Electron interactions in the closo-carboranes 1,2- and 1,7-C2B10H12

Ultra-soft X-ray fluorescence spectra of ortho- and meta-carborane C₂B₁₀H₁₂ were obtained. Ab initio self-consistent field (SCF) quantum-chemical calculations of these molecules were performed to interpret BK and CK spectra. Distinctions between electronic structure of closo-carboranes 1,2- and 1,7-C₂B₁₀H₁₂ are caused by different efficiency in the interaction of carbon and boron atoms. Location of boron atom between carbon atoms leads to stronger delocalization of electron density in meta-carborane molecule. The correlation between molecular orbitals (MOs) of the anion B₁₂H₁₂²⁻ and the closo-carboranes was carried out.     

Encapsulations of La@C82 and La2@C80 inside single-walled boron nitride nanotubes

Possibility of encapsulations of metallofullerenes inside single-walled boron nitride nanotubes (BNNTs) is studied by using first-principles calculations. We find that both La@C₈₂ and La₂@C₈₀ can be exothermically encapsulated inside the (17, 0) and (14, 7) BNNTs. The minimum diameters of exothermically encapsulating both La@C₈₂ and La₂@C₈₀ inside BNNTs are predicated to be about 13.4 Å.     

[C2B10]---[B12] double cage boron compounds—a new approach to the synthesis of water-soluble boron-rich compounds for BNCT

A new approach in the synthesis of water-soluble boron-rich compounds was proposed. The closo-dodecaborate cage is used as a hydrophilic substitutent providing for the water-solubility of the molecule whereas the carborane cage can be used for attachment to biomolecules using earlier developed methods. The double-cage molecules [o-, m-, and p-CB₁₀H₁₀C(CH₂)₄OB₁₂H₁₁]²⁻ were prepared by the reaction of the tetramethylene oxonium derivative of the closo-dodecaborate anion, [B₁₂H₁₁O(CH₂)₄]⁻, with the corresponding lithiated carboranes. The compounds obtained have doubled the boron contents and could serve for the synthesis of agents for boron neutron capture therapy (BNCT).     

超临界水热极速合成异质结构H4SiW12O40/Bi2WO6光催化剂及其脱氮性能

采用超临界水热合成方式极速合成一种H_4SiW_(12)O_(40)/Bi_2WO_6光催化剂,通过X射线衍射(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、比表面积及孔隙度(BET)测定对所合成催化剂的结构和性质进行了考察,并以吡啶含量为15 mg/g的模拟油对光催化剂的脱氮效果进行评价。结果表明,该光催化剂为二维纳米片自组装成的三维球状结构,其中,H_4SiW_(12)O_(40)与Bi_2WO_6不是简单的固载关系而是在超临界水热条件下生成一种新的晶相,正是由于这种晶相的存在,使得H_4SiW_(12)O_(40)牢固固载在Bi_2WO_6光催化剂本体上的同时,对光生载流子进行了有效疏导,提升了H_4SiW_(12)O_(40)/Bi_2WO_6光催化剂的使用寿命和光催化活性。本研究针对光催化剂制备周期与晶形发育的矛盾,将超临界水热技术与光催化剂模板导向合成技术有机结合,在获得良好晶形异质结构H_4SiW_(12)O_(40)/Bi_2WO_6光催化剂的同时明显缩短了光催化剂的制备周期,从而降低了催化剂的制备成本,攻克了光催化剂工业化应用的主要矛盾,所制备的H_4SiW_(12)O_(40)/Bi_2WO_6光催化剂轻质油脱氮效率达97%以上。     

Structure and stabilities of the isomers of SiB2H4

Ab initio quantum-mechanical methods at the HF/6–31G*, MP2/6–31G* and MP2/6–31G* levels are used to study the relative stabilities of the isomers of SiB₂H₄. Isomers obtained using the analogy between trivalent boron and divalent silicon are calculated to be more stable compared to isomers where carbon is replaced by the isovalent silicon. 2π aromaticity and the preference of silicon for lower valency control the relative stabilities of SiB₂H₄ isomers.     

前驱体溶液pH值对V2O5-WO3/TiO2催化剂的低温NH3-SCR性能的影响

采用调节前驱体溶液pH值的方法制备了用于低温NH₃-SCR的V₂O₅-WO₃/TiO₂催化剂。通过XPS、Raman光谱、H₂-TPR、NH₃-TPD、NH₃-DRIFT、XRD及物理吸附等手段对催化剂进行了表征分析,并对其脱硝催化活性进行了测试。结果表明,前驱体溶液酸性的增强能够提高催化剂表面聚合态钒物种和V⁴⁺⁽³⁺⁾/V⁵⁺的比值以及表面酸性,增加活性位数量、降低反应的活化能、提高其脱硝催化性能。因此,通过提高前驱体溶液的酸性,有助于制备出脱硝活性较好的NH₃-SCR催化剂。     

Synthesis, catalytic activity and the molecular structure of (μ3-CCH3)Co3(CO)7-μ-(Ph2PCH2PPh2)

Reaction of (μ₃-CCH₃)CO₃(CO)₉ (I) with dppm (dppm = bis-(diphenylphosphino)methane) affords the cluster (μ₃-CCH₃)Co₃(CO)₇-dppm (II). The crystal and molecular structure of II have been determined at −160°C. The dppm ligand bridges one of the three metal—metal edges in the equatorial plane to give a five-membered ring, which adopts an envelope conformation.

Cluster II functions as a catalyst for the hydroformylation of 1-pentene (80 bar of H₂/CO (1/1); 110°C). The results indicate that the dppm bridging ligand stabilizes and activates the cluster for catalysis, and open the way to the synthesis of chiral clusters.     

Fe2O3/Al2O3氧载体用于甲烷化学链燃烧：负载量与制备方法的影响

以不同方法制备了系列Fe₂O₃/Al₂O₃氧载体,采用XRD、H₂-TPR、CH₄-TPR、O₂-TPD和BET等分析技术对氧载体进行了表征。研究了不同Fe₂O₃负载量氧载体的甲烷化学链燃烧性能,考察了不同制备方法对Fe₂O₃/Al₂O₃氧载体结构、反应性和产物选择性的影响。结果表明,Fe₂O₃负载量对氧载体活性及产物中CO₂选择性的影响较大,负载量较低时氧载体活性较低且引起甲烷部分氧化产物CO含量增加。制备方法亦对氧载体与甲烷的反应活性有所影响,整体上共沉淀法制备的质量分数60％Fe₂O₃/Al₂O₃氧载体具有较高的氧化活性和化学链循环稳定性。其在反应温度850℃、反应时间15 min、30次循环后甲烷转化率及产物中CO₂选择性均未见明显降低。     

噻吩在Au_(13)和Pt_(13)团簇上加氢脱硫的反应机理比较

采用密度泛函理论研究了噻吩在立方正八面体的M_(13)(M=Au、Pt)团簇上的吸附和加氢脱硫行为。结果表明,噻吩以环吸附于Au_(13)上的Hol-tri位或Pt_(13)上的Hol-quadr位时最稳定,且Pt_(13)上的吸附稳定性更高。在M_(13)催化体系中,按间接加氢脱硫机理,反应可能依顺式加氢的方式进行;其中,C-S键断裂开环所需的活化能最高,是反应的限速步骤;按直接加氢脱硫机理,HS加氢所需活化能最高,是反应的限速步骤。同时该机理总体所需活化能较间接加氢脱硫机理更低,是更为合理的脱硫机理。噻吩加氢脱硫过程中,Au_(13)体系为放热反应,而Pt_(13)体系为吸热反应,并且Au_(13)体系加氢所需活化能更低;因此,Au_(13)更有利于噻吩加氢脱硫反应的进行。     

Nido-6-metalladecaborane chemistry: Molecular structure and fluxionality of [6,6,6,6-(CO)2(PPh3)2-nido-6-WB9H13]

The molecular and crystal structure of the nido-6-tungstadecaborane [6,6,6,6-(CO)₂(PPh₃)₂-nido-6-WB₉H₁₃] (1) has been determined showing that the tungsten atom is incorporated into the 6-position of a nido 10-vertex (WB₉) cage. The tungsten atom has a seven-coordinate capped trigonal prismatic environment and is bonded to two hydrogen and three boron atoms of the {B₉H₁₃} cage, in addition to two CO groups and two PPh₃ ligands. Variable-temperature (−90°C to +50°C) ³¹P{¹H} NMR spectroscopy of 1 reveals that the exo-polyhedral ligands about the tungsten atom are fluxional with respect to PPh₃ site exchange with an activation energy (ΔG‡), at the coalescence temperature (−73°C), of <38 kJ mol⁻¹.     

A novel nonaqueous route to V2O3 and Nb2O5 nanocrystals

The reaction between transition metal alkoxides and benzyl alcohol provides a novel soft chemistry route to metal oxide nanoparticles. The method allows the preparation of nanocrystals of two important transition metal oxides, namely V₂O₃ and Nb₂O₅. Although the reaction temperatures of 200–220 °C are comparably low, the obtained particles are highly crystalline. According to TEM investigations, the V₂O₃ crystals exhibit particle sizes between 20 and 50 nm, and the Nb₂O₅ crystals display platelet-like particle shapes with sizes of 50–80 nm, without any indications of amorphous character.     

The reported ion Fe3S2(NO)5: A re-investigation

Salts reported to contain the iron-sulphur cluster nitrosyl anion Fe₃S₂(NO)₅⁻ are shown to be identical with those containing the well-known anion Fe₄S₃(NO)₇⁻.     

Theoretical studies of third-order nonlinear optical response for B12N12, B24N24 and B36N36 clusters

In this paper, we have calculated the third-order nonlinear optical polarizabilities corresponding to three optical processes: third-harmonic generation (THG), electric-field-induced second-harmonic generation (EFISHG) and degenerate four-wave mixing (DFWM) for B₁₂N₁₂, B₂₄N₂₄ and B₃₆N₃₆ clusters. The calculations have been performed by employing ab initio time-dependent density functional theory combined with sum-over-states method (SOS//TDDFT). We obtained the similar dynamic behavior of third-order NLO polarizabilities for three BN clusters. At input photon energy below 1.25 eV, the resonance enhancements of response haven't occurred. This is due to the fact that the calculated BN clusters have the large transition energy. B₂₄N₂₄ cluster has the larger transition dipole moments and the third-order polarizabilities of B₂₄N₂₄ are much larger than those of B₁₂N₁₂ and B₃₆N₃₆. We also estimate the static third-order optical susceptibility χ⁽³⁾ for BN fullerene materials from the average static third-order polarizability <γ>. The static χ⁽³⁾ of B₂₄N₂₄ fullerene materials are 1.36×10⁻¹⁴ esu for three NLO processes.     

Studies of N-heterocyclic compounds with triosmium clusters: Formation of the heterocyclic-linked dicluster compound [Os 6(μ-H)2(μ3-C6H4N3)2(CO)18]

The cluster [Os₃(CO)₁₀(MeCN)₂] reacts with indazole (C₇H₆N₂) to give two isomeric products [0s₃(μ-H)(μ-C₇H₅N₂)(CO)₁₀] in which the five-membered ring has been metallated with N-H cleavage to give an N,N-bonded isomer or with C-H cleavage to give a C,N-bonded isomer. These two isomers have very similar X-ray structures but can be clearly distinguished by ¹H NMR methods. They are shown to correspond to related clusters derived from pyrazole. Benzotriazole (C₆H₅N₃) also reacts (as shown earlier by others) to give two isomers: an N,N-bonded species [Os₃(μ-H)(μ-C₆H₄N₃)(CO)₁₀] coordinated only through the five-membered ring and a minor C,N-bonded isomer [Os₃(μ-H)(μ-C₆H₄N₃)(CO)₁₀], metallated at the C₆ ring and coordinated through both rings. The former isomer reacts with Me₃NO in acetonitrile to give [Os₃(μ-H)(μ-C₆H₄N₃)(CO)₉(MeCN)] which thermally looses MeCN to produce the coupled product [Os₆(μ-H)₂(μ₃-C₆H₄N₃)₂(CO)₁₈] which was shown by X-ray structure determination to have all six nitrogen atoms coordinated to osmium, a novel situation for coordinated benzotriazole. The two Os₃ units are linked together by an OsNNOsNN ring in a boat conformation with the whole cluster adopting C₂ symmetry.     

Hydrothermal syntheses and crystal structures of bimetallic cluster complexes [{Cd(phen)2}2V4O12]·5H2O and [Ni(phen)3]2[V4O12]·17.5H2O

The hydrothermal reactions of vanadium oxide starting materials with divalent transition metal cations in the presence of nitrogen donor chelating ligands yield the bimetallic cluster complexes with the formulae [{Cd(phen₂)₂V₄O₁₂]·5H₂O (1) and [Ni(phen)₃]₂[V₄O₁₂]·17.5H₂O (2). Crystal data: C₄₈H₅₂Cd₂N₈O₂₂V₄ (1), triclinic. a=10.3366(10), b=11.320(3), c=13.268(3) Å, =103.888(17)°, β=92.256(15)°, γ=107.444(14)°, Z=1; C₇₂H₁₃₁N₁₂Ni₂O_29.5V₄ (2), triclinic. a=12.305(3), b=13.172(6), c=15.133(4), =79.05(3)°, β=76.09(2)°, γ=74.66(3)°, Z=1. Data were collected on a Siemens P4 four-circle diffractometer at 293 K in the range 1.59° <θ<26.02° and 2.01°<θ<25.01° using the ω-scan technique, respectively. The structure of 1 consists of a [V₄O₁₂]⁴⁻ cluster covalently attached to two {Cd(phen)₂}²⁺ fragments, in which the [V₄O₁₂]⁴⁻ cluster adopts a chair-like configuration. In the structure of 2, the [V₄O₁₂]⁴⁻ cluster is isolated. And the complex formed a layer structure via hydrogen bonds between the [V₄O₁₂]⁴⁻ unit and crystallization water molecules.     

A novel arene bonding mode in the mixed-metal cluster Os4Ru(μ-H) 3(CO) 12(μ3-η-C6H5) P(OMe)3

The ionic coupling of [Os₄H₂(CO)₁₂]²⁻ with [Ru(η⁶-C₆H₆)(MeCN)₃]²⁺ affords the neutral mixed metal cluster Os₄Ru(μH)₂(CO)₁₂(η⁶-C₆H₆) 1. The reaction of 1 with trimethylphosphite leads to the initial formation of the addition product Os₄Ru(μH)₂(CO)₁₂(η⁶-C₆H₆)P(OMe)₃ 2, but this complex rearranges in solution to give Os₄Ru(μ-H)₃(CO)₁₂(μ₃-η⁶-C₆H₅)P(OMe)₃ 3. An X-ray structure of 3 shows that the metal core of the cluster is a ruthenium-spiked Os₄ tetrahedron, with one hydrogen atom from the arene having transferred to the Os₄ core, and one arene carbon bridging an Os-Os edge, while the ring as a whole remains η⁶-bound to the Ru atom.     

Synthesis, structural characterization and reactivity of the amino borane 1-(NPh2)-2-[B(C6F5)2]C6H4

The bright red title compound 1 was synthesized from (2-lithiophenyl)diphenylamine and bis(pentafluorophenyl)boron chloride. Its reactions with small acids like H₂O and HCl proceeded easily giving zwitterionic compounds. For 1 and its water adduct 2 the crystal structures were determined, the latter featuring an ammonium borate structure containing a short intramolecular hydrogen bond bridge. Treatment of 1 with Jutzi's acid, [H(OEt₂)₂][B(C₆F₅)₄], did not result in protonation of the nitrogen, but reaction of 1 with LiH in the presence of 12-crown-4, led to the isolation of the aminoborate [1-(Ph₂N)-2-{B(H)(C₆F₅)₂}C₆H₄][Li(12-crown-4)] (3). Borohydride 3 reacted with Jutzi's acid to regenerate 1 and liberate hydrogen.     

锂盐及制备工艺对固态电解质Li7La3Zr2O12成相的影响研究

石榴石型Li₇La₃Zr₂O₁₂(LLZO)离子导电性高,在全固态锂离子电池中具有潜在的应用价值。但目前报道的LLZO制备工艺烧结温度范围宽,稳定性差,不利于宏量制备。本文以烧结产物物相结构和结晶度为考察指标,系统研究了锂源及用量、烧结温度、烧结时间等因素对LLZO成相的影响。结果表明,当以分解温度较低的锂盐(LiNO₃)为原料时,在800℃下得到四方相LLZO,900℃时呈立方相LLZO;当以分解温度较高的锂盐(Li₂CO₃)为原料时,900℃才能形成四方相LLZO。烧结时间的延长和温度升高均会导致锂的挥发损失,影响LLZO物相的形成。通过增加锂盐用量、改变烧结前驱体聚集特性与烧结时间可抑制锂的挥发。当以过量10%的Li₂CO₃为原料时,900℃烧结6h可稳定的得到立方相LLZO。该研究较为系统地分析了制备工艺对LLZO成相的影响,可为LLZO宏量稳定制备提供借鉴。     

Ammonia deposition in fullerene: (NH3)n@C60

Deposition of ammonia molecules in fullerene has been investigated theoretically by performing semi-empirical molecular orbital calculation at PM3 level within RHF formalism. C₆₀ cluster has been doped endohedrally by ammonia molecules. Structural and electronic properties of the systems considered have been studied. It has been found that C₆₀ cluster can store at most six ammonia molecules. The ammoniacal endofullerenes, (NH₃)_n@C₆₀, have been found stable but endothermic.     

The coordinatively unsaturated cluster cations [Pt3{M(CO)3}(μ-Ph2PCH2PPh2)3] (M = Re, Mn)

The coordinatively unsaturated cluster [Pt₃(μ₃-CO)(μ-dppm)₃]²⁺ (1, dppm = Ph₂PCH₂PPh₂) reacts with Na⁺[M(CO)₅]⁻ to give the mixed metal clusters [Pt₃{M(CO)₃}(μ-dppm)₃]⁺ (M = Re, 2; Mn, 3). The new clusters are characterized by spectroscopic methods and, for M = Re, by an X-ray structure determination. The Pt₃Re core in 2 is tetrahedral with particularly short metal-metal distances.