminary reactivity tests proved this ( A )Ag‐I₂‐Ag( A ) starting material to oxidize n‐C₅H₁₂, C₃H₈, CH₂Cl₂, P₄ or S₈ at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF₆ (M=4d metals). This suggests that ( A )Ag‐I₂‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.     

Theoretical study of polyoxide clusters Sc20O30, P20O50, Ti20O30F20, and V20O30F20

The structural, electronic, and vibrational characteristics and energies of the isolated polyoxide clusters Sc₂₀O₃₀, P₂₀O₅₀, Ti₂₀O₃₀F₂₀, and V₂₀O₃₀F₂₀ and ammonia complexes Sc₂₀O₃₀ · nNH₃ were calculated by the density functional theory B3LYP method with several basis sets. The computation results show that a fullerene-like closo structure I _h with oxygen bridges located above the midpoints of the edges of an empty [M₂₀] dodecahedron is preferable for the Ti₂₀O₃₀F₂₀ and V₂₀O₃₀F₂₀ clusters with four-coordinate metal atoms protected by the outer M-F bonds. This structure with a cage diameter of ∼1 nm and the diameter of nearly planar decagonal faces (windows) of ∼0.5 nm is stable to dissociation into fragments and to strong geometric distortions and retains its closo shape when molecules like NH₃ and anions like H⁻ are attached to the cage. An analogous closo structure is favorable for the P₂₀O₅₀ cluster; however, in this structure, the [P₂₀] cage is severely distorted and all 12 windows are strongly corrugated. For Sc₂₀O₃₀, the I _h dodecahedron with bare three-coordinate Sc atoms corresponds to a local minimum of the potential energy surface, which is 170–200 kcal/mol less favorable than compact puck-shaped isomers in which four- and five-coordinate metal atoms and three- and four-coordinate oxygen atom prevail. “Solvation” of the dodecahedral and puck-shaped Sc₂₀O₃₀ isomers by ammonia molecules strongly decreases the energy gap between the isomers; however, the dodecahedron I _h in all cases remains a high-lying intermediate. According to calculations, most polyoxides under consideration have a high electron affinity (comparable with or higher than that of fullerenes) and is able to add three to five or more alkali-metal atoms to form radical salts in which clusters are in the state of polyanions. Because of large sizes of the [M₂₀] cages and their windows, the interior of the cage (as distinct from fullerenes) can accommodate a considerable number of atoms and several small molecules. The V₂₀O₃₀F₂₀ cluster has 20 unpaired electrons and can be treated as a molecular magnet. The properties of the [M₂₀] cages depend only slightly on the outer substituents. It is suggested that the pattern will be retained upon the substitution of OH groups for the F atoms and that the hydroxo-substituted clusters can bind to each other through hydrogen bridges and serve as building blocks for self-assembly into ordered nanometer and crystalline structures of various dimensions. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 5, pp. 775–785.