Structural relationships between dicopper diacetylide (Cu-C≡C-C≡C-Cu) and dicopper acetylide (Cu-C≡C-Cu)

Dicopper diacetylide Cu-C≡C-C≡C-Cu, prepared from butadiyne has been studied by FT-IR spectroscopy in comparison to dicopper acetylide Cu-C≡C-Cu. Upon ageing by exposure to air at room temperature, Cu-C≡C-Cu has been transformed into Cu-C≡C-C≡C-Cu as demonstrated by FT-IR spectroscopy and this compound is further transformed on standing in air. A special kind of solid state oxidative coupling reaction occurs so that polyynes chains are formed in these aged solids. It is shown that the FT-IR spectrum of copper acetylide prepared from ammonia solutions of Cu⁺ and Cu²⁺ ions is comparable to that of air oxidized Cu-C≡C-Cu (and Cu-C≡C-C≡C-Cu) prepared exclusively from Cu⁺ ions in presence of a reducing agent demonstrating that Cu²⁺ ions display the same oxidizing effect as oxygen causing coupling reactions in solution and producing Cu-C≡C-C≡C-Cu.Cu-C≡C-Cu oxidized at 60–70°C with CuCl₂ produces a product which could be formulated as Cu(C≡C)₂₀Cu; FT-IR absorption at 1950 cm⁻¹ could suggest the presence of cumulenic carbon chain although acetylenic carbon chains cannot be excluded completely.     

“A-C≡C-TTF-C≡C-A”型四硫富瓦烯衍生物的合成与性质研究

四硫富瓦烯及其衍生物是性能优良的电子给体.本文利用Sonogashira反应将吡啶基团连接在四硫富瓦烯单元上,合成了"A-C≡C-TTF-C≡C-A"型四硫富瓦烯共轭体系衍生物4,4′(5′)-二-(4-吡啶乙炔基)-四硫富瓦烯(TTF4N).吸收光谱、电化学和Pb2+配位键合研究表明,三键作为桥基能够有效实现分子内的电荷转移.金属Pb2+离子与吡啶基团的配位能够引起TTF4N的吸收光谱、核磁氢谱和电化学性质的显著变化.     

PbCNN: A molecule containing Pb≡C bonding

In order to predict potential molecules with Pb≡C bonding, we investigated the potential energy sur-face of a tetra-atomic system [PbCN2] at the CCSD(T)//B3LYP level. We found that the linear isomer PbCNN possesses good thermodynamic and kinetic stability. The combined molecular orbital analysis, hydrogenation heat, bond energy and bond dissociation energy all proved that PbCNN is composed of Pb≡ C triple bonding.     

PbCNN:一个包含Pb≡C键的分子

为了预测一种含有Pb≡C三键的新型分子,在CCSD(T)//B3LYP方法下研究了四原子分子[PbCN2]的势能面,发现线型异构体PbCNN具有良好的热力学和动力学稳定性.分子轨道分析,加氢热,键能及键解离能分析均表明该异构体包含Pb≡C三键.     

PbCNN：一个包含Pb≡C键的分子

为了预测一种含有Pb≡C三键的新型分子,在CCSD（T）//B3LYP方法下研究了四原子分子[PbCN2]的势能面,发现线型异构体PbCNN具有良好的热力学和动力学稳定性．分子轨道分析,加氢热,键能及键解离能分析均表明该异构体包含Pb≡C三键．     

Reaction of the Hexa-1,3,5-triyne Me3SiC≡CC≡CC≡CSiMe3 with Ru4(CO)13(μ 3-PPh): Parallels with the Chemistry of Alkynes and Diynes

Reaction of Ru₄(CO)₁₃(₃-PPh) (1) with the 1,3,5-hexatriyne Me₃SiCCCCC CSiMe₃ under mild thermal conditions affords initially Ru₄(CO)₁₀(-CO)₂{₄-¹,¹,²-P(Ph)C(CCSiMe₃)C(CCSiMe₃) (2), via the facile formation of a P–C bond in a manner similar to that demonstrated previously with alkynes and diynes. The 62-CVE cluster 2 readily decarbonylates to give crystallographically characterised Ru₄(CO)₁₀(-CO)(₄-PPh){₄-¹,¹,²,²-Me₃SiCCC₂CCSiMe₃} (3). Attempts to further incorporate the pendant alkyne moieties in 3 into the Ru₄ coordination environment were partially successful with Ru₄(CO)₁₀(₄-PPh)(₄-¹,¹,³,³-RC₄R') (4, R/R'=SiMe₃/CCSiMe₃) being formed as a minor product together with the unusual toluene coordinated species Ru₄(CO)₇(⁶-C₆H₅Me)(₄-PPh)(₄-¹,¹,³,³-Me₃SiC₄CCSiMe₄) (5). Cluster 3 reacts with an excess of Me₃SiCCCCCCSiMe₃ to give the open chain cluster Ru₄(CO)₉(₃-PPh){₄-²,²,⁴,⁴,-C₄(CCSiMe₃)(SiMe₃)C₄(CCSiMe₃)₃} (6).     

Vibrational solvatochromism and electrochromism of infrared probe molecules containing C≡O, C≡N, C=O, or C-F vibrational chromophore

Solvatochromic vibrational frequency shifts of a few different infrared (IR) probe molecules have been studied by carrying out quantum chemistry calculations for a number of their water clusters. We are particularly focused on the vibrational solvatochromic and electrochromic effects on the CO, CN, and CF stretch modes in carbon monoxide, acetone, 4-cyanopyridine, p-tolunitrile, fluorobenzene, and 3-fluoropyridine. Using multiple interaction site antenna model, we show that their solvatochromic vibrational frequency shifts can be successfully described by considering spatially nonuniform electrostatic potential generated by the surrounding water molecules. It turns out that the CO and CF stretch mode frequencies are approximately proportional to the solvent electric field projected onto the bond axes, whereas the vibrational frequencies of the nitrile stretch mode in 4-cyanopyridine and p-tolunitrile are not. Consequently, it is confirmed that the vibrational Stark tuning rates of the CO and CF stretching modes can be directly used to describe their solvatochromic frequency shifts in condensed phases. However, the nitrile stretch mode frequency shift induced by solvent electrostatic potential appears to be more complicated than its electrochromic phenomenon. To examine the validity of the distributed interaction site model for solvatochromic frequency shifts of these vibrational chromophores, we thus calculated the vibrational Stark tuning rates of the CO, CN, and CF stretch modes and found that they are in good agreement with the experimental results found in literatures. This confirms that a collection of properly chosen distributed interaction sites can be an excellent electric antenna sensing local electrostatics that affects on vibrational frequencies of IR probe modes.     

Synthesis and characterization of stable osmafuran starting from HC≡CCH(OH)C≡CH and OsHCl(CO)(PPh3)3

This paper presents a new convenient route to prepare osmafuran starting from readily accessible HC≡CCH(OH)C≡CH and OsHCl(CO)(PPh₃)₃. Treatment of a solution of OsHCl(CO)(PPh₃)₃ in dichloromethane with HC≡CCH(OH)C≡CH, followed by the addition of acetic acid, produced osmafuran [Os(CHC(PPh₃)CO(CH₂CH₃))Cl(CO)(PPh₃)₂]Cl (2). 2 has been isolated in good yield and fully characterized. ¹H and ¹³C NMR spectra show the characteristic downfield chemical shifts of the ring hydrogen and carbon atoms. NMR and X-ray diffraction data provide strong evidence for the aromatic nature of 2. Probably due to the effect of the phosphonium substituent, 2 exhibits remarkable thermal stability, air stability and lower reactivity.

     

POLYMERIZATION OF p-DIETHYNYLBENZENE INITIATED BY Ni(C≡CC_6H_4C≡CH)_2(PPH_3)_2

Homogeneous polymerization of p-diethynylbenzene initiated by nickel acetylide Ni(C ≡ C C_6H_4 C ≡ CH)_2(PPh_3)_2has been investigated in terms of different solvents, addition agents, atmosphere gases, catalyst concentrations, monomerconcentrations and polymerization temperatures. The yield and catalytic efficiency approach 88% and 11. 1 kg polymer/molNi, respectively, under the optimum conditions: [cat] = 0.01 mol/L, [M] = 1.0 mol/L, NEt_3/cat (mol ratio) = 3～5, 1,4-dioxane/toluene (volume ratio) = 1 and T = 25℃ for 5 h. The polymerization rate equation can be expressed as R_p =k_p[M][cat]~2, where k_p= 0.47 L~2. mol~(-2)·S~(-1) (25℃). The overall polymerization activation energy was found to be203 kJ·mol~(-1). Poly(p-diethynylbenzene) so obtained is soluble in THF, CHCl_3 and toluene with weight-average molecularweights as high as 27, 100 and a rich-trans extended π-conjugated polyene chain structure with pendent groups ofp-C_6H_4C≡CH.     

Zwitterionic [(H3NCH2C≡CC≡CCH2NH3)]Cu2Cl4 π-Complex: Template Synthesis and Crystal Structure

Crystals of the [(H₃NCH₂CCCCCH₂NH₃)]Cu₂Cl₄ -complex, formed in the oxidative dimerization of propargylammonium cations, were obtained by ac electrochemical synthesis from CuCl₂ · 2H₂O and propargylammonium chloride ([CCCH₂NH₃]Cl) and studied by X-ray diffraction analysis (DARCh automated diffractometer, MoK radiation, /2 scan mode; 2275 reflections with F 4(F), R = 0.048). Crystals are monoclinic: space group B2/b, a = 19.591(6) Å, b = 7.299(3) Å, c = 8.636(3) Å, = 106.83(3)°, Z = 4. The structure consists of individual [(H₃NCH₂CCCCCH₂NH₃)]Cu₂Cl₄ moietes united through the elongated Cu···Cl contacts (2.827(5) Å) into chains oriented along the [010] direction. The bond of the centrosymmetric propargylammonium dimer is -coordintated by copper(I) atom and is elongated to 1.227(6) Å.     

Pentavalent Neptunyl ([O≡Np≡O]<Superscript>+</Superscript>) Cation–Cation Interactions in Aqueous/Polar Organic Mixed-Solvent Media

Bonding interactions between polyvalent cations and oxo-anions are well known and characterized by predictably favorable Gibbs energies in solution-phase coordination chemistry. In contrast, interactions between ions of like charge are generally expected to be repulsive and strongly influenced by cation solvation. An exception to this instinctive rule is found in the existence of complexes resulting from interactions of pentavalent actinyl cations ([O≡An≡O]⁺) with selected polyvalent cations. Such cation–cation complexes have been known to exist since the 1960s, when they were first reported by Sullivan and co-workers. The weak actinyl cation–cation complex, resulting from a bonding interaction between a pentavalent linear dioxo actinyl cation donor and hexavalent actinyl or trivalent/tetravalent metal cation acceptor, has been most commonly seen in media in which water activities are reduced, principally highly-salted aqueous media. Such interactions of pentavalent actinides are of relevance in ongoing research that focuses on advanced nuclear fuel processing systems based on the upper oxidation states of americium. This investigation focuses on exploring the thermodynamic stability of complexes between selected highly-charged metal cations (Al³⁺, Sc³⁺, Cr³⁺, Fe³⁺, In³⁺ and \( {\text{UO}}_{2}^{2 + } \)) and the pentavalent neptunyl cation (\( {\text{NpO}}_{2}^{ + } \), whose coordination chemistry is similar to that of \( {\text{AmO}}_{2}^{ + } \) while exhibiting significantly greater oxidation state stability) in aqueous–polar organic mixed-solvents. The Gibbs energies for the cation–cation complexation reactions are correlated with general features of electrostatic bonding models; the \( {\text{NpO}}_{2}^{ + } \cdot {\text{Cr}}^{3 + } \) complex exhibits unexpectedly strong interactions that may indicate significant covalency in the cation–cation bonding interaction.     

Triply bonded stannaacetylene (RC≡SnR): theoretical designs and characterization

The effect of substitution on the potential energy surfaces of RC≡SnR (R = F, H, OH, CH(3), SiH(3), Tbt, Ar*, SiMe(SitBu(3))(2), and SiiPrDis(2)) was explored using density functional theories (B3LYP/LANL2DZdp and B3PW91/Def2-QZVP). Our theoretical investigations indicate that all the triply bonded RC≡SnR molecules prefer to adopt a trans-bent geometry, which is in good agreement with the theoretical model (mode B). In addition, we demonstrate that the stabilities of the RC≡SnR compounds bearing smaller substituents (R = F, H, OH, CH(3), and SiH(3)) decrease in the order R(2)C═Sn: > RC≡SnR > :C═SnR(2). On the other hand, the triply bonded R'C≡SnR' molecules with bulkier substituents (R' = Tbt, Ar*, SiMe(SitBu(3))(2), and SiiPrDis(2)) were found to possess the global minimum on the singlet potential energy surface and are both kinetically and thermodynamically stable. Further, we used the B3LYP computations to predict the stability of stannaacetylene bearing the very bulky phosphine ligand. Our theoretical observations strongly suggest that both the electronic and the steric effects of bulky substituents play an important role in making triply bonded stannaacetylene (RC≡SnR) an intriguing synthetic target.     

类单晶硅结构Si(C≡C―C_6H_4―C≡C)_4新材料的力学与光学性质:第一性原理研究

基于单晶硅中Si的四面体成键特征及对其结构单元的替换修饰,我们设计了一种类单晶硅结构的新材料-C_(40)H_(16)Si_2。通过广泛的第一性原理计算,研究了这类材料的电子性质、力学性质和光学性质。计算结果表明,这种新材料具有好的热力学稳定性和机械稳定性。该材料的禁带宽度为3.32 eV,价带底和导带顶都位于Gamma点,是直接带隙宽禁带半导体材料。该材料的维氏硬度和密度非常小,不到单晶硅的十分之一,是一类低密度的柔性多孔材料。此外,该材料在紫外光区有强的吸收,有望应用于蓝绿光发光二极管。     

Terminal C≡C triple bond hydrogenation using immobilized Wilkinson’s catalyst

In this work, we try to hydrogenate selectively phenylacetylene to styrene and 3-phenylpropyne to allylbenzene using immobilized or pure Wilkinson’s catalyst. The catalyst was immobilized using two approaches—immobilization using ionic exchange and immobilization using covalent bonding. In the first case, the smectite minerals (hectorite and montmorillonite) were used as the supports. In the second case, MCM-41 and SBA-15 were used as the supports. Both types of immobilization were successful and the solid products were characterized. For the covalent bond formation, it was necessary to first modify the surface of the silica material. The modification was carried out using two substances, one adding an amino group to the silica material, and the second adding a phenyl group to the material. The selectivity of hydrogenation of both substances was higher using heterogeneous catalyst in the case of phenylacetylene. In the case of phenylpropyne, no difference in selectivity using Wilkinson’s catalyst in homogeneous or heterogeneous arrangement was observed. The type of immobilization has no influence on either activity or selectivity of catalyst.     

Charge density analysis of 2-methyl-4-nitro-1-phenyl-1H-imidazole-5-carbonitrile: an experimental and theoretical study of C≡N···C≡N interactions

The experimental charge density distribution was determined for 2-methyl-4-nitro-1-phenyl-1H-imidazole-5-carbonitryle, using the Hansen-Coppens multipole model. Free R factor calculations were performed with MoPro software to find optimal restraints for a physically meaningful model. The crystal packing is determined to some extent by weak C-H···O and C-H···N hydrogen bonds but mostly by a lateral electrostatic interaction between antiparallel side-by-side C≡N groups. Electrostatic energy calculations were performed based on the experimental data and are in line with the high-level, explicitly correlated theoretical SCS-RI-MP2-F12 calculations of total energy. The molecular dipole moment and atomic charge values were compared for different experimental and theoretical models, to highlight the dependence of the electrostatic property outputs on the applied restraints. Interesting O···O contacts are also described. The results are compared with two recently investigated nitroimidazole derivatives, namely, 1-(2'-aminophenyl)-2-methyl-4-nitroimidazole and 1-phenyl-4-nitroimidazole.     

重元素多重金属-金属键的新发现:U≡Fe三重键

正自1964年Cotton等人发现[Re_2Cl_8]~(2-)化合物中存在Re―Re四重键以来~1,金属―金属多重键的研究在无机化学、金属有机化学、结构化学和理论化学等领域引起了广泛关注~(2,3),其中包含锕系元素的金属-金属键尤为引人关注。锕系元素的5f、6d、7s和7p轨道能量相差不大,在适当条件下均可以参与化学成键,这使得锕系元素的成键情况比过渡金属要复杂得多。然而涉及锕系元素的实验研究非常困难,到目前为止只有少数实验合成     

Linear Group 13 E≡E Triple Bonds in E2Li62+

The triply bonded heavier main-group compounds have a textbook trans-bent geometry, in contrast to a familiar linear form found for the lightest analogues. Strikingly, the unexpected linear group 13 E≡E triple bonds were herein found in the D_4h-symmetry E₂Li₆²⁺ clusters, and they possess a large barrier (>18.0 kcal/mol) towards the dissociation of Li⁺. The perfectly surrounded Li₄ motifs and two linear coordinated Li atoms strongly suppress the increasing nonbonded electron density of heavier E atoms, making two degenerate π bonds and one multi-center σ bond in linear heavier main-group triple bonds. The surrounding Li₆ motifs not only creates an effective electronic structure to form a linear E≡E triple bond, but the resulting electrostatic interactions account for the highly stable global E₂Li₆²⁺ clusters.     

Selective synthesis of organogold magic clusters Au54(C≡CPh)26

Organogold clusters Au(54)(C(2)Ph)(26) were selectively synthesized by reacting polymer-stabilized Au clusters (1.2 ± 0.2 nm) with excess phenylacetylene in chloroform.     

碳碳偶合反应中间体Li[Cp2Zr(C≡CPh)·(η2∶1,2-PhC2C≡CPh)]的合成和晶体结构

室温下, 用Cp2ZrCl2 与LiC≡CPh反应, 合成了碳碳偶合反应的Zr(Ⅱ)阴离子中间体Li[Cp2Zr(C≡CPh)(η2:1,2-PhC2C≡CPh)]. 用元素分析、核磁共振谱和红外光谱对配合物进行了表征, 配合物的晶体结构分析给出了两个炔烃之间碳碳偶合的证据. 用核磁共振谱初步探讨了合成反应机理.