A highly reduced cyanogen ligand derived from cyanide reductive coupling

The synthesis, structure, and spectroscopic features of a bimetallic cyanogen complex obtained from the reductive coupling of cyanide by a niobium(IV) precursor are described, and a mechanism for the coupling reaction is proposed based on DFT calculations.     

Carbon-carbon and carbon-nitrogen coupling reactions catalyzed by palladium nanoparticles derived from a palladium substituted Keggin-type polyoxometalate

Palladium 15-20 nm particles stabilized by a Keggin-type polyoxometalate were prepared by reduction of K(5)PPdW(11)O(39) with H(2). The nanoparticles were shown to be effective catalysts for Suzuki-, Heck-, and Stille-type carbon-carbon coupling and carbon-nitrogen coupling reactions of bromoarenes in aqueous media. Chloroarenes were also reactive in reaction media without solvent. [reaction: see text]     

Vacuum pyrolysis study of graphite-like pyropolymers from 1,4-diphenyl-1-buten-3-yne

1,4-Diphenyl-1-buten-3-yne was metathesis polymerized over NbCl₅- or TaCl₅-based catalysts followed by pyrolysis to obtain graphite-like pyropolymers. The brown metathesis polymer, poly(1,4-diphenyl-1-buten-3-yne), has the structure of fully conjugated backbone and was annealed at 250°C to obtain partially crosslinked polymer which showed 20% increase of carbon residue on pyrolysis over 400°C than the pyrolyzed poly(1,4-diphenyl-1-buten-3-yne) without annealing. The polymers were characterized by GPC, EA, NMR, XPS, TGA, DSC, FT-IR, laser-Raman, x-ray diffraction, and SEM studies. © 1996 John Wiley & Sons, Inc.     

Thermal analysis of phenolic resin based pyropolymers

The formation and thermal behaviour of pyropolymers based on novolak resin synthesized under carefully controlled processing conditions have been studied by various thermoanalytical techniques. A suitable reaction scheme has been proposed for the formation of these pyropolymers. Only a small (3–8%) weight loss has been observed up to 800 °C in static air. DTA curves confirmed multistage exothermic processes predominantly due to two different linkages which control their thermo/thermo-oxidative stability. Hot metal filtration (700 °C) in an inert atmosphere exhibited only negligible weight loss.

---

Zusammenfassung Mittels verschiedener thermoanalytischer Verfahren wurde Bildung und thermisches Verhalten von Pyropolymeren auf Novolackbasis unter streng geregelten Reaktionsbedingungen untersucht. Zur Bildung dieser Pyropolymere wurde ein geeignetes Reaktionsschema entwickelt. In unbewegter Luftatmosphäre kann bis 800 °C nur ein geringer (3–8%) Gewichtsverluft beobachtet werden. Die DTA-Kurven zeigen einen exothermen Mehrstufenprozeß, der hauptsächlich auf zwei verschiedene Verkettungen zurückzuführen ist, welche die thermische/thermisch-oxidative Stabilität bestimmen.

---

. . 800° (3–8%) . , , / - . (700° .

     

Alkyl carbon-nitrogen reductive elimination from platinum(IV)-sulfonamide complexes

Platinum(IV) complexes containing monodentate sulfonamide ligands, fac-(dppbz)PtMe(3)(NHSO(2)R) (dppbz = o-bis(diphenylphosphino)benzene; R = p-C(6)H(4)(CH2)(3)CH(3) (1a), p-C(6)H(4)CH(3) (1b), CH(3) (1c)), have been synthesized and characterized, and their thermal reactivity has been explored. Compounds 1a-c undergo competitive C-N and C-C reductive elimination upon thermolysis to form N-methylsulfonamides and ethane, respectively. Selectivity for either C-N or C-C bond formation can be achieved by altering the reaction conditions. Good yields of the C-N-coupled products were observed when the thermolyses of 1a-c were conducted in benzene-d(6). In contrast, exclusive C-C reductive elimination occurred upon themolysis of 1a,b in nitrobenzene-d(5). When the thermolyses of 1a were performed in the presence of sulfonamide anion NHSO2R- in benzene-d(6), ethane elimination was completely inhibited and C-N reductive elimination products were formed in high yield. Mechanistic studies support a two-step reaction pathway involving initial dissociation of NHSO(2)R(-) from the platinum center, followed by nucleophilic attack of this anion on a methyl group of the resulting five-coordinate platinum(IV) cation to form MeNHSO(2)R and (dppbz)PtMe(2). C-C reductive elimination to form ethane occurs directly from the five-coordinate Pt(IV) cation.     

碳氮二元簇离子的激光产生与碰撞诱导解离研究

以脉冲激光束在高真空中溅射铁氰化钾,产生了各种组成的碳氮原子簇负离子,记录了它们的飞行时间质谱。根据这些簇离子的碰撞诱导解离研究结果,推测了它们的结构,发现它们大都具有超共轭的稳定体系,它们的构型随成簇氮原子数的增加,从一维直链向二维芳环转化。     

Stability of carbon-nitrogen cages in fourfold symmetry

Molecules consisting entirely of nitrogen have been studied extensively for their potential as high-energy density materials (HEDM). Many nitrogen molecules previously studied have low-energy dissociation routes and are therefore too unstable to serve as practical HEDM. However, the incorporation of heteroatoms into a nitrogen structure can have stabilizing effects. Theoretical calculations are carried out on a sequence of high-energy cages with carbon and nitrogen. Density functional theory (B3LYP), perturbation theory (MP2 and MP4), and coupled-cluster theory (CCSD(T)) are used in conjunction with the correlation-consistent basis sets of Dunning. Stability trends as a function of molecule size are calculated and discussed.     

The force fields of cyanogen halides. III. Cyanogen bromide and cyanogen iodine

Following work determining the force fields of FCN and ClCN a related treatment for BrCN and ICN leads to the force fields indicated in Table 1 and giving the agreement with experiment shown by Tables 3, 4 and 5 for BrCN and Tables 7 and 8 for ICN. Table 6 gives the agreement of B₀ values for all isotopic molecules with r_e values for BrCN of 178.611 and 115.767 pm and for ICN of 199.241 and 115.965 pm for the XC and CN bonds, respectively.     

Determination of cyanogen and cyanogen chloride using gas chromatography with a flame ionisation detector

Summary The response of a flame ionisation detector (FID) to cyanogen ((CN)₂) and cyanogen chloride (CNCI) has been studied. The lower limits of detection for (CN)₂ and CNCl were 6×10⁻¹² moles and 2×10⁻¹¹ moles respectively. In a comparative study a thermal conductivity detector gave as its lower limit of detection for both (CN)₂ and CNCl 4×10⁻¹¹ moles. Both detectors showed excellent linearity over the range 0 to 10 micromoles. The ratio of the gradients of the FID calibrations (CN)₂/CNCI were found to be approximately two suggesting the response depended on the cyanide group. The response and stability of the FID was investigated as a function of air and hydrogen flow-rates. The response increased with increasing air flow-rate for both (CN)₂ and CNCI up to 300cm³min⁻¹, thereafter no significant increase was observed. On raising the hydrogen flow from 10 to 25cm³min⁻¹ only a slight increase in the sensitivity of the FID towards both (CN)₂ and CNCI was observed. At higher flow rates the response for (CN)₂ increased markedly whereas at the same flow rates the response for CNCI increased only slightly.     

Conducting composites from EPDM–EVA blends

The effect of ethylidene norbornene (ENB) content of ethylene propylene aiene rubber (EPDM) and vinyl acetate (VA) content of ethylene vinyl acetate copolymer (EVA), as well as the blending sequence, on the conductivity of composites based on EPDM–EVA–carbon black have been studied. Black master batches show a lower extent of cure than the preblended system followed by black addition. EPDM having a high ENB content shows higher conductivity under ambient conditions. Preblended systems give rise to higher conductivity in the case of low-ENB content EPDM. But for high-ENB content EPDM, the blending of black master batches imparts high conductivity. Two types of conduction are observed in this case and the transition temperature depends on the VA content of EVA. It appears that there exists a correlation between activation energy of curing and that of conduction.     

导电聚合物

导电聚合物是20世纪70年代发展起来的一个研究领域,因其诱人的应用前景受到广泛重视,本文介绍了导电聚合物的发展和发展历史,综述了导电聚合物的结构和掺杂特征,制造方法,电导和电化学特性及其本征态共轭聚合物的光电特性,对导电聚合物当前的研究热点和应用前景进行了讨论。     

On the anionic polymerization of cyanogen

The reaction of anionic initiators with cyanogen was investigated by ultraviolet, visible, and infrared spectroscopy. It is argued that the reaction proceeds via formation of an analog of the heterocyclic anion C₇N₇? previously known from the reaction of KCN with (CN)₂. The analytical results and spectra of the final black product were indicative of the possible formation of open-structured C₇N₇? dimers. A molecular model of the dimer suggests why the polymerization might terminate at the dimer stage. The pyrolysis of the cyclic acid HC₇N₇ was studied with the aim of determining the structure and mechanism of the formation of the resulting black product. It is suggested that this thermally induced polymerization reaction probably proceeds via formation of azomethine-type intermolecular crosslinks and may serve as a model for the investigation of the mechanism of nitrile polymerization in pyrolyzed acrylonitrile polymers.     

Heterocycles derived from dichlorothiophene

A number of new, air-stable heterocycles have been synthesized which contain 2,5-dichlorothiophene groups as the structure-forming units with sulphur, selenium, tellurium, phosphorus, arsenic, antimony, bismuth, tin and mercury acting as the hetero-atoms.