The niobium and tantalum riddle: gas-phase monocation reactions with pyrene and pyrene-D10

Metal monocation gas-phase reactions with pyrene (Py) have been investigated. Of those cations which bind Py by abstraction of two hydrogen atoms, there are two subgroups of which Nb⁺ and Ta⁺ are the most striking and puzzling representatives. The Ta⁺-like group binds three Py units consecutively, each by expulsion of two hydrogen atoms, whereas the Nb⁺ group binds four Py units; however, in this latter case, the second Py attachment occurs without the expulsion of any hydrogen. When perdeuterated Py-D₁₀ is used, the Ta⁺ group behavior is unaffected, but the Nb⁺ group now exhibits a considerable degree of Py attachment in which no deuterium atoms are lost in the first reaction step. We will attempt to explain this behavior by using the results of reactions of Nb⁺ and Ta⁺ with Py in a Fourier transform mass spectrometer (FTMS).     

Synthesis and crystal structure of pyridine and methanol coordinated α-octabutyloxyphthalocyaninatocobalt (II)

Crystal structure of pyridine and methanol axially coordinated 1,4,8,11,15,18,22,25-octabutyloxyphthalocyaninatocobalt(II)(viz. α-octabutyloxyphthalocyaninatocobalt) [(n-BuO)₈Pc]. Co(Py)(MeOH) (1) was determined by X-ray diffraction methods. Crystal data: monoclinic, space group P2₁/n, Z = 4, a = 1.06482(4), b = 3.5487(2), c = 1.79428(9) nm, β=103.246(2)°, V = 6.5792(5) nm³, μ = 0.325 mm^-1. The result shows that the ring skeleton of 1 maintains planar conformation, which is similar to that of unsubstituted phthalocyanine but is remarkably different from the saddle shape conformation of 1,4,8,11,15,18,22,25-octabutyloxyphthalocyaninatocopper (II) [(n-BuO)₈Pc]Cu(2), which has no axial coordination. In the structure of 1, the substituents butyloxy groups of 1 somewhat deviate from the ring plane, while pyridine and methanol are coordinated to the center atom Co from opposite sides of the ring plane. In addition, all molecules are stacked along axis a to form one-dimensional molecule chain, the neighboring molecules in the chain overlap to some extent with a benzene ring and a distance of 0.3565 nm.     

SYNTHESIS AND CHARACTERIZATION OF PALLADIUM COORDINATING IMINE SIDE CHAIN LIQUID CRYSTALLINE POLYSILOXANES

New thermotropic chloro-bridged dinuclear palladium coordinating imine side chain liquid crystalline polysiloxanes have been synthesized. Their mesomorphic properties have been investigated by DSC, X-ray diffraction and polarizing microscopy. The polymeric complexes show nematicdiscotic (Nd) mesophase. It is found that the temperature range of liquid crystalline state of chloro- bridged polymeric complexes is much wider than that of acetato- bridged ones and imine side chain polysiloxane. This indicates that the disc-like chloro-bridged palladium complexing units play a role as mesogen in mesophase.     

Magnetic properties of group VIB hexacarbonyls. Suggestion of a new diamagnetic susceptibility standard

Summary Careful measurements of the magnetic susceptibilities of group VI B metal hexacarbonyls show an ideal diamagnetic behaviour. The properties of W(CO)₆, together with the relatively low price, lead to the suggestion of W(CO)₆ as a new calibration standard for the diamagnetic region.

---

Magnetische Eigenschaften von Hexacarbonylen der Gruppe VI B. Vorschlag zu einem neuen diamagnetischen Suszeptibilitätsstandard

Zusammenfassung Sorgfältige Messungen der magnetischen Suszeptibilität der Metallhexacarbonyle der Gruppe VI B zeigen deren ideal diamagnetisches Verhalten. Die physikalischen Eigenschaften des W(CO)₆, zusammen mit dem relativ niedrigen Preis, prädestinieren es als diamagnetischen Eichstandard.

     

The synthesis and properties of adducts between poly(4-vinyl pyridine) and metal alkyls

Poly(4-vinyl pyridine) is used as a polymeric ligand to react with metal alkyls, Me_nM (n = 3, M = Al, Ga or In; n = 2, M = Cd or Zn) to form adducts. The adducts are characterized by solid state ¹³C NMR, infrared spectroscopy, microanalyses and differential scanning calorimetry (DSC). All the adducts are nonpyrophoric and thermally dissociable, so they may have potential both for use in adduct purification processes or for use as safer metal alkyl sources for Metal–Organic Chemical Vapor Deposition.     

Peculiarities in the Raman spectra of ZrB12 and LuB12 single crystals

We have measured Raman spectra of high-quality Zr^natB₁₂, Lu^natB₁₂ and Lu¹¹B₁₂ single crystals with high resolution, and the observed strong peaks are attributed to specific vibration modes. Besides, there are a number of additional Raman peaks in spectral ranges, where only Raman-inactive vibrations of the atomic arrangement are expected. Accordingly, it is assumed, that the investigated crystals contain intrinsic structural imperfections or distortions in sufficient concentration and efficiency to initiate the observed breaking of phonon selection rules. We suppose boron vacancies, boron isotope effects and displacements of the metal atoms to be reasons for such imperfections.     

A concise enantioselective synthesis of the fungal metabolite (+)-decarestrictine L

A stereoselective 10-step synthesis of the fungal metabolite (+)-decarestrictine L from commercially available ethyl (R)-3-hydroxybutyrate is described in which tandem oxonium ylide formation and rearrangement is used to construct the tetrahydropyranyl core of the natural product.     

金属酞菁配合物的从头计算研究

利用从头计算方法研究了6种金属酞菁MPc(M=Zn2+、Cu2 +、Ni2+、Co2+、Fe2+、Mn2+)。得到了它们的基态能量,基态自旋多重度,分子轨道组成与能级,电荷分布与键序。其中,自旋多重度的计算结果与实验相符。中心离子d轨道参与HOMO、LUMO构成的程度可以解释各MPc光敏活性不同的实验现象。     

Pd/Al2O3催化剂的高温热烧结研究

以汽车尾气净化催化剂为背景，用溶胶－凝胶法和浸渍法制备了低负载量贵金属单钯燃烧催化剂。通过ＸＲＤ宽化法检测了在１２７３Ｋ的模拟反应气流中烧结２４ｈ后催化剂上Ｐｄ晶粒大小的变化。     

酞菁铑的合成及其性质研究

本文合成了铑(Ⅲ)酞菁配合物,用循环伏安法研究了该配合物在二甲基甲酰胺、吡啶和二甲亚砜等有机溶剂中的电化学,并利用薄层透光电极电解;获得了该配合物四种不同氧化态时的电子光谱,并对电极反应机理及其产物进行了讨论.