(SiH)48X12 Heterofullerenes with the Group III and V Dopants: A DFT Prediction of Geometry,Stability, and Electronic Structure

We have applied DFT calculations to devise some (SiH)₄₈X₁₂ heterofullerenes with replacing of 12 Si–H units with a series of the group III and V dopants, P, N, As, B, Al and Ga, with the configuration of one dopant per pentagonal ring. Our results indicate that binding energies of heterofullerenes with group III dopants are smaller than those of heterfullerenes with group V dopants. Density of state obtained for the systems indicate a distinct change near the valence level compared to that of Si₆₀H₆₀, and a local energy level appears after the doping. (SiH)₄₈X₁₂ heterofullerenes with the group III and V dopants are composed of positively and negatively charged dopant atoms, each of which is surrounded by opposite charged Si atoms. The electrophilicity values of (SiH)₄₈X₁₂ heterofullerenes, except for (SiH)₄₈N₁₂, are greater than that of their parent. Because of the higher electronegativity of group V elements and electron transfer from the cages to the group V dopants, electrophilicity values for the (SiH)₄₈X₁₂ heterofullerenes with the group V dopants are always smaller than those of heterofullerenes with the group III dopants.     

Is dodecahedral P20 special?

Summary The laboratory study of phosphorus clusters by laser-based mass spectrometric methods indicates, tentatively, that P ₊ ²¹ may be special. A plausible interpretation might place a P⁺ ion interior to a dodecahedral P₂₀ molecule.Ab initio quantum mechanical methods have been applied to the P₂₀ molecule using contracted gaussian basis sets as large as (9s 6p 4d 3f) on each phosphorus atom. At the highest level of theory, dodecahedral P₂₀ is predicted to lie 23 kcal/mol above five separated P₄ molecules.Dedicated to Professor Werner Kutzelnigg     

不同硅铝比Cu-ZSM-5纳米片上N2O催化分解

以双季铵盐表面活性剂为模板剂,水热条件下合成了硅铝比(nSi/nAl)为18、26和95的ZSM-5沸石纳米片,采用离子交换方法制备了铜改性的ZSM-5纳米片样品,并测试了其催化分解N_2O性能。结合X射线衍射(XRD)、N_2吸附/脱附、X射线荧光光谱(XRF)、扫描电镜(SEM)、透射电镜(TEM)、氢气程序升温还原(H_2-TPR)、氧气程序升温脱附(O_2-TPD)和原位红外漫反射光谱(CODRIFT)等表征结果 ,探讨了沸石硅铝比对于催化剂N_2O分解性能的影响及其原因。结果表明,ZSM-5纳米片硅铝比越低,CuZSM-5纳米片催化剂的活性越高。催化活性的提高归因于低硅铝比催化剂上Cu~+活性物种可还原性的增强和吸附氧脱附能力的提高。     

üBER DIE INSERTION VON RPS2 IN DIE PN-BINDUNG VON AMINOPHOSPHINEN

Abstract

Aminophosphine des Typs R_n P(NR′₂)_3-n (n= 2, 1, 0; R = Ph, c-Hex, (-)Men, t-Bu; R′= Me, Et, n-Bu) reagieren mit 2, 4-Bis(aryl)-1, 3, 2, 4-dithiadiphosphetan-2, 4-disulfiden (ArPS₂)₂(Ar: Ph, 4-Methoxyphenyl = An, Naphthyl, Thienyl) unter formaler Insertion monomerer {ArPS₂)-Einheiten in eine oder in zwei der λ³-P—N-Bindung zu chiralen Organophosphorverbindungen Ar(R′₂N)P(S)—S—PR_n (NR′₂)_2-n(n = 2, 1, 0) und [Ar(R′₂N)P(S)—]₂PR₂(NR′₂)_1-n (n = 1.0). In diesen werden bei Raumtemperatur bevorzugt die λ³—P—N—und λ³—P—S-Bindungen durch H₂O oder Methanol unter Bildung von Produktgemischen solvolysiert. Mit Chlorwasserstoff bildet sich aus An(Et₂N)P(S)—S—PPh(NEt₂) das An(Et₂ N)P(S)—S—PPh(C1). Addition von Schwefel führt zu Ar(R′₂N)P(S)—S—P(S)R_n (NR′)_2-n (n=2, 1). Die Stereoisomerenbildung der neuen Verbindungen wird besprochen und ihre Struktur sowie die Zusammensetzung der Reaktionsmischungen aus den ³¹P-Spektren hergeleitet.

Aminophosphines R_n P(NR′₂)_3-n (n = 2, 1, 0; R = Ph. c-Hex, (-)Men, t-Bu; R′= Me, Et, n-Bu) react with 2, 4-Bis(aryl)-1, 3, 2, 4-dithiadiphosphetane-2, 4-disulfides (ArPS₂)₂ (Ar: Ph, 4-Methoxyphenyl = An, Naphthyl, Thienyl) under formal insertion of monomeric {ArPS₂)-units in one or in two of the λ³-P—N-bonds to yield chiral organophosphorus compounds Ar(R′₂N)P(S)—S—]₂PR_n (NR′₂)₂ (n = 2, 1, 0) and [Ar(R′₂N)P(S)—S—]₂ PR₂ (NR′₂)_2-n (n = 1, 0). At room temperature chiefly the A—P—N and A³—P—S-bonds in these products are solvolyzed by H, O or methanol with formation of mixtures of compounds. With hydrogen chloride An(Et₂N)P(S)—S—PPh(NEt₂) is converted into An(Et₂N)P(S)—S—PPh(Cl). Addition of sulfur yields Ar(R′₂N)P(S)—S P(S)R_n (NR′₂)_2-n (n = 2, 1). Stereoisomerism of the new compounds is discussed and their structures as well as the composition of reaction mixtures are deduced from “P-NMR-spectra”.     

Ditopic complexes of silene H2SiCH2 with bidentate ligands Me2NCH2SiHnF3-n. Structures, formation energies, AIM and ELF analyses.

Ditopic complex formation of silene H₂SiCH₂ with bidentate ligands Me₂NCH₂SiH_nF_3-n (n = 0-3) was studied at the MP4(SDQ(T)6-311G(d,p))//MP2/6-31G(d,p) levels of theory. The AIM and ELF analyses have shown that π-bonding in the silenic Si¹C moiety in the relatively weak (H₂Si¹CH₂)·(Me₂NCH₂Si²H_nF_3-n) (n = 2, 3) ditopic complexes is partially preserved.     

A SEM/EDXA study on the chemical attack of aqueous NaOH/KOH solutions on the surface of the metal-metalloid glass (Fe, Cr)80 (P, C, Si)20 and Fe75Cr5P8C10Si2, respectively

After a treatment of the metal-metalloid glassy alloy (Fe, Cr)₈₀ (P, C, Si)₂₀ and Fe₇₅Cr₅P₈C₁₀Si₂, respectively, by aqueous alkaline solutions of 1.0M NaOH + 1.0M KOH and 2.5M NaOH + 2.5M KOH, respectively, a SEM/EDXA study of the glass surface was performed.The results of the accelerated ageing procedure demonstrate that the glass treated with the 1.0M NaOH + 1.0M KOH solution at room temperature (20 °C) is characterized by a surface state like that of the initial material.For the glass treatment with the 2.5M NaOH + 2.5M KOH solution at 20 °C the surface layer shows a different morphology and is thicker. It can be supposed that the reinforcing property is reduced.The glass treatment at 80 °C with the aqueous solutions 1.0M and 2.5M (NaOH + KOH), respectively, leads to surface layers of different morphology and such a layer is about 5 m thick. The strength of solid residue of such a treated glass is very low.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Theoretical Study on Inverse Sandwich Complexes [E-C{5-n}H{5-n}Nn-E]+ and [E-C{5-n}H{5-n}Pn-E]+ (n=1, 2, 3; E=Al,Ga, In,Tl)

The inverse sandwiches [E-C_{5-n}H_{5-n}N_n-E]⁺ and [E-C_{5-n}H_{5-n}P_n-E]⁺ (n=1, 2, 3; E=Al, Ga, In, Tl) with low-valent boron group elements are studied. The (η5,η5) coordinated inverse sandwich [E-C_{5-n}H_{5-n}N_n-E]⁺ is unstable in energy or nonexistent. However, the (η5,η5) coordinated [E-C_{5-n}H_{5-n}P_n-E]⁺ is not only stable in energy, but also stable against dissociation. The dissoction stability [E-C_{5-n}H_{5-n}P_n-E]⁺ with the same E element decreases as the number n increases, while for the certain n number, the dissociation energies with different E elements are close to each other. [E-C₄H₄P-E]⁺ has similar dissocition stability to the well-known [E-C₅H₅-E]⁺. The inteaction between C_{5-n}H_{5-n}P_n and lowvalent E element is mainly ionic. Since lone pairs of electrons locate on both E and P atoms, the (η5, η5) coordinated inverse sandwich [E-C_{5-n}H_{5-n}P_n-E]⁺ would act as multi electron-donors.     

Solvent-Free,Cross-Aldol Condensation Reaction Using Silica-Supported,Phosphorus-Containing Reagents Leading to α,α′-Bis(arylidene)cycloalkanones

This article describes an efficient, simple, and clean method for the synthesis of α,α′-bis(arylidene, furylidene and cinnamylidene)cycloalkanones under solvent-free conditions. The cross-aldol condensation of cycloalkanones with aldehydes in the presence of silica-supported phosphorus pentoxide (P₂O₅/SiO₂) or silicaphosphinoxide (silphox, [POCl_3-n(SiO₂)_n]) as heterogeneous reagents produces the title compounds in good to excellent yields.     

Effect of intercalation of metal ions on the colloidal and solid properties of vanadium pentaoxide hydrate,V2O5 nH2O

The colloidal stability of V₂O₅ nH₂O was studied on the basis of the measurements of critical flocculation concentration (CFC) by metal ions, amount of ions exchanged (or intercalated), and -potential. In total, the CFC values obeyed the Schulze Hardy law and strong Hofmeister's series was found in the systems including alkaline ions. The sequence of colloidal stability of V₂O₅ nH₂O in the electrolyte solutions was related to the intercalation of metal ions in the interlayer spaces of the solid. The largest CFC value for Li⁺ (87 mmol dm^–3) was explained by smaller affinity of Li⁺ to be intercalated in V₂O₅ nH₂O as well as smaller Hamaker constant of the intercalated solid compared to the other systems.Effect of intercalation of metal ions on the crystalline properties of the materials was measured by use of XRD and electron microscope. Under highly dehydrated condition the ions whose radii are smaller than 0.1 nm are captured in the structure of V₂O₅ nH₂O without changing interlayer distances, while those larger than 0.1 nm increase the interlayer distance. In a saturated H₂O vapor interlayer distances increased with increasing charge of intercalated ions. However, when intercalated with ions carrying the same valency the interlayer distances of the sample decreased with decrease in the hydration property of ions. Hydrolyzable Cr³⁺ gave exceptionally larger interlayer distances, both in a vacuum and in H₂O vapor.     

Oligomers of C<Subscript>20</Subscript>H<Subscript>8</Subscript> polyhedral molecule: a computer simulation

DFT-PBE/DZ calculations of oligomers of C₂₀H₈ polyhedral molecule (derivative of C₂₀ fullerene) were carried out. From the results obtained it follows that quasi-one-dimensional, quasi-two-dimensional, and three-dimensional polymers with compositions [C₂₀H₈]_n can exist. The geometric parameters of the repeating units of these polymers were estimated.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1813–1817, September, 2004.     

Low-temperature heat capacities and thermodynamic properties of rare-earth triisothiocyanate hydrates (III) —Sm(NCS)3 · 6H2O, Gd(NCS)3 · 6H20, Yb(NCS)3 · 6H20 and Y(NCS)3 · 6H20

The heat capacities of four RE isothiocyanate hydrates, Sm(NCS)₃, · 6H₂0, Gd(NCS)₃ · 6H₂0, Yb(NCS)₃, · 6H₂O and Y(NCS)₃, · 6H₂0, have been measured from 13 to 300 K with a fully-automated adiabatic calorimeter. No obvious thermal anomaly was observed for the above-mentioned compounds in the experimental temperature ranges. The polynomial equations for calculating the heat capacities of the four compounds in the range of 13–300 K were obtained by the least-squares fitting based on the experimentalC _P, data. TheC _P, values below 13 K were estimated by using the Debye-Einstein heat capacity functions. The standard molar thermodynamic functions were calculated from 0 to 300 K. Gibbs energies of formation were also calculated. Project supported by the National Natural Science Foundation of China.     

Ab Initio study of the structure and vibrational spectra of ZrF n 4-n systems

The optimal geometry and vibrational spectra of a series of [ZrF_n]^4-n clusters (n = 4–8) are calculated in a nonrelativistic approximation of the Hartree-Fock-Roothaan method. The calculated frequencies of the totally symmetric stretching vibrations v_s are in satisfactory agreement with the experimental data. The values of v_s are very sensitive to minor changes in cluster geometry and to the outerspheric environment. The high stability of the [ZrF₆]²⁻ ion was confirmed in an MP2 calculation.     

Topological and thermodynamic investigations of binary mixtures: Molar excess volumes, molar excess enthalpies and isentropic compressibility changes of mixing

Molar excess volumes, V^E, molar excess enthalpies, H^E, and speeds of sound, u, of o-toluidine (i) + cyclohexane or n-hexane or n-heptane (j) binary mixtures have been determined over entire range of composition at 308.15 K. Speeds of sound data have been utilized to predict isentropic compressibility changes of mixing, of (i + j) mixtures. The observed V^E, H^E and data have been analyzed in terms of Graph theory. The analysis of V^E data by Graph theory reveals that o-toluidine exists as an associated molecular entity and (i + j) mixtures contain 1:1 molecular complex. It has been observed that V^E, H^E and values calculated by Graph theory compare well with their corresponding experimental values. The observed data have also been analyzed in term of Flory theory.     

Bildung siliciumorganischer Verbindungen. 111. Die Hydrierung Si-chlorierter,C-spiroverbrückter 2,4-Disilacyclobutane mit LiAlH4 und iBu2AlH. Der Zugang zum Si8C3H20

Formation of Organosilicon Compounds. 111. The Hydrogenation of Si-chlorinated, C-spiro-linked 2,4-Disilacyclobutanes with LiAlH₄ or iBu₂AlH. The Access to Si₈C₃H₂₀ The hydrogenation of Si-chlorinated, C-spiro-linked 2,4-disilacyclobutanes containing C(SiCl₃)₂ terminal groups with LiAlH₄ in Et₂O proceeds under complete cleavage of the fourmembered rings and under elimination of one SiH₃ group. Such, Si₈C₃Cl₂₀ 4 forms (H₃Si)₂CH? SiH₂? CH(SiH₃)? SiH₂? CH(SiH₃)₂ 4 α, and even Si₈C₃H₂₀ 4a with LiAlH₄ forms 4 α. The hydrogenation of related compounds containing however CH(SiCl₃) terminal groups similarly proceeds under ring cleavage but no SiH₃ groups are eliminated. Such, (Cl₃Si)CH(SiCl₂)₂CH(SiCl₃) 41 forms (H₃Si)₂CH? SiH₂? CH₂(SiH₃) 41 α. However, in reactions with iBu₂AlH in pentane neither the disilacyclobutane rings are cleaved nor are SiH₃ groups eliminated. Only by this method Si₈C₃H₂₀ is accessible from 4 , Si₆C₂H₁₆ 3a from Si₆C₂Cl₁₆ 3 and Si₄C₂H₁₂ 41a from 41 . C(SiCl₃)₄ cleanly produces C(SiH₃)₄. Based on the knowledge about the different properties of LiAlH₄ and iBu₂AlH in hydrogenation reactions of disilacyclo-butanes it was possible to elucidate the composition and the structures of the hydrogenated derivatives of the product mixture from the reaction of MeCl₂Si? CCl₂? SiCl₃ with Si(Cu) [1] and to trace them back to the initially formed Si chlorinated disilacyclobutanes Si₆C₂Cl₁₅Me 34 , Si₆C₂Cl₁₄Me₂ 35 , Si₈C₃Cl₁₉Me 36 and Si₈C₃Cl₁₈Me₂ 37 . Compound 4a forms colourless crystals of space group P1 with a = 799.7(6), b = 1263.6(12), c = 1758.7(14) pm, α = 103.33(7)°, β = 95.28(6)°, γ = 105.57(7)° and Z = 4.     

Stability of hollow spheroidal silicon clusters Sin and SinHn

The structures of Si_n and Si_nH_n fullerenes with 20 ≶n ≶60 are calculated in the MINDO/3 approximation using the Monte Carlo technique for geometry optimization. The calculations show that spheroidal silicon clusters consisting of more than 36 atoms are stable and the bond energy increases with their size. This increase is not noticed for compact clusters calculated as an alternative. For n ≥40-50, the latter have lower bond energies compared to fullerenes. The geometry optimization of the tetrahedral cluster Si₄₅ results in a structure close to spheroidal, which gains in bond energy. The addition of hydrogen atoms to small deformed fullerenes and their geometry optimization make it possible to obtain stable spheroidal structures Si_nH_n whose bond energy is greater than that of alternative compact silicon hydride clusters. When the size of spheroidal clusters Si_nH_n increases, i. e., when n > 36, the hydrogen elimination barriers decrease abruptly; the Si_nH_n diamond structure of the cluster is more advantageous when n ≥50.     

Wolfram(VI)-fluorid-pentafluorotellurate(VI): WFn(OTeF5)6-n

Tungsten(VI) Fluoride Pentafluorotellurates(VI): WF_n(OTeF₅)_6-n In WF₆ fluorine can be replaced by F₅TeO groups by means of B(OTeF₅)₃ to form WF_n(OTeF₅)_6-n. Isolation was achieved for WF₅OTeF₅ and cis-WF₄ (OTeF₅)₂. Compounds with n > 2 have been identified by ¹⁹F-nmr spectroscopy. The ligand behaviour of the F₅TeO group is compared to OMe and OPh.     

Formation of Silicon-Containing Polyoxoniobates from Hexaniobate Under High Temperature Conditions

Hydrothermal reaction of K₇H[Nb₆O₁₉]·13H₂O with Na₂SiO₃·9H₂O (220 °C, 24 h) produces a lacunary siliconiobate [Si₄Nb₁₆O₅₆]^16?, which was isolated as mixed salt NaK₈H₆[Na@Si₄Nb₁₆O₅₆]·26H₂O (1). Changing the silicon source to Ph₂Si(OH)₂ under the same conditions slightly improves the yield of [Si₄Nb₁₆O₅₆]^16?, which was isolated as K₁₄H[K@Si₄Nb₁₆O₅₆]·26H₂O (2). Extending the reaction time leads to rearrangement of [Si₄Nb₁₆O₅₆]^16? into Keggin-type silicododecaniobate [SiNb₁₂O₄₀]^16?, which was isolated and characterized as K₈H₂(Nb₂O₂)[SiNb₁₂O₄₀]·20H₂O (3). The complexes were characterized by X-ray single crystal analysis, elemental analysis, thermogravimetry, ²⁹Si NMR.     

Structure,spectroscopic, and magnetic properties of a new cobalt(II) complex with 5-sulfoisophthalic anion

A complex of [Co(H₂SIP)(Phen)(H₂O)₃] ? H₂O (H₂SIP = 5-sulfoisophthalic anion, Phen = 1,10-phenanthroline) has been synthesized by hydrothermal reaction. Crystal structure determination revealed that the complex crystallizes in the monoclinic space group P2(1)/c, in which Co(II) is distorted octahedral coordinating with one carboxylate sulfonate ligand, one phen, and three coordinated waters. Molecules of [Co(H₂SIP)(Phen)(H₂O)₃] ? H₂O are connected to form a 3-D structure by intermolecular hydrogen bonds and π–π stacking interactions. IR spectra, UV-Vis spectra, and magnetic susceptibilities have been analyzed to obtain values of the ligand field and magnetic parameters: Α = 1.33, λ = ?102.3 cm^?1, κ = 0.96, and Δ = 252.2 cm^?1.     

Fluorescence and phosphorescence properties of the low temperature forms of the MAl2Si2O8:Eu (M=Ca, Sr, Ba) compounds

The fluorescence and phosphorescence properties of Europium-doped MAl₂Si₂O₈ (M=Ca, Sr, Ba) are reinvestigated and discussed on the basis of the propensity of an activator to agglomerate with an oxygen vacancy. Due to a stronger attraction of the anion vacancy towards Eu²⁺ cations going from BaAl₂Si₂O₈ to SrAl₂Si₂O₈ and CaAl₂Si₂O₈ host lattices, the interpretation of the fluorescence spectra turns out to be less trivial in the Ca and Sr host lattices than in the Ba one and requests the account for Eu²⁺ cations lying at alkaline-earth sites with or without vacancy in their neighborhood. Phosphorescence in these compounds is highlighted.