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1.
M4X3[Si2O7]-Type Lanthanide Chalcogenide Disilicates (M ? Ce? Er; X ? S, Se) Attempts to produce single crystals of MSe2 (or MSe2?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 (X2?) and disilicate anions ([Si2O7]6?). (M1)3+ is surrounded by eight (five X2? and three terminal O2? of the disilicate group), (M2)3+ by nine (three X2? and six terminal O2? 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°).  相似文献   

2.
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.  相似文献   

3.
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.  相似文献   

4.
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 = ZnII, MnII, FeIII, CoII) leading to the M2X2W20‐type heteropolytungstates.  相似文献   

5.
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  相似文献   

6.
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.  相似文献   

7.
8.
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 ).  相似文献   

9.
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.  相似文献   

10.
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(NtBu)2)]. The reaction of LSi−SiL (L=PhC(NtBu)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(NtBu)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 SiIII−SiIII bond remains uncleaved.  相似文献   

11.

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.  相似文献   

12.
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 MV 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.  相似文献   

13.
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).  相似文献   

14.
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 Ft−Ng−Fb- - -Cr(O)F4 structural units in which NgF2 is weakly coordinated to CrOF4 by means of a fluorine bridge, Fb, in which Ng−Fb is elongated relative to the terminal Ng−Ft bond. In contrast with XeF2 ⋅ 2MOF4 (M=Mo or W) and KrF2 ⋅ 2MoOF4, in which the Lewis acidic, F4(O)M- - -Fb- - -M(O)F3 moiety coordinates to Ng through a single M- - -Fb−Ng bridge, both fluorine ligands of NgF2 coordinate to CrOF4 molecules to form F4(O)Cr- - -Fb−Ng−Fb- - -Cr(O)F4 adducts in which both Ng−Fb bonds are only marginally elongated relative to the Ng−F bonds of free NgF2. Quantum-chemical calculations show that the Cr−Fb bonds of NgF2 ⋅ CrOF4 and NgF2 ⋅ 2CrOF4 are predominantly electrostatic with a small degree of covalent character that accounts for their nonlinear Cr- - -Fb−Ng bridge angles and staggered O−Cr- - -Fb−Ng−Ft 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.  相似文献   

15.
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)+  相似文献   

16.
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 (ΔES–T) of 23.7 kcal mol−1.  相似文献   

17.
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, Rw(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, Rw(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.  相似文献   

18.
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 [Agm(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(ORF)4; RF=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.  相似文献   

19.
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.  相似文献   

20.
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 [Agm(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(ORF)4; RF=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.  相似文献   

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