The electronic structure ofα-B12, B12P2 and B12AS2

The electronic band structures of the rhombohedral-based boron compounds -B₁₂, B₁₂P₂ and B₁₂ As₂ have been investigated along all symmetry directions. The calculations show that the band gap, in all cases, is of the order of 2 eV, which correlates with the known color of -rhombohedral boron. The materials should be intrinsic semi-conductors, as has recently been shown experimentally. The states around the band gap in -B₁₂ are dominated by the boron 2p atomic states. The bonding in the icosahedra, as illuminated by cluster calculations, is shown to be rather similar to that in the isolated B₁₂ icosahedron. Of the intericosahedron interactions, those between B(2) and B(2) atoms are the strongest and have a bond index just above unity. In B₁₂P₂ the orbitals of the P₂ moiety make a significant contribution to the valence band edge states and the conduction band edge states also incorporate considerable (55%) phosphorus 3d orbital character. In B₁₂As₂ the arsenic 4d orbitals do not have as much effect in that crystal as do the 3d orbitals in B₁₂P₂.     

双电荷离子[C12H12N2O]2+和[C12H12N2S]2+的气相单分子分解反应研究

The unimolecular dissociation reactions of doubly charged ions were reported,which resulted from a tandem mass spectrometer and a reversed geometry double focusing mass spectrometer by electron impact.Mass analyzed ion kinetic energy spectrometry(MIKES) was used to obtain the kinetic energy releases in charge separation reactions of doubly charged ions.The intercharge distances between the two charges at transition states can be calculated from the kinetic energy releases.Transition structures of unimolecular dissociation reactions were infered from MIKES and MS/MS.     

Infrarotspektroskopische Untersuchung des Borcarbids und seiner isotypen Derivate B12O2, B12P2 und B12As2

Infrared Spectra of Boron Carbide and its Isotypic Derivatives B₁₂O₂, B₁₂P₂, and B₁₂As₂ From very finely powdered samples of B₄C [ = B₁₁C(CBC)], B₁₂O₂, B₁₂P₂, and B₁₂As₂ infrared spectra with very well shaped bands could be obtained. The spectrum of B₁₂O₂ with the smallest number of bands was assigned with the aid of a normal coordinate analysis. This gave a good basis for the interpretation of the spectra of normal and ¹⁰B-enriched B₄C and of B₁₂P₂. Both are exhibiting some bands in addition to those expected for the ideal structures, which are explained by the assumption of disordering within the C? B? C resp. P? P groups. At boron carbide this disorder seems to depend on the ratio B:C within its range of homogeneity.     

Thermochemical investigation of Zr doping in LiNi8/12Co2/12Mn2/12O2 based on phase equilibria simulation

The doping behavior of Zr in LiNi_8/12Co_2/12Mn_2/12O₂ (LNCM) is investigated by a simulation of the phase equilibria for the Li-(M^*,Zr)-O system (M^* = Ni, Co, Mn) based on first-principles calculations followed by a thermochemical post-analysis of the resultant phase diagrams. The results indicate that the stable state at the synthetically stoichiometric composition of LNCM with Zr is a mixture of undoped LNCM with a Li₂ZrO₃ secondary phase; doping of Zr in the LNCM crystal is not thermodynamically favored. The energies of various states comprising LNCM supercells with defects, secondary phases, and Zr doping are examined, and the equilibrium doping concentration of Zr is calculated by considering the entire LNCM:Zr crystal as a statistical combination of these states. The doping concentration of Zr in the LNCM crystal is calculated to be very low, which enables balanced control between doping and coating, as recently reported through experimentation. The dopability of Zr is expected to increase with the depletion of O₂ supply during the heating of a system with a precisely controlled Li to M^* ratio, but this behavior is affected by the formation of defects, especially by M^* substitution for Li.     

Hochdrucksynthese von BaSr2P6N12 und BaCa2P6N12 und Strukturvergleich der Reihe BaP2N4, BaCa2P6N12 und BaSr2P6N12

High‐Pressure Synthesis of BaSr₂P₆N₁₂ and BaCa₂P₆N₁₂ and Comparison of the Structures of BaP₂N₄, BaCa₂P₆N₁₂, and BaSr₂P₆N₁₂ The novel nitridophosphates BaCa₂P₆N₁₂ and BaSr₂P₆ N₁₂ were obtained by means of high‐pressure high‐temperature synthesis utilizing the multianvil technique (1200 °C, 5 GPa). The complex anion [PN₂^?] of the title compound is formally isoelectronic with silica. The crystal structure was solved from powder data and refined by the Rietveld method (BaCa₂P₆N₁₂: , Z = 4, a = 9,9578(2) Å; BaSr₂P₆N₁₂: , Z = 4, 10,0705(2) Å). The crystal structures are derived from that of BaP₂N₄ which is isotypic with a high pressure phase of CaB₂O₄ and BaGa₂S₄. For each compound the ³¹P solid state NMR spectrum yielded a single resonance (BaCa₂P₆N₁₂: 7.4 ppm; BaSr₂P₆N₁₂:3.9 ppm).     

[Mo12S12O12(OH)12(H2O)6]: A Cyclic Molecular Cluster Based on the [Mo2S2O2]2+ Building Block

The pH-dependent self-condensation of the [Mo ₂ S ₂ O ₂ ] ²⁺ complex fragment gives the wheellike Mo₁₂ cluster depicted on the right (ball-and-stick model; large balls: S, medium balls: O, small balls: Mo). Applying this synthetic strategy to other starting materials could provide access to other polyoxothiometalates with well-defined cavities.     

The [U2F12]2− Anion of Sr[U2F12]

The D_2h‐symmetric dinuclear complex anion [U₂F₁₂]^2? of pastel green Sr[U₂F₁₂] shows a hitherto unknown structural feature: The coordination polyhedra around the U atoms are edge‐linked monocapped trigonal prisms, the U^V atoms are therefore seven‐coordinated. This leads to a U–U distance of 3.8913(6) Å. A weak U^V–U^V interaction is observed for the dinuclear [U₂F₁₂]^2? complex and described by the antiferromagnetic exchange J_exp of circa ?29.9 cm^?1. The crystalline compound can be easily prepared from SrF₂ and β‐UF₅ in anhydrous hydrogen fluoride (aHF) at room temperature. It was studied by means of single crystal X‐ray diffraction, IR, Raman and UV/VIS spectroscopy, magnetic measurements, and by molecular as well as by solid‐state quantum chemical calculations.     

Synthesis of dialkoxy- and alkoxy-amino-disubstituted derivatives of B12H12 2−

Dichloromethoxymethane reacts with the sodium salt ofcloso-dodecahydrododecaborate Na₂B₁₂H₁₂ to give disubstituted cluster, which readily decomposes when treated with various reagents. This cluster reacts with water, forming the previously described 1,7-B₁₂H₁₀(OH)_{2 2–}reaction with alcohols results in a novel 1,7-dialkoxy derivative, whereas interaction with morpholine in acetone solution affords the novel anion, 1-O-I-Prⁱ-7-O(CH₂CH₂)N-B₁₂H₁₀ ^2–. All of these derivatives were isolated as cesium salts and characterized by one- and two-dimensional NMR techniques.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 421–424, March, 1995.     

Strukturelle Untersuchungen an Cs2[B12H12]

Structural Investigations on Cs₂[B₁₂H₁₂] The crystal structure of Cs₂[B₁₂H₁₂] has been determined from X‐ray single‐crystal data collected at room temperature. Dicesium dodecahydro‐closo‐dodecaborate crystallizes as colourless, face‐rich crystals (cubic, Fm 3; a = 1128.12(7) pm; Z = 4). Its synthesis is based on the reaction of Na[BH₄] with BF₃(O(C₂H₅)₂) via the decomposition of Na[B₃H₈] in boiling diglyme, followed by subsequent separations, precipitations (with aqueous CsOH solution) and recrystallizations. The crystal structure is best described as anti‐CaF₂‐type arrangement with the Cs⁺ cations in all tetrahedral interstices of the cubic closest‐packed host lattice of the icosahedral [B₁₂H₁₂]^2–‐cluster dianions. The intramolecular bond lengths are in the range usually found in closo‐hydroborates: 178 pm for the B–B and 112 pm for the B–H distance. Twelve hydrogen atoms belonging to four [B₁₂H₁₂]^2– icosahedra provide an almost perfect cuboctahedral coordination sphere to the Cs⁺ cations, and their distance of 313 pm (12 ×) attests for the salt‐like character of Cs₂[B₁₂H₁₂] according to {(Cs⁺)₂([B₁₂H₁₂]^2–)}. The ¹¹B{¹H}‐NMR data in aqueous (D₂O) solution are δ = –12,70 ppm (¹J_B–H = 125 Hz), and δ = –15,7 ppm (linewidth: δν_1/2 = 295 Hz) for the solid state ¹¹B‐MAS‐NMR.     

庚烷中C12-EOx-C12•2Br反胶团的形成

在助表面活性剂正己醇存在下, 季铵盐Gemini表面活性剂C12-EOx-C12•2Br(x=1, 2, 3)在正庚烷中形成了反胶团. 以碘光谱法测定了临界反胶团浓度(cmch), 该值小于它们在水中形成正胶团时的临界浓度(cmcaq), 但两者随x的变化规律一致, 均呈单调增长. 反胶团饱和增溶水量随x增加或温度升高而增大.     

Reorientational dynamics of the dodecahydro-closo-dodecaborate anion in Cs2B12H12

Rapid reorientational motions of the B(12)H(12)(2-) icosahedral anion, a key intermediate in borohydride dehydrogenation, are revealed by quasielastic neutron scattering (QENS) measurements of Cs(2)B(12)H(12) between 430 and 530 K. At 430 K, over the range of momentum transfers collected, the elastic incoherent structure factor (EISF) is consistent with a model for reorientational jumps about a single molecular axis. At temperatures of 480 K and higher, however, the EISF suggests the emergence of multiaxis reorientation by dynamically similar, independent jumps about two axes, on average, preserving crystallographic order. Alternatively, if one assumes that the anions are undergoing temperature-dependent rotational trapping, then the EISF is also consistent with a jump model involving a temperature-dependent mobile fraction of anions statistically tumbling between discrete crystallographic sites. Although neutron vibrational spectra demonstrate that the anion torsional modes soften dramatically with increasing temperature, the QENS-derived activation energy of 333 meV for reorientation clearly shows that the anions are not undergoing isotropic rotational diffusion.     

Reaction of closo-dodecaborate anion B12H 12 2− with iminium salts

The reaction of the closo-dodecaborate anion with iminium salts was studied. The iminium salts were either formed in situ or introduced into the reaction in an individual state. Mono-and disubstituted products with an exopolyhedral boron-nitrogen bond were found to form. The structures of compounds 1,7-[NMe₂(CH₂Cl)]₂B₁₂H₁₀ and 1,7-[MeNPh(CH₂Cl)]₂B₁₂H₁₀ were determined using X-ray crystallography.