Zur Bildung und Struktur der Phosphinophosphiniden-phosphorane tBu2P?PP(Me)tBu2 1, tBu(Me3Si)P?PP(Me)tBu2 2 und tBu2P?PP(Br)tBu2 3

Synthesis and Structure of Phosphinophosphinidene-phosphoranes tBu₂P? P?P(Me)tBu₂ 1, tBu(Me₃Si)P? P?P(Me)tBu₂ 2, and tBu₂P? P?P(Br)tBu₂ 3 A new method for the synthesis of 1 and 2 (Formulae see ?Inhaltsübersicht”?) is reported based on the reaction of 5 with substitution reagents (Me₂SO₄ or CH₃Cl). The results of the X-ray structure determination of 1 and 2 are given and compared with those of 3 . While in 3 one P? P distance corresponds to a double bond and the other P? P distance to a single bond (difference 12.5 pm) the differences of the P? P distances in 1 and 2 are much smaller: 5.28 pm in 1 , 4.68 pm in 2 . Both 1 and 2 crystallize monoclinic in the space group P2₁/n (Z = 4). 2 additionally contains two disordered molecules of the solvent pentane in the unit cell. Parameters of 1 : a = 884.32(8) pm, b = 1 924.67(25) pm, c = 1 277.07(13) pm, β = 100.816(8)°, and of 2 : a = 1 101.93(12) pm, b = 1 712.46(18) pm, c = 1 395.81(12) pm, β = 111.159(7)°, all data collected at 143 K. The skeleton of the three P atoms is bent (PPP angle 100.95° for 1 , 100.29° for 2 and 105.77° for 3 ). Ab initio SCF calculations are used to discuss the bonding situation in the molecular skeleton of the three P atoms of 1 and 3 . The results show a significant contribution of the ionic structure R₂P? P(^?)? P(⁺)(X)R₂. The structure with (partially) charged P atoms is stabilized by bulky polarizable groups R (as tBu) as compared to the fully covalent structure R₂P? P(X)? PR₂.     

Optoacoustic Laser Stark spectroscopy and FIR laser action on CH3Br using a waveguide CO2 laser

The optoacoustic spectrum of CH₃Br around 10 m band lines of a tunable cw waveguide CO₂ laser is investigated. Several new infrared absorptions are observed and most of the correspond ing molecular transitions are assigned. Far infra red laser action is reported by pumping with the same CO₂ laser: pump offsets are given using the Transferred Lambs dip (TLD) technique. A new FIR laser emission is obtained and assigned. An optoacoustic Laser Stark spectroscopy technique is used to investigate off resonance infrared tran sitions.     

掺溴聚-4-甲基-1-戊烯的合成研究

 液溴与聚-4-甲基-1-戊烯（PMP）的四氯化碳溶液反应，在光照条件下得到溴代PMP，通过红外与元素分析确证了其结构。并通过热重分析对其性能进行了初步的研究。研究发现，在光照条件下溴原子很容易与PMP中叔丁基上的氢原子发生取代反应，得到化学掺杂溴原子的聚合物。该聚合物在150℃以下比较稳定，在150℃以上就会失去HBr。采用此种方法，可得到掺杂均匀的低密度材料。     

A Pd4Br4 macrocycle trapped by cocrystallization from a highly dynamic equilibrium of η3‐cycloheptatrienide complexes

In the coordination chemistry of palladium, dimers bridged via halides are a common motif. Higher oligomers, however, are still rare. We report the structure of an alternating eight‐membered [Pd₄Br₄]⁴⁻ ring framed by cycloheptatrienide ligands, which was obtained by cocrystallization of dimers and tetramers of the complex salt bromido{η³‐[3‐(2,6‐diisopropylphenyl)imidazolium‐1‐yl]cycloheptatrienido}palladium(II) tetrafluoroborate, namely bis[di‐μ‐bromido‐bis({η³‐[3‐(2,6‐diisopropylphenyl)imidazolium‐1‐yl]cycloheptatrienido}palladium(II))] cyclo‐tetra‐μ‐bromido‐tetrakis({η³‐[3‐(2,6‐diisopropylphenyl)imidazolium‐1‐yl]cycloheptatrienido}palladium(II)) octakis(tetrafluoroborate) dichloromethane octasolvate, [Pd₄Br₄(C₂₂H₂₆N₂)₄][Pd₂Br₂(C₂₂H₂₆N₂)₂]₂(BF₄)₈·8CH₂Cl₂. These dimers and tetramers form a highly dynamic equilibrium in solution which was studied by low‐temperature NMR spectroscopy. In the light of the presented results, tetrameric Pd^II species can be assumed to co‐exist as a second species in many cases where by current knowledge only a dimeric compound would be expected.     

Rate constants of the reactions of O(3P) atoms with Br2 and NO2 over the temperature range 220-950 K

The kinetics of the reactions of Br₂ and NO₂ with ground state oxygen atoms have been studied over a wide temperature range, T = 220-950 K, using a low-pressure flow tube reactor coupled with a quadrupole mass spectrometer: O + NO₂ → NO + O₂ (1) and O + Br₂ → Br + BrO (2). The rate constant of reaction (1) was determined under pseudo–first-order conditions, either monitoring the kinetics of O-atom or NO₂ consumption in excess of NO₂ or of the oxygen atoms, respectively: k₁ = (6.1 ± 0.4) × 10⁻¹² exp((155 ± 18)/T) cm³ molecule⁻¹ s⁻¹ (where the uncertainties represent precision at the 2σ level, the estimated total uncertainty on k₁ being 15% at all temperatures). The temperature dependence of k₁, found to be in excellent agreement with multiple previous low-temperature data, was extended to 950 K. The rate constant of reaction (2) determined under pseudo–first-order conditions, monitoring the kinetics of Br₂ consumption in excess of O-atoms, showed upward curvature at low and high temperatures of the study and was fitted with the following three-parameter expression: k₂ = 9.85 × 10⁻¹⁶ T^1.41 exp(543/T) cm³ molecule⁻¹ s⁻¹ at T = (220-950) K, which is recommended from the present study with an independent of temperature conservative uncertainty of 15% on k₂.     

Br-掺杂Bi2WO6的水热法合成及其可见光催化性能

以Bi（NO₃）₃·5H₂O和Na₂WO₄·2H₂O为主要原料,采用水热法合成了纯相Bi₂WO₆,并对其进行非金属离子Br^-掺杂改性。采用XRD、SEM、TEM、XPS、Raman、PL和DRS研究了Br^-掺杂对Bi₂WO₆的物相结构、形貌和可见光催化性能的影响。结果表明,Br^-掺杂可有效提高Bi₂WO₆的可见光催化性能,当掺杂量（物质的量百分数）为8%时,溴掺杂Bi₂WO₆的光催化性能最好,可见光照射40 min后,可降解96.73%的罗丹明-B,与未掺杂Bi₂WO₆相比,其降解率提高了36.32%。     

Three-Component,One-Pot Synthesis of Benzo[b][1,4]oxazines in Ionic Liquid 1-Butyl-3-methylimidazolium Bromide

Benzo[b][1,4]oxazines have been synthesized in good to excellent yields in the presence of the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]Br under relatively mild conditions without any added catalyst, The method offers the advantages of good yields and short reaction times, and the ionic liquid can be easily separated from the product and reused.     

Efficient Microscale Preparation of Isotopically Enriched 1‐[79Br]Bromo‐2‐Fluoroethylene, [79Br]BrHC˭CHF

Abstract

An efficient preparation of 1‐[⁷⁹Br]bromo‐2‐fluoroethylene, [⁷⁹Br]BrHC?CHF, was carried out by a three‐step procedure: (a) natural 1‐bromo‐2‐fluoroethylene, BrHC?CHF, was iodinated to 1‐fluoro‐2‐iodoethylene, FHC?CHI; (b) 1‐fluoro‐2‐iodoethylene was ⁷⁹Br₂‐brominated to 1,2‐di[⁷⁹Br]bromo‐1‐fluoro‐2‐iodoethane, [⁷⁹Br]BrFCHCH[⁷⁹Br]BrI; and (c) 1,2‐di[⁷⁹Br]bromo‐1‐fluoro‐2‐iodoethane was dehalogenated to 1‐[⁷⁹Br]bromo‐2‐fluoroethylene, [⁷⁹Br]BrHC?CHF. The yield of isolated product, on a 2‐mmol scale, was 62% with respect to ⁷⁹Br₂.     

HZSM-5分子筛中邻近酸中心上的协同催化作用

总结了HZSM-5分子筛中邻近的酸中心协同催化作用的研究进展, 包括布朗斯特酸(B酸)和路易斯酸 (L酸)的协同催化、 B酸和B酸的协同催化作用. 综述了通过多种表征手段下协同催化作用机理的研究进展, 以及实验与理论计算相结合并相互验证的研究结果, 对邻近酸中心协同作用下反应分子的共同吸附、 活化与转化路径的特点进行了分析与总结, 提出了对邻近酸中心协同催化作用进行深入研究的关键科学问题和可能的解决方案.     

FER分子筛中铝原子的受限落位

分子筛是一类具有规则孔道或笼状结构的多孔材料,因其独特的结构和可调的酸性而广泛用于石油化工、精细化学品合成、现代煤化工等诸多行业.2006年Iglesia等在具有8元环孔道结构/侧口袋的FER和MOR分子筛上实现了无卤素添加、无贵金属存在条件下,由二甲醚羰基化合成乙酸甲酯的反应.乙酸甲酯通过进一步加氢可实现煤基乙醇的绿色生产.MOR分子筛通常具有较高的催化活性,但失活迅速;FER分子筛表现出良好的催化稳定性,但活性较低.如何在保证FER分子筛稳定性的前提下,进一步提升其羰基化活性是目前研究的热点.前期理论和实验研究发现,二甲醚羰基化反应活性与分子筛8元环孔道中的Br?nsted酸位密度存在正相关.因此,通过优化合成条件,选择性调控铝原子分布在"ferrierite"笼中,可以提高FER分子筛的羰基化反应活性.尽管研究者已在调节FER分子筛铝分布方面进行了大量研究,但对于不同T位上Al原子的精准识别以及对应Br?nsted酸位的可接触性还缺少系统和深入的认识.本文选取了几种代表性模板剂,分别在碱性和含氟体系下制备了系列FER分子筛样品,利用Rietveld精修和模拟退火算法,在原子水平揭示了模板剂种类以及合成介质变化对Al原子在不同T位分布的影响,并结合二甲醚羰基化反应进行了结构和性能的关联.首先选取不同尺寸大小的环状胺(环己胺、哌啶、吡啶、吡咯烷)和链状胺(乙二胺)合成了具有相似形貌、孔结构、酸密度的系列FER分子筛样品.以CHA-Na-FER为例,PXRD精修结果显示,Na+(平衡35％的骨架负电荷)分布在10元环孔道中与O1形成氢键,质子化的环己胺分布在"ferrierite"笼中,并且环己胺上的N与O3形成氢键.这说明与O1相连的T3位以及与O3相连的T1位都有可能是Al富集的位置.为了进一步验证该结论,本文还精修了吸附探针分子吡啶的样品CHA-Na-FER-Py-60h.原粉以及吸附吡啶样品的精修结果表明,T1位和T3位是样品中铝富集的位置.随后,运用相同方法研究了Py-Na-FER,PI-Na-FER,En-Na-FER和Pyrr-HF-FER样品中的Al落位,发现T1/T3位均是样品中Al富集的位置.此外,理论计算结果表明T1/T3位上Al原子的取代能较低,说明Al优先取代T1/T3位上的Si,这与精修结果相一致.前期理论模拟结果表明,FER分子筛中T2-O5和T4-O7位点的CO插入反应能垒较低,是二甲醚羰基化反应的活性位.本文吡啶吸附实验、热重分析以及PXRD精修结果表明,FER分子筛中大部分Al富集在T1/T3位,与T2/T4位相关的Br?nsted酸约占18％～30％.最后,对各样品进行了二甲醚羰基化反应评价,结果显示PI-Na-FER,Py-Na-FER,En-Na-FER和CHA-Na-FER催化剂的乙酸甲酯生成速率相近,约为0.10 mol/(mol H+?h).Pyrr-HF-FER催化剂的乙酸甲酯生成速率最高,可达到0.16 mol/(mol H+?h),这可能是由于Pyrr-HF-FER催化剂具有更多T2/T4位相关的Br?nsted酸.虽然Pyrr-HF-FER催化剂的乙酸甲酯生成速率较其他四个催化剂有一定提升,但其仍远低于MOR分子筛上乙酸甲酯生成速率(0.40 mol/(mol H+·h)).综上,有机模板剂的选择与合成介质的改变对FER分子筛中Al分布的调控作用是有限的,即Al原子总是优先分布于T1/T3位.而与T1和T3位相关的Br?nsted酸位不是二甲醚羰基化反应的活性位点.因此与MOR相比,FER分子筛在二甲醚羰基化反应中表现出较低的催化活性.