Prepared Low Stress Cubic Boron Nitride Film by Physical Vapor Deposition

We present low stress cubic boron nitride (cBN) films with a transition layer deposited on the metal alloy substrates by tuned substrate radio-frequency magnetron sputtering. The films were characterized by Fourier transform infrared spectroscopy and transmission electron microscopy (TEM). The IR peak position of cubic boron nitride at 1006.3 cm⁻¹, which is close to the stressless state, indicates that the film has very low internal stress. The TEM image shows that pure CBN phase exists on the surface of the film. Several phases of boron nitride were found at the medium implantation dose. It is believed that the transition from the low ordered phases to cBN phase occurred during implantation.     

Boron implantation in Si: Channeling effects studied by SIMS and simulation

The axial channeling behaviour of boron implants in <100>, <110> and <111> silicon wafers is investigated by SIMS. Large differences of channeling characteristics such as channeled projected range (the projected range of channeled ions or channeling peak) and the fraction of channeled to implanted ions are observed among the three major crystal orientations. Within the critical angle, the channeling behaviour is very sensitive to the incidence beam angle with respect to crystal orientations. SIMS measurements are performed at different positions along several critical directions over a whole wafer. Well channeled profiles with an incidence beam angle to crystal orientations of 0 ° are obtained for each ion implantation energy and orientation. The results are used to test various models of ion implantation by simulation. A 3-parameter model for electronic stopping power of boron in silicon was proposed.     

Alternativ-Liganden. XXII. Rhodium(I)-Komplexe mit Donor/Akzeptor-Liganden des Typs Me2PCH2CH2SiXnMe3−(X = F,Cl, OMe)

Alternative Ligands. XXII. Rhodium(I) complexes with Donor/Acceptor Ligands of the Typs Me₂PCH₂CH₂SiX_nMe_3?n(X = F, Cl, OMe) Donor/acceptor ligand of the type Me₂PCH₂SiX_nMe_3?n react with [Rh(CO)₂Cl]₂ ( 1 ) to give the mononuclear complexes RhCl(CO)(PMe₂CH₂CH₂SiX_nMe_3?n)₂ ( 2-6 , Table 1) with planar geometry of the donor atoms, one exception being Me₂PCH₂CH₂CH₂SiCl₃, yielding the crystalline Rh^III-complex RhCl₂(CO)(PMe₂CH₂CH₂SiCl₂)(PMe₂CH₂CH₂SiCl₃) ( 7 ) by oxidative addition of one of the SiCl bonds to the Rh¹ precursor. Structures with Rh → Si interaction between the basic central atoms and the acceptor group SiX_nMe_3?n could be detected in the isolated products neither spectroscopically nor by X-ray diffraction of the two representatives RhCl(CO)(PMe₂CH₂CH₂SiF₃)₂ ( 2 ) and RhCl(CO)[PMe₂CH₂CH₂siF₃]₂ ( 2 ) and RhCl(CO) [PMe₂CH₂CH₂Si(OMe₃]₂ ( 6 ). The presence of such acid/base adducts in the reaction mixture is indicated for the more acidic acceptor groups SiX_nMe_3?n byv_co values near 1990cm^?1, (see Table 3). The complex RhCl(CO)PMe₃)(PMe₂CH₂CH₂SiF₃ ( 8 ) is obtained by the reaction of RhCl(CO)(PMe₃)₂ ( 9 ) with Me₂PCH₂SiF₃ and has been identified spectroscopically in a mixture with 2 and 9 .     

Rhodium (II) compounds with functionalized metalated phosphines as bridging ligands

The reaction of Rh₂(O₂CCH₃)₄ · 2CH₃OH with the phosphine P(4-BrC₆H₄)₂(C₆H₅), 2, results in the formation of the monometalated compound Rh₂(O₂CCH₃)₃[PC] · 2CH₃CO₂H (PC representing a metalated P(4-BrC₆H₄)₂(C₆H₅)). The reaction involves selective metalation of the phosphine at one Br-substituted ring (12:1 isomer ratio). The reaction of Rh₂(O₂CCH₃)₃[(4-BrC₆H₃)P(4-BrC₆H₄)(C₆H₅)] · 2CH₃CO₂H, 4, with one additional mol of triphenylphosphine yields a mixture of two main stereoisomers Rh₂(O₂CCH₃)₂[(4-BrC₆H₃)P(4-BrC₆H₄)(C₆H₅)] [(C₆H₄)P(C₆H₅)₂] · 2CH₃CO₂H, 5a and 5b, that were isolated as pure compounds. These two compounds were resolved in the corresponding M and P enantiomers as trifluoroacetate derivatives that show good enantioselectivities in catalytic transformation of α-diazocarbonyl compounds.     

Thermoregulated Liquid/Liquid Biphasic Catalysis and Its Application

A brief overview of our recent research results of thermoregulated liquid/liquid biphasic catalysis is presented. Emphasis is given to the general principles of thermoregulated phase-transfer catalysis (TRPTC) and thermoregulated phase-separable catalysis (TPSC). In addition, the applications of TRPTC and TPSC in biphasic catalysis are also discussed. The introduction of TRPTC to biphasic system is free from the shortcomings of classical aqueous/organic two-phase catalysis, in which the application scope is restrained by the water solubility of the substrate. Meanwhile, TPSC provides a very simple and reliable way to deal with the separation of catalyst in homogeneous catalysis. The common advantages of TRPTC and TPSC are characterized by homogeneous catalysis coupled with convenient biphasic separation.     

Coordination solids via assembly of adaptable components: systematic structural variation in alkaline earth organosulfonate networks

A family of alkaline earth organosulfonate coordination solids is reported. In contrast to more typical crystal engineering approaches, these solids are sustained by the assembly of building blocks that are coordinatively adaptable rather than rigid in their bonding preferences. The ligand, 4,5-dihydroxybenzene-1,3-disulfonate, L, progressively evolves from a 0D, 1D, 2D, to a 3D microporous network with the Group II cations Mg(2+), Ca(2+), Sr(2+), and Ba(2+), (compounds 1-4), respectively. This trend in dimensionality can be explained by considering factors such as hard-soft acid-base principles and cation radii, a rationalization which follows salient crystal engineering principles. The selective gas sorption properties of the microporous 3D network [Ba(L)(H(2)O)].H(2)O, 4, with different gaseous guests are also presented.     

Properties and Characterization of Modified HZSM—5 Zeolites

Physicochemical and catalytic properties of phosphorus and boron modified HZSM-5 zeolites treated with 100% steam at 673K were investigated.The acidity and distribution of acidic sites were studied by infrared spectroscopy using pyridine as probe molecule and temperature programmed desortion (TPD) of ammonia.The structure of the samples was characterized by XRD,and the textural properties of the catalysts were determined by nitrogen isothermal adsorption-desorption measurements and scanning electron microscopy(SEM).The XRD results show that the modified samples have no novel crystalline phase,indicating a high dispersion of phosphorus and boron species.After treatment,the microporous volume and surface area of the samples markedly decrease,implying the bolockage of the channel.The nitrogen adsorption-desorption measurements suggest that the isothermal type of all samples is a combination of isothermal type Ⅰ and Ⅳ，and all hysteresis loops resemble the H4-type in the IUPAC classification.The total acidity of the modified samples,determined by pyrldine adsorption IR and TPD of ammonia,decreases in contrast to that of the parent HZSM-5.The conversion of n-heptane over P and B steammodified HZSM-5 is higher than that of P and B-modified HZSM-5 zeolites but lower than that of the parent HZSM-5.     

New developments in the Pd-catalysed cyclisation-coupling reaction of alkene-containing carbonucleophiles with organic halides (and triflates). The first examples of asymmetric catalysis.

The results of our preliminary investigations directed toward asymmetric catalysis of the cyclocarbopalladation of alkenes bearing a proximate nucleophile with organic halides (or triflates) are disclosed. A series of bidentate phosphine ligands were evaluated in intramolecular versions of this reaction using (E)-2-[7-(2-bromophenyl)-hept-4-enyl]-malonic acid dimethyl ester (1) and (Z)-2-[7-(2-trifluoromethanesulfonyloxy-phenyl)-hept-4-enyl]-malonic acid dimethyl ester (9) as model substrates. The highest enantioselective induction was obtained with aryl triflate 9 which produced the corresponding cyclopentylindane as a single diastereomer in 54% chemical yield and 43% ee by using PdCl₂[S-(−)-TolBINAP] as chiral catalyst and K₂CO₃ as base.     

Bi- and trinuclear oxalamidinate complexes of palladium as catalysts in the copper-free Sonogashira reaction and in the Negishi reaction

The binuclear complex [(acac)Pd(oxam)Pd(acac)] 1 (oxam: tetraphenyl oxalic amidinate) has been prepared from H₂oxam and Pd(acac)₂ in excellent yield. The complex was characterized by elemental analyses, mass spectroscopy, ¹H NMR, ¹³C NMR spectroscopy and in the solid state by X-ray single crystal diffraction analyses. 1 consists of a bimetallic centrosymmetric unit in which the planar oxam ligand acts in a bis-chelating fashion. Each palladium center is in a planar environment.The complex 1 acts as highly selective pre-catalyst in the copper-free Sonogashira reaction between 4-bromoacetophenone and phenylacetylene. Its long-time catalytic activity is higher than that of the related binuclear complex 2 (oxam: tetra-p-tolyl oxalic amidinate) or that of the trinuclear compound [(acac)Pd(oxam)Zn(oxam)Pd(acac)] (3), the solid-state structure of which was also determined by an X-ray structural analysis of single crystals. In addition, 2 is an active and extremely selective pre-catalyst for the Negishi reaction between 3,5,6,8-tetrabromophenanthroline and R-CC-ZnCl (R: Ph, (ⁱprop)₃Si) to form tetra-alkyne-substituted derivatives.     

Ni-B和Ni-Ce-B超细非晶态合金的退火晶化及其催化性能

 采用XAFS,XRD和DTA方法研究了Ni－B和Ni－Ce－B超细非晶态合金在退火过程中的结构变化及其结构与催化性能的关系．活性结果表明,在退火温度为623K时,Ni－B和Ni－Ce－B样品的苯加氢催化反应转化率最高,分别为63％和81％,0．3％Ce的掺入提高了Ni－Ce－B的催化活性．DTA结果表明,Ni－B超细非晶态合金在598和653K有两个晶化峰,而Ni－Ce－B样品有548,603,696和801K四个晶化峰．XAFS和XRD结果进一步说明,在573K退火时,Ni－B样品晶化生成晶态Ni3B和纳米晶Ni,此时Ni－Ce－B仅有少量晶态Ni3B生成．在673K退火时,Ni－B样品中的Ni3B开始分解生成晶态Ni,同时纳米晶Ni聚集并形成大颗粒晶态Ni,而Ni－Ce－B样品晶化生成晶态Ni3B和纳米晶Ni．在773K和更高的温度退火处理后,Ni－B样品中Ni的局域环境结构与金属Ni箔基本一致,但Ni－Ce－B样品晶化生成的Ni晶格有较大畸变,同时Ni3B并未分解．说明0．3％的Ce对提高Ni－Ce－B样品的稳定性有显著作用．本文首次报道了Ni－B和Ni－Ce－B超细非晶态合金中苯加氢催化活性中心为纳米晶Ni和类似于金属Ni的Ni－B非晶态合金．