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1.
采用密度泛函理论的B3LYP泛函对AuCl3催化的2-(1-炔基)-2-烯基酮与亲核试剂反应的机理进行了研究, 得到了反应的最优路径. 结果表明, 整个反应的决速步骤是羟基H转移到AuCl3的配体Cl上, 其活化能为49.3 kJ·mol-1. 通过计算发现, 催化剂AuCl3的配体Cl原子在反应中有重要的作用, 它不仅稳定配合物, 而且直接参与反应, 协助质子的转移, 显著降低质子转移的活化能(由71.5 kJ·mol-1降低到49.3 kJ·mol-1). 另外还讨论了HBF4不能催化此反应的可能原因, 计算结果与实验结果一致.  相似文献   

2.
合成了高氯酸镨和咪唑(C3H4N2), DL-α-丙氨酸(C3H7NO2)混配配合物晶体. 经傅立叶变换红外光谱、化学分析和元素分析确定其组成为[Pr(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3. 使用具有恒温环境的溶解-反应量热计, 以2.0 mol•L-1 HCl为量热溶剂, 在T=(298.150±0.001) K时测定出化学反应PrCl3•6H2O(s)+2C3H7NO2(s)+C3H4N2(s)+3NaClO4(s)=[Pr(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s)+3NaCl(s)+5H2O(1)的标准摩尔反应焓为ΔrHmө=(39.26±0.11) kJ•mol-1. 根据盖斯定律, 计算出配合物的标准摩尔生成焓为ΔfHmө{[Pr(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s), 298.150 K}=(-2424.2±3.3) kJ•mol-1. 采用TG-DTG技术研究了配合物在流动高纯氮气(99.99%)气氛中的非等温热分解动力学, 运用微分法(Achar-Brindley-sharp和Kissinger法)和积分法(Satava-Sestak和Coats-Redfern法)对非等温动力学数据进行分析, 求得分解反应的表观活化能E=108.9 kJ•mol-1, 动力学方程式为dα/dt=2(5.90×108/3)(1-α)[-ln(1-α)]-1exp(-108.9×103/RT).  相似文献   

3.
合成了高氯酸镨和咪唑(C3H4N2), DL-α-丙氨酸(C3H7NO2)混配配合物晶体. 经傅立叶变换红外光谱、化学分析和元素分析确定其组成为[Pr(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3. 使用具有恒温环境的溶解-反应量热计, 以2.0 mol•L-1 HCl为量热溶剂, 在T=(298.150±0.001) K时测定出化学反应PrCl3•6H2O(s)+2C3H7NO2(s)+C3H4N2(s)+3NaClO4(s)=[Pr(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s)+3NaCl(s)+5H2O(1)的标准摩尔反应焓为ΔrHmө=(39.26±0.11) kJ•mol-1. 根据盖斯定律, 计算出配合物的标准摩尔生成焓为ΔfHmө{[Pr(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s), 298.150 K}=(-2424.2±3.3) kJ•mol-1. 采用TG-DTG技术研究了配合物在流动高纯氮气(99.99%)气氛中的非等温热分解动力学, 运用微分法(Achar-Brindley-sharp和Kissinger法)和积分法(Satava-Sestak和Coats-Redfern法)对非等温动力学数据进行分析, 求得分解反应的表观活化能E=108.9 kJ•mol-1, 动力学方程式为dα/dt=2(5.90×108/3)(1-α)[-ln(1-α)]-1exp(-108.9×103/RT).  相似文献   

4.
以磷酸二氢铵、醋酸钴和氢氧化锂为原料, 用低温固相反应合成含Li+的NH4CoPO4前驱体, 再经过高温焙烧合成LiCoPO4粉体. 应用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)和热重-差热分析(TG-DTA)等技术对合成产物进行表征. 结果表明: 焙烧气氛影响中间体的生成, 含Li+的前驱体NH4CoPO4在210-500 °C的空气中发生脱水脱氨反应, 制备过程存在“酸碱共同体”的中间体(CoHPO4·LiCoPO4·Co2(OH)PO4·Li3PO4). 中间体生成反应遵循界面反应幂律机理, 表观活化能约50.0 kJ?mol-1, 过程机理函数为g(x)=(1-α)-1. 中间体继续脱水反应生成LiCoPO4, 平均表观活化能约为54.2 kJ?mol-1. 物系非晶化和晶化过程对中间体的存在没有直接的影响, 高温对中间体的分解产物LiCoPO4和LiCoPO4的晶体生长有利, 在550 °C以上温度中间体可分解得到完整的LiCoPO4晶体.  相似文献   

5.
王树建  李莹  吴迪* 《物理化学学报》2012,28(12):2817-2823
采用二级微扰理论(MP2)量子化学研究方法, 对C2H4-nFn···LiH (n=0, 1, 2)二聚体的结构和π锂键性质进行了分析. 结果表明氟原子的取代改变了乙烯分子的π电子云形状, 从而使二聚体体系中的π锂键发生偏移、伸长和弯曲. 通过与类似的π氢键体系C2H4-nFn···HF (n=0, 1, 2)比较, 发现π锂键在二级弱相互作用的影响下, 发生了明显的弯曲, 表现出弱的方向性. 在CCSD(T)/6-311++G(3df, 3pd)理论水平下, 二聚体的相互作用能强弱顺序为: 33.85 kJ·mol-1 (C2H4-LiH)>27.32 kJ·mol-1 (C2H3F-LiH)>21.34 kJ·mol-1 (cis-C2H2F2-LiH)>20.25 kJ·mol-1 (g-C2H2F2-LiH), 说明氟取代削减了乙烯分子与LiH之间的相互作用.  相似文献   

6.
合成了四氯合锌酸正九烷铵复合物(C9H19NH3)2ZnCl4(s) (C9Zn(s)), 并使用X射线单晶衍射、化学分析以及元素分析确定了其晶体结构和化学组成. 利用其晶体学数据推导了C9Zn(s)的晶格能UPOT=952.94 kJ·mol-1. 在298.15 K下, 利用恒温环境溶解-反应热量计测定了C9Zn(s)在不同质量摩尔浓度下的摩尔溶解焓. 在Pitzer电解质溶液理论基础上确定了C9Zn(s)的无限稀释摩尔溶解焓ΔsΗm=20.09 kJ·mol-1, 以及Pitzer焓参数组合(4βC9H19NH3,Cl(0)L+2βZn,Cl(0)LC9H19NH3,ZnL)和(2βC9H19NH3,Cl(1)LZn,Cl(1)L)的值.  相似文献   

7.
提出了两个稳定的团簇B12Sc4和B12Ti4, 基于理论计算, 研究了它们的结构与储氢性质. 结果发现, 在这两个稳定的团簇中, 过渡金属原子不会聚合在一起而影响它们对氢气的吸附. B12Sc4最多可以吸附12个氢分子, 达到7.25% (质量分数)的储氢量. 它的平均每氢分子吸附能量为10.5 kJ·mol-1. B12Ti4最多只能吸附8个氢分子, 储氢量为4.78%. 但平均每氢分子吸附能量可达50.2 kJ·mol-1. 进一步计算表明, 即使在77 K,也需要很高的氢气压力才能使12个氢分子都吸附到B12Sc4上. 电子结构分析表明, B12Ti4-nH2吸附结构中的Kubas作用要大于相应B12Sc4-nH2结构中的Kubas作用.  相似文献   

8.
采用双水平直接动力学方法对C2H3与CH3F氢抽提反应进行了研究. 在QCISD(T)/6-311++G(d, p)//B3LYP/6-311G(d, p)水平上, 计算的三个反应通道R1、R2和R3的能垒(ΔE)分别为43.2、43.9和44.1 kJ·mol-1, 反应热为-38.2 kJ·mol-1. 此外, 利用传统过渡态理论(TST)、正则变分过渡态理论(CVT)和包含小曲率隧道效应(SCT)的CVT, 分别计算了200-3000 K温度范围内反应的速率常数kTST、kCVT和kCVT/SCT. 结果表明: (1) 三个氢抽提反应通道的速率常数随温度的增加而增大, 其中变分效应的影响可以忽略, 隧道效应则在低温段影响显著; (2) R1反应是主反应通道, 但随着温度的升高, R2反应的竞争力增大, 而R3反应对总速率常数的影响很小.  相似文献   

9.
采用密度泛函理论(DFT)研究了NH3/KI、KI及无催化剂条件下, CO2与环氧丙烷(PO)合成碳酸丙烯酯(PC)的反应机理. 在B3LYP/6-311++G**基组水平上(I采用MIDIX基组)优化了反应过程中的反应物、中间体、过渡态和产物, 通过振动分析及内禀反应坐标(IRC)确定中间体和过渡态的真实性. 同时, 在相同基组水平应用自然键轨道(NBO)理论和分子中的原子(AIM)理论分析了这些化合物的轨道间相互作用和成键特征. 研究结果表明: 在无催化剂条件下非协同反应通道PO+CO2→M0a→TS0c→M0c→TS0c′→PC为最有利通道, 其活化能为200.65 kJ·mol-1; KI催化下活化能降低至187.40 kJ·mol-1, 反应速率较小; 在KI/NH3协同催化下, 除KI的催化作用外, NH3中的氢原子还能与CO2或PO中的氧原子形成氢键, 活化反应, 活化能降低至154.64 kJ·mol-1, 大幅度提高了PO与CO2环合生成产物PC的反应速率, 理论计算与实验结果一致.  相似文献   

10.
复盐K2Zn(IO3)4·2H2O的热化学研究   总被引:3,自引:0,他引:3  
The standard enthalpy of formation (ΔfH?m[K2Zn(IO3)4·2H2O,s,298.2K]=-2210.68 kJ·mol-1) of a double salt K2Zn(IO3)4·2H相似文献   

11.
以TiF3和Ti(OBu-n)4为催化剂, 研究了Ti离子掺杂对MgH2和Mg2NiH4放氢性能的影响. 结果表明, 未掺杂的MgH2起始放氢温度为420 ℃, 掺杂TiF3和Ti(OBu-n)4后分别降低到360和410 ℃; Mg2NiH4在掺杂TiF3后放氢温度由230 ℃降低到220 ℃, 而掺杂Ti(OBu-n)4后没有变化. 可见无论对MgH2或Mg2NiH4, 在降低放氢温度方面TiF3都明显优于Ti(OBu-n)4. 另外, 研究还发现, TiF3掺杂对MgH2放氢动力学有显著的提高, 但对Mg2NiH4没有明显的提高. 结合XRD和FTIR的测试分析, 我们认为: 催化作用很大程度上取决于氢化物自身的晶体结构和催化剂的电子结构; 降低氢化物放氢温度和提高动力学性能的原因是催化剂与氢化物之间的相互作用削弱了氢化物中Mg—H或Ni—H键, 使得活泼的H…H原子对容易形成, 从而有利于H2的释出.  相似文献   

12.
There has been speculations on the structures of TiF4 polymeric complexes {TiF4L}n (L = molecular donor) for several decades, however no structurally characterized examples have been reported. In this work the complex {TiF4(PhCN)}3 was isolated from a solution of TiF4 in PhCN (donor number DN = 11.9 kcal mol−1) as well as from the mixtures PhCN/CH2Cl2 and PhCN/toluene and characterized by X-ray, IR, NMR, EI-MS. The structure of the complex {TiF4(PhCN)}3 can be regarded as formed by combining three face-TiF3(PhCN)(μ-F) units, containing octahedrally coordinated titanium centers surrounded by three terminal fluorine atoms on the face of the octahedron and the bridging fluorine atoms in cis-positions with respect to each other. The structure of {TiF4(PhCN)}3 represents the first example of a trimeric pseudo pentahalide MX4L (M = Ti, Zr, X = halogen, D = ligand), a class of potentially interesting Lewis acids. The characterization of {TiF4(PhCN)}3 by 19F NMR revealed that in solution it dissociated to a mixture of [TiF3(PhCN)3]+, TiF4(PhCN)2 and oligomers including [Ti4F18]2− and {TiF4(PhCN)}n. The existence of oligomeric complexes containing face-{TiF3(PhCN)3−n(μ-F)n} (n = 1-3) fragments was established by one- and two-dimensional variable temperature 19F NMR. In contrast, TiF4 has a low solubility in SO2, because the donor strength of SO2 (DN = 6.5 ± 2.2 kcal mol−1) is too weak to fully convert polymeric TiF4 into soluble TiF4-SO2 donor-acceptor adducts. TiF4 and MeCN (DN = 14.1 kcal mol−1) formed only the molecular complex TiF4(MeCN)2, characterized by preliminary X-ray structure, IR and EI-MS. Thus mononuclear donor-acceptor complexes TiF4L2 can only be isolated from MeCN and stronger basic solvents.  相似文献   

13.
Metal Tetrahydroborates and Tetrahydroboratometallates. VIII. Preparation and Properties of Dimeric Halogenotitanium(III) Bis(tetrahydroborates) [XTi(BH4)2]2 Chlorotitanium(III)bis(tetrahydroborate) is produced besides Ti(BH4)3 in the reaction of TiCl4 vapour with solid LiBH4. It forms in 72% yield by using n-pentane as reaction medium. BrTi(BH4)2 and ITi(BH4)2 were prepared similarly. All these compounds are dimerized via halogen bridges. The bridge opens by addition of tetrahydrofurane to ClTi(BH4)2 with disproportionation to yield Ti(BH4)3 · nOC4H8 and TiCl3 · mOC4H8 contrary to diethylether. The ir, 11B-nmr and electronic spectra of the halogenotitanium(III) bis(tetrahydroborates) are discussed.  相似文献   

14.
On the Existence of the Compound K2TiOF4: Pyrohydrolytic Degradation of K2TiF6 and Thermochemical Behaviour of K2Ti(O2)F4 · H2O In an attempt to prepare K2TiOF4 we used the following three ways; solid-state reaction of K2TiF6, TiO2, and KF, pyrohydrolysis of K2TiF6 at 450 and 550°C, and thermal decomposition of K2Ti(O2)F4 · H2O. In each case the reaction products were mixtures of several compounds, always containing the kryolith-phase K2+xTiOxF6?x and TiO2. At 130°C K2Ti(O2)F4 · H2O forms K2Ti(O2)F4 by loss of H2O, and at 230°C the peroxogroup decomposes, yielding K2TiOF4 as main product. K2TiOF4 crystallizes tetragonally with the following lattice parameters: a = 769.7(1) and c = 1153.9(2)pm. The i.r. spectrum shows an absorption band at 810 cm?1, pointing to infinite chains of ? Ti? O? Ti? O? .  相似文献   

15.
The first Al‐based amidoborane Na[Al(NH2BH3)4] was obtained through a mechanochemical treatment of the NaAlH4–4 AB (AB=NH3BH3) composite releasing 4.5 wt % of pure hydrogen. The same amidoborane was also produced upon heating the composite at 70 °C. The crystal structure of Na[Al(NH2BH3)4], elucidated from synchrotron X‐ray powder diffraction and confirmed by DFT calculations, contains the previously unknown tetrahedral ion [Al(NH2BH3)4]?, with every NH2BH3? ligand coordinated to aluminum through nitrogen atoms. Combination of complex and chemical hydrides in the same compound was possible due to both the lower stability of the Al?H bonds compared to the B?H ones in borohydride, and due to the strong Lewis acidity of Al3+. According to the thermogravimetric analysis–differential scanning calorimetry–mass spectrometry (TGA–DSC–MS) studies, Na[Al(NH2BH3)4] releases in two steps 9 wt % of pure hydrogen. As a result of this decomposition, which was also supported by volumetric studies, the formation of NaBH4 and amorphous product(s) of the surmised composition AlN4B3H(0–3.6) were observed. Furthermore, volumetric experiments have also shown that the final residue can reversibly absorb about 27 % of the released hydrogen at 250 °C and p(H2)=150 bar. Hydrogen re‐absorption does not regenerate neither Na[Al(NH2BH3)4] nor starting materials, NaAlH4 and AB, but rather occurs within amorphous product(s). Detailed studies of the latter one(s) can open an avenue for a new family of reversible hydrogen storage materials. Finally, the NaAlH4–4 AB composite might become a starting point towards a new series of aluminum‐based tetraamidoboranes with improved hydrogen storage properties such as hydrogen storage density, hydrogen purity, and reversibility.  相似文献   

16.
The thermal behaviour of ammonium oxofluorotitanates (NH4)3TiOF5, (NH4)2TiOF4 and NH4TiOF3 was investigated by thermoanalytical, X-ray and IR spectroscopic methods. The first decomposition stages under quasi-isobaric conditions are characterized by the formation of (NH4)2TiF6 and ammonium oxofluorotitanate with the less content of ammonium and fluorine than in the initial compound. The decomposition process is accompanied by the Ti(IV) reducing due to ammonia evolved. The new ammonium oxofluorotitanate of high volatility was isolated and characterized. Ammonium-containing non-stoichiometric titanium oxyfluorides are the final products of thermal decomposition of ammonium oxofluorotitanates.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

17.
Hydrocarbon‐soluble model systems for the calcium–amidoborane–ammine complex Ca(NH2BH3)2 ? (NH3)2 were prepared and structurally characterized. The following complexes were obtained by the reaction of RNH2BH3 (R=H, Me, iPr, DIPP; DIPP=2,6‐diisopropylphenyl) with Ca(DIPP‐nacnac)(NH2) ? (NH3)2 (DIPP‐nacnac=DIPP? NC(Me)CHC(Me)N? DIPP): Ca(DIPP‐nacnac)(NH2BH3) ? (NH3)2, Ca(DIPP‐nacnac)(NH2BH3) ? (NH3)3, Ca(DIPP‐nacnac)[NH(Me)BH3] ? (NH3)2, Ca(DIPP‐nacnac)[NH(iPr)BH3] ? (NH3)2, and Ca(DIPP‐nacnac)[NH(DIPP)BH3] ? NH3. The crystal structure of Ca(DIPP‐nacnac)(NH2BH3) ? (NH3)3 showed a NH2BH3? unit that was fully embedded in a network of BH???HN interactions (range: 1.97(4)–2.39(4) Å) that were mainly found between NH3 ligands and BH3 groups. In addition, there were N? H???C interactions between NH3 ligands and the central carbon atom in the ligand. Solutions of these calcium–amidoborane–ammine complexes in benzene were heated stepwise to 60 °C and thermally decomposed. The following main conclusions can be drawn: 1) Competing protonation of the DIPP‐nacnac anion by NH3 was observed; 2) The NH3 ligands were bound loosely to the Ca2+ ions and were partially eliminated upon heating. Crystal structures of [Ca(DIPP‐nacnac)(NH2BH3) ? (NH3)], Ca(DIPP‐nacnac)(NH2BH3) ? (NH3) ? (THF), and [Ca(DIPP‐nacnac){NH(iPr)BH3}]2 were obtained. 3) Independent of the nature of the substituent R in NH(R)BH3, the formation of H2 was observed at around 50 °C. 4) In all cases, the complex [Ca(DIPP‐nacnac)(NH2)]2 was formed as a major product of thermal decomposition, and its dimeric nature was confirmed by single‐crystal analysis. We proposed that thermal decomposition of calcium–amidoborane–ammine complexes goes through an intermediate calcium–hydride–ammine complex which eliminates hydrogen and [Ca(DIPP‐nacnac)(NH2)]2. It is likely that the formation of metal amides is also an important reaction pathway for the decomposition of metal–amidoborane–ammine complexes in the solid state.  相似文献   

18.
The reaction of zinc halides (ZnCl2, ZnBr2) or Zn(BH4)2 with LiBH4 or NaBH4 in ether or tetrahydrofurane yields LiZn(BH4)3, Li2Zn(BH4)4 or NaZn(BH4)3 respectively. The latter complex is also obtained by the reaction of NaZn(OCH3)3 or Na2Zn(OCH3)4 with diborane. Octakis(tetrahydridoborato)-trizincate K2Zn3(BH4)8 and BaZn3(BH4)8 are formed by treating Zn(BH4)2 with KBH4 or Ba(BH4)2. The 11B-nmr- and ir-spectra of the new complexes are recorded and discussed in terms of double hydrogen bridge bonding of BH4 groups to the central zinc atom.  相似文献   

19.
Mono- and Dinuclear Fluoro Complexes of Titanium (III), Chromium (III), and Iron(III). Syntheses and Structures of (NMe4) (Ti(H2O)4F2)TiF6 · H2O, (NMe4)3Cr2F9, and (NMe4)3Fe2F9 The title compounds have been prepared by reaction of MCl3 (M = Ti, Cr, Fe) with NMe4F in dimethylformamide. (NMe4)3Cr2F9 and (NMe4)3Fe2F9 contain the face-sharing biocathedral M2F93? unit. The M…M distances are 277.1(1) and 289.8(3) pm in (NMe4)3Cr2F9 and (NMe4)Fe2F9, respectively. (NMe4)(Ti(H2O)4F2)TiF6 · H2O contains trans-TiIII(H2O)4F2+ cations and TiIVF62? anions. Crystal data: (NMe4)3Cr2F9: hexagonal, space group P63/m, a = 804.1(3), c = 1857.5(4) pm, Z = 2, 529 reflections, R = 0.049; (NMe4)3Fe2F9: hexagonal, space group P63/m, a = 804.7(5), c = 1 861.6(5) pm, Z = 2, 635 reflections, R = 0,046; (NMe4)(Ti(H2O)4F2)TiF6 · H2O: orthorhombic, space group Pbca, a = 776.9(2), b = 1 616.3(3), c = 2 428.6(7) pm, Z = 8, 2 784 reflections, R = 0,056.  相似文献   

20.
The products resulting from the reaction of TiF4 with Ph2P(O)(CH2)2C(O)Me (L') in CH2Cl2 have been studied by 19F{1H} and 31P{1H} NMR spectroscopy. At a twofold excess of L', solution contains cis-TiF4(L')2 (>90%), trans-TiF4(L')2, and fac-[TiF3L3']+, where L' is coordinated via the P=O group, as well as the dimer [(Ti2F7L'2)2]+, where L' is coordinated through the P=O and C=O groups. An equimolar solution contains dimeric and polynuclear complexes containing moieties with three terminal cis fluorine ions, while the other coordination sites are occupied by the P=O groups and F bridges. At a twofold excess of TiF4, ligand L' coordinates via the P=O and C=O groups and behaves as a bridge along with F ions. Thermodynamic stability of the structures of the TiF4L'2 isomers and the structure of [(µ-F)(µ-L')2(TiF3)2]+ has been calculated.  相似文献   

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