过渡金属钌、铑配合物在室温离子液体中催化硅氢加成反应的研究

研究了在室温离子液体以及室温离子液体/有机溶剂复合介质体系中, Rh(PPh₃)₃Cl, Ru(PPh₃)₃Cl₂等催化烯烃与三乙氧基硅烷的硅氢加成反应. 实验结果表明, 在乙二醇二甲醚/离子液体1-丁基-3-甲基咪唑六氟磷酸盐(BMImBF₆) (V/V＝1/4)介质中, 于90 ℃下, 己烯与三乙氧基硅烷反应的转化率为100%, β加成物的选择性可达89.0%. 而用Rh(PPh₃)₃Cl作为反应的催化剂, 在纯离子液体BMImPF₆中, 就可以高效催化烯烃与三乙氧基氢硅烷的加成反应. 过渡金属Rh(PPh₃)₃Cl, Ru(PPh₃)₃Cl₂催化剂/离子液体BMImPF₆催化体系, 不仅解决了产物与催化剂分离困难这一难题, 同时, 离子液体BMImPF₆的存在提高了过渡金属Rh(PPh₃)₃Cl, Ru(PPh₃)₃Cl₂催化硅氢加成反应的活性, 特别是β加成物的选择性. 反应结束后, 催化剂/离子液体与产物易于分离, 并且可以重复使用.     

稀土金属配合物催化的甲胺基硼烷脱氢聚合反应

报道了稀土金属配合物催化的胺基硼烷脱氢聚合反应.双茂稀土烷基配合物[(C₅Me₄R)₂LnR’,R=Me,H;Ln=Sc,Y;R’=CH₂Si Me₃,CH(SiMe₃)₂]可以有效地实现甲基胺基硼烷(Me NH₂·BH₃,MAB)脱氢反应,生成相应的硼氮聚合物[(Me NH-BH₂)_n,PMAB].研究表明随着稀土金属离子半径的增大或者茂基配体空间位阻的减小,聚合活性会随之降低.在机理研究中,通过催化剂与底物的化学计量反应,成功分离得到一例具有β-B-agostic结构的钪胺基硼烷配合物;同时通过控制实验证实了活性的钪氢中间体可能为催化活性物种.     

钯配合物对结核杆菌RecA intein蛋白质剪接的抑制作用

研究了5种钯配合物Pd(bipy)Cl₂, Pd(phen)Cl₂, [Pd(dien)Cl]Cl, trans-Pd(NH₃)₂Cl₂和cis-Pd(NH₃)₂Cl₂对结核杆菌RecA intein蛋白质剪接的抑制作用. 结果表明, trans-Pd(NH₃)₂Cl₂的抑制活性最好, IC₅₀=3.3×10^-5 mol/L. 钯配合物通过与intein的第一个氨基酸(半胱氨酸)配位, 从而抑制蛋白质的剪接活性. 荧光猝灭的动力学数据表明, 配体的大小会明显影响钯配合物与intein的相互作用, 配体越大, 作用越慢.     

硼-10富集硼烷Lewis碱加合物的合成

天然硼中主要含有两种稳定同位素,即硼-10和硼-11,丰度分别为19.78%和80.22%.其中,富集的硼-10同位素在核工业以及放射治疗癌症等方面有重要应用.因此,硼-10富集含硼化合物的合成具有重要的研究意义.硼烷类化合物是合成这类化合物的主要起始原料,但是目前合成硼-10富集硼烷化合物的方法还比较少.以商业可得的硼-10富集硼酸为起始原料,首先采用改进的文献方法合成了硼-10富集的Na¹⁰BH₄,Na¹⁰BH₄与碘单质反应生成乙硼烷(¹⁰B₂H₆)然后,乙硼烷与各种Lewis碱进行配位,得到了一系列硼-10富集的硼烷Lewis碱加合物,包括四氢呋喃硼烷(THF·¹⁰BH₃)、二甲基硫醚硼烷(DMS·¹⁰BH₃)、N,N-二甲基苯胺硼烷(DMA·¹⁰BH₃)、氨硼烷(NH₃·     

水合铵硼氧酸盐及其饱和溶液的FTIR和Raman光谱研究

研究了NH₄B₅O₈·4H₂O和(NH₄)₂B₈O₁₃·6H₂O及其饱和溶液于20℃的FTIR和Raman光谱,对振动频率进行了归属.根据振动光谱特征,预测(NH₄)₂B₈O₁₃·6H₂O中所含基本结构单元为[B₇O ₁₁(OH)·B(OH)₃]^2-.首次将Raman光谱中516cm^-1处的强散射峰归属为这一多聚硼氧配阴离子的对称脉冲振动峰,并对以上2种铵硼氧酸盐饱和溶液中硼氧配阴离子的存在形式{B(OH)₃,[B₃O₃(OH)₄]^-和[B₅O₆(OH)₄]^-}和相互作用机理进行了探讨.     

有机胺盐/硼烷体系与炔烃的硼氢化加成反应机理研究

炔烃的立体选择性硼氢化加成反应是有机合成中重要的反应之一.在硅烷的存在下,有机胺盐酸盐/硼烷体系可与炔烃在温和的反应条件下发生计量的加成反应.该反应不仅可高立体选择性地得到Z-式构型的1,2-硼氢化胺盐加成产物,而且反应产率高,产物易于分离提纯.对有机胺盐酸盐/硼烷体系与炔烃的加成反应机理进行的研究表明,胺盐与B（C₆F₅）₃及硅烷反应所生成的硼氢化胺盐"[R₂NH₂]⁺[H-B（C₆F₅）₃]^-",虽然被认为是受限路易斯酸碱对化学的活性中间体,但其本身并不能直接还原炔烃;炔烃必须首先被催化量的路易斯酸B（C₆F₅）₃活化后才可与[H-B（C₆F₅）₃]-加成.同时,胺盐氯阴离子Cl-与路易斯酸B（C₆F₅）₃之间的弱的相互作用直接决定着产物的立体选择性,[H-B（C₆F₅）₃]^-以反式加成的方式进攻活化后的炔烃最终得到Z-式构型的硼氢化加成产物.     

顺-[Pt(NH3)2Cl2]与核苷的作用

用分光光度法研究了37℃、pH=5.5、0.1M NaClO₄介质中cis[Pt(NH₃)₂Cl₂]和DNA组成物--鸟嘌呤核苷、腺嘌呤核苷、胞嘧啶核苷及胸腺嘧啶核苷的作用。发现顺-[Pt^Ⅱ(NH₃)₂]与前三种核苷能生成组成为1:1、1:2二种络合物,与胸腺嘧啶核苷不作用。所测得一级和二级表观生成常数,以及作用初速分别有如下大小次序:Guo>Ado>Cyt》Thy;Guo>Ado>Cyt》Thy.在所得结果基础上讨论了顺-[Pt(NH₃)₂Cl₂]和癌细胞中DNA作用的可能方式。     

氨硼烷催化水解制氢

氢气作为全球公认的清洁能源载体,备受关注。寻找安全高效的储氢材料以转型到氢能社会是当前氢能应用面临最大的挑战之一。氨硼烷(NH₃BH₃,AB)具有非常高的储氢质量分数(19.6 wt%)和体积储氢密度(0.145 kgH₂/L),因其在储氢和放氢性能方面的显著优势,被认为是一种颇具应用潜力的化学储氢材料。氨硼烷能够通过热解、醇解和水解放出氢气。其中,氨硼烷水解制氢可以通过催化剂进行可控放氢,且具有反应条件温和、不产生CO(易使催化剂中毒)等优点,被认为是一种安全高效和实用性强的制氢技术。本文简要介绍了氨硼烷的性质和合成,阐述了氨硼烷水解制氢的机理,综述了近年来氨硼烷水解制氢催化剂的研究进展,分析了碱对氨硼烷水解制氢的促进作用,并讨论了水解产物回收利用问题。     

钨的原子簇化合物研究(Ⅰ)——九氯二钨酸盐的EXAFS和单晶结构分析

在实验室转靶EXAFS装置上测定了钨原子簇化合物K₃W₂Cl₉,(NHD₄)₃W₂Cl₉,(Bu₄N)₃W₂Cl₉的阴离子结构.在ENRAF-NONIUSCAD-4四圆单晶衍射仪上测定了(NH₄)₃W₂Cl₉的晶体结构。在实验误差范围内,W₂Cl₉^3-结构的EXAFS结果与单晶结果符合较好。实验结果表明,在与不同的一价阳离子结合时,阴离子W₂Cl₉^3-仍保持双共面八面体的结构。由于其中强烈的W-W金属多重键结合,使得整个阴离子的骨架和键长都没有显著变化。     

双二苯基-1-甲基咪唑膦氯化镍的制备及其电催化还原CO2的研究

以二苯基-1-甲基咪唑膦（dpim）为配体制备了一种新型的配合物催化剂Ni(dpim)₂Cl₂. 循环伏安研究表明,Ni(dpim)₂Cl₂配合物在氮气气氛下表现出两步还原的电化学行为,在-0.7 V下为两电子的不可逆还原,在-1.3 V下为单电子准可逆还原. 向电解液中通入CO₂后,在-1.3 V下的还原峰变得不可逆,且其峰电流从0.48 mA·cm^-2增大到0.55 mA·cm^-2. 在质子源（CH₃OH）存在的条件下,该还原峰电流可继续增大到0.72 mA·cm^-2. 该研究结果表明,Ni(dpim)₂Cl₂配合物对CO₂还原具有良好的电催化性能,且其电催化还原过程符合ECE机理. 在-1.3 V下恒电位电解得到的还原产物主要为CO,催化转换频率（Turnover of Frenquency, TOF）为0.17 s^-1.     

氯化钌氨作前驱体制备高活性的氨合成催化剂

以氯化钌和水合肼反应制备了新型的氧化钌氨前驱体Ru(NH3)5Cl3.透射电镜和CO化学吸附结果表明,由Ru(NH3)5Cl3前驱体制备的活性炭(AC)负载的RuN/AC催化剂中.钌纳米粒子分散度高,粒径分布均匀.与以氯化钌为前驱体制备的Ru/AC催化剂相比,RuN/AC催化剂具有更高的氨合成活性,在10 MPa和10 000 h-1条件下活性增幅超过10%.     

Ru上有氧条件下氨分解的动力学研究

IthasbeenshownthatRuisvalidforthesyn thesisanddecompositionofammonia[1,2 ] .FurtherstudyofammoniaadsorptionanditsdecompositionproductsdesorptiononRuwillbeimportant .Previ ousstudiesofammoniaadsorptiononRumainlyfo cusedontheammoniasynthesisandhydrogenpro ductionintheabsenceofoxygen[3] ,onlyafewinves tigationsonammoniadecompositioninthepresenceofoxygenhavebeenreported[4 ,5] ,andtheeffectofad sorbedoxygenontheratesofammoniadecompositionandproductformationonRuarestillnotwellunder stood .Inthispa…     

Large-Scale and Facile Preparation of Pure Ammonia Borane through Displacement Reactions

Ammonia borane (AB) is the most widely studied hydride for hydrogen storage in addition to being a useful reducing agent. Attempts to synthesize pure AB through simple displacement reactions date back to the 1960s; but have been thwarted by the formation of the diammoniate of diborane (DADB), an ionic byproduct. Based on our recent characterization of the formation mechanism of DADB, we have developed a large-scale synthesis of pure AB by both increasing the basicity of the Lewis base of the borane carrier and using a nonpolar solvent to limit the formation of an intermediate, the ammonia diborane (AaDB). Conditions were optimized for the preparation of pure AB by two displacement reactions, either ammonia with dimethylsulfide borane or ammonia with dimethylaniline borane in toluene at room temperature. These procedures are also suitable for preparation of other amine boranes which had the same problem of forming ionic byproducts during displacement reactions.     

Experimental and computational study of the formation mechanism of the diammoniate of diborane: the role of dihydrogen bonds

The mechanism of formation of ammonia borane (NH(3)BH(3), AB) and the diammoniate of diborane ([H(2)B(NH(3))(2)][BH(4)], DADB) in the reaction between NH(3) and THF·BH(3) was explored experimentally and computationally. Ammonia diborane (NH(3)BH(2)(μ-H)BH(3), AaDB), a long-sought intermediate proposed for the formation of DADB, was directly observed in the reaction using (11)B NMR spectroscopy. The results indicate that dihydrogen bonds between the initially formed AB and AaDB accelerate the formation of DADB in competition with the formation of AB.     

Liquefaction of solid-state BH3NH3 by gaseous NH3

This paper reports for the first time that under ammonia atmosphere, ammonia borane (AB) reversibly absorbs up to at least 6 equiv of NH(3), forming liquid AB(NH(3))(n) (n = 1-6) complexes at 0 °C. Reasonable structures for AB(NH(3))(n) were identified via density functional theory calculations, which indicate that the strong classical hydrogen bond formed between the lone pair of NH(3) and the -NH(3) of AB is the driving force for the absorption of ammonia by AB. By use of the van't Hoff equation, the enthalpy change (ΔH) for AB to absorb one NH(3) was determined to be -2.24 kcal/mol, which is in good agreement with the theoretical calculations. Other organic amines were screened to further confirm the role of the N lone pair; only 1,4-diazabicyclo[2.2.2]octane (DABCO) formed a stable adduct, which X-ray structural analysis showed was the DABCO-BH(3) species. Finally, Raman spectra of AB(NH(3))(n) were collected, and its unique spectral features are also discussed.     

Power‐Law Kinetic Models for Synthesis of Ammonia Borane

In the past few years, there have been increasing numbers of studies for the production and dehydrogenation of ammonia borane (NH₃BH₃, AB), which has become a significant hydrogen storage material. However, kinetic model studies based on the synthesis of AB in the literature have not been encountered, though there are many kinetic modeling studies on dehydrogenation of AB (Akbayrak et al., Appl Catal B 2016, 198, 162–170; Choi et al., Phys Chem Chem Phys 2014, 16(17), 7959–7968; Esteruelas et al., Inorg Chem 2016, 55(14), 7176–7181; Park et al., Int J Hydrogen Energy 2015, 40(46), 16316–16322; Rakap, Appl Catal B 2015, 163, 129–134; Tonbul et al., Int J Hydrogen Energy 2016, 41(26), 11154–11162; Zhang et al., Int J Hydrogen Energy 2016, 41(39), 17208–17215). The paper describes the development of a kinetic model for synthesis of ammonia borane by using borohydride (NaBH₄) and ammonium salt (NH₄)₂SO₄. The synthesis of AB experiments was carried out at different temperature ranges between 25 and 50°C, different inlet molar ratios (NaBH₄/(NH₄)₂SO₄ = 1–4), and different molarities with respect to NaBH₄ (0.11–0.67 M NaBH₄). After the parametric experiments were conducted, empirical power law was evaluated for the synthesis reaction. The power‐law model represented the trends of the kinetics of the synthesis reaction and was reproduced as .     

Large‐Scale and Facile Preparation of Pure Ammonia Borane through Displacement Reactions

Ammonia borane (AB) is the most widely studied hydride for hydrogen storage in addition to being a useful reducing agent. Attempts to synthesize pure AB through simple displacement reactions date back to the 1960s; but have been thwarted by the formation of the diammoniate of diborane (DADB), an ionic byproduct. Based on our recent characterization of the formation mechanism of DADB, we have developed a large‐scale synthesis of pure AB by both increasing the basicity of the Lewis base of the borane carrier and using a nonpolar solvent to limit the formation of an intermediate, the ammonia diborane (AaDB). Conditions were optimized for the preparation of pure AB by two displacement reactions, either ammonia with dimethylsulfide borane or ammonia with dimethylaniline borane in toluene at room temperature. These procedures are also suitable for preparation of other amine boranes which had the same problem of forming ionic byproducts during displacement reactions.     

不同MgO担体对Ba-Ru/MgO氨合成催化剂物化性质和反应性能的影响

采用不同沉淀剂制备了MgO材料,以其为载体制备了Ba-Ru/MgO氨合成催化剂,考察了沉淀剂种类和BaO助剂对其氨合成性能的影响.通过X射线衍射(XRD)、N2物理吸附、X射线荧光光谱(XRF)、透射电镜(TEM)、H2程序升温还原(H2-TPR)、CO2程序升温脱附(CO2-TPD)、H2程序升温脱附(H2-TPD)和N2程序升温脱附(N2-TPD)表征手段,对不同沉淀剂影响Ba-Ru/MgO催化剂氨合成性能的原因进行了探索.结果表明:采用(NH4)2CO3作沉淀剂制备的Ba-Ru/MgO催化剂表面Ru物种易于在低温下还原,催化剂表面在低温区具有较多数量的弱碱性吸附位,在450℃、5.0 MPa和5 000 h-1条件下,由(NH4)2CO3做沉淀剂制备的Ba-Ru/MgO催化剂活性最高,出口氨浓度为3.74%.BaO助剂的加入大大减少了Ba-Ru/MgO催化剂表面吸附氢的数量,增大表面脱附氮的数量,从而易于N2解离吸附,提高氨合成反应速率.     

Formation of Graphene Oxide Nanocomposites from Carbon Dioxide Using Ammonia Borane

To efficiently recycle CO(2) to economically viable products such as liquid fuels and carbon nanomaterials, the reactivity of CO(2) is required to be fully understood. We have investigated the reaction of CO(2) with ammonia borane (AB), both molecules being able to function as either an acid or a base, to obtain more insights into the amphoteric activity of CO(2). In the present work, we demonstrate that CO(2) can be converted to graphene oxide (GO) using AB at moderate conditions. The conversion consists of two consecutive steps: CO(2) fixation (CO(2) pressure < 3 MPa and temperature < 100 °C) and graphenization (600-750 °C under 0.1 MPa of N(2)). The first step generates a solid compound that contains methoxy (OCH(3)), formate (HCOO) and aliphatic groups while the second graphenization is the pyrolysis of the solid compound to produce graphene oxide-boron oxide nanocomposites, which have been confirmed by micro-Raman spectroscopy, solid state (13)C and (11)B magic angle spinning-nuclear magnetic resonance (MAS-NMR), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Our observations also show that the mass of solid product in CO(2) fixation process and raw graphene oxide nanocomposites is twice and 1.2 times that of AB initially charged, respectively. The formation of aliphatic groups without using metal-containing compounds at mild conditions is of great interest to the synthesis of various organic products starting from CO(2.).     

In situ solid state 11B MAS-NMR studies of the thermal decomposition of ammonia borane: mechanistic studies of the hydrogen release pathways from a solid state hydrogen storage material

The mechanism of hydrogen release from solid state ammonia borane (AB) has been investigated via in situ solid state (11)B and (11)B{(1)H} MAS-NMR techniques in external fields of 7.1 T and 18.8 T at a decomposition temperature of 88 degrees C, well below the reported melting point. The decomposition of AB is well described by an induction, nucleation and growth mechanistic pathway. During the induction period, little hydrogen is released from AB; however, a new species identified as a mobile phase of AB is observed in the (11)B NMR spectra. Subsequent to induction, at reaction times when hydrogen is initially being released, three additional species are observed: the diammoniate of diborane (DADB), [(NH(3))(2)BH(2)](+)[BH(4)](-), and two BH(2)N(2) species believed to be the linear (NH(3)BH(2)NH(2)BH(3)) and cyclic dimer (NH(2)BH(2))(2) of aminoborane. At longer reaction times the sharper features are replaced by broad, structureless peaks of a complex polymeric aminoborane (PAB) containing both BH(2)N(2) and BHN(3) species. The following mechanistic model for the induction, nucleation and growth for AB decomposition leading to formation of hydrogen is proposed: (i) an induction period that yields a mobile phase of AB caused by disruption of the dihydrogen bonds; (ii) nucleation that yields reactive DADB from the mobile AB; and (iii) growth that includes a bimolecular reaction between DADB and AB to release the stored hydrogen.