Rapid and exothermic solid-state synthesis of metal oxyhalides and their solid solutions via energetic metathesis reactions

Rapid solid-state metathesis reaction chemistry has been extended to the production of layered metal oxyhalide systems. This article describes the successful synthesis of crystalline BiOX (X=Cl, I), and lanthanide oxychlorides (LnOCl, Ln=La, Sm, Gd) from metal trihalides and Na₂O₂ in seconds. These known materials contain halide double layers separating M-O layers. Powder X-ray diffraction results on the metathesis metal oxyhalide products agree with prior literature reports. The morphological and compositional properties of the metal oxyhalide products are described. The rapid production of well-mixed paramagnetic Gd_xSm_1−xOCl solid-solution materials was achieved using physical mixtures of SmCl₃ and GdCl₃ precursors reacted with Na₂O₂. The room-temperature magnetic properties of these materials with varying compositions are also described. As expected, magnetism, unit cell parameters, and M-O vibrational bands are all dependent on metal composition in the solid-solution products and vary in an approximately linear Vegard's law fashion.     

Efficient synthesis of macrocyclic paracyclophanes by ring-closing metathesis dimerization and trimerization reactions

Ring-closing metathesis reactions of para-disubstituted aromatic substrates produced macrocyclic [n.n]-, and [n.n.n]paracyclophanes efficiently through dimerization and trimerization reactions. Sufficiently long alkyl chains allowed direct monocyclizations to yield [n]paracyclophanes. A small library of paracyclophanes were generated by the combinatorial cross-metathesis approach.     

Ring-closing olefin metathesis reactions; synthesis of iso-β-bisabolol

A ring-closing olefin metathesis is the key step in a synthesis of the rare iso-β-bisabolol found in sandalwood oils.     

A straightforward synthesis of 1,3-dichloro-5,8-dihydroisoquinoline by consecutive Stille cross-coupling and metathesis reactions

An efficient three-step synthetic route from 2,6-dichloro-4-iodopyridine to 1,3-dichloro-5,8-dihydroisoquinoline is described. A ring-closing-metathesis reaction constitutes the key step in this synthetic sequence. The reactivity of both chloro atoms is demonstrated in a Suzuki arylation reaction.     

Enhanced solid-state metathesis routes to carbon nanotubes

Ignition of three solids creates multiwalled carbon nanotubes in seconds. A solid-state metathesis (exchange) reaction between hexachloroethane (C2Cl6) and lithium acetylide (Li2C2) with 5% cobalt dichloride (CoCl2) added as an initiator produces up to 7% carbon nanotubes, as observed via transmission electron microscopy. Using the concept that sulfur can promote nanotube growth, the reaction yield can be increased to 15% by switching to CoS as the initiator. The more readily available, inexpensive calcium carbide (CaC2) can be substituted for lithium acetylide while maintaining comparable yields. Switching initiators to FeS can be used to further enhance the yield. A systematic study of the C2Cl6/CaC2 reaction system indicates that a yield up to 25% can be realized by using 6% FeS as the initiator. Reaction temperatures for the C(2)Cl6/CaC2 system of up to 3550 degrees C are calculated using thermodynamic data assuming quantitative yield and adiabatic conditions.     

Rapid solid-state metathesis routes to aluminum nitride

Metathesis (exchange) reactions offer the possibility of controlling temperature through a judicious choice of precursors. Here, a reaction between AlCl(3) and Ca(3)N(2) is found to produce phase-pure aluminum nitride (AlN) in seconds. The CaCl(2) byproduct salt, whose formation drives this highly exothermic reaction, is simply washed away after reaction completion. SEM images demonstrate that the AlN product is a micron-sized powder, while TEM shows well-formed crystallites. Thermodynamic calculations indicate that a reaction temperature of 2208 K could be reached under adiabatic conditions. Using an in situ thermocouple and a stainless steel reactor vessel to hold the precursors, a reaction temperature of 1673 K is measured 0.8 s after initiation. Switching to a thermally insulating ceramic vessel produces a maximum reaction temperature of 2010 K because of the more nearly adiabatic conditions. The high reaction temperature appears to be critical to forming phase-pure AlN. Experiments with Li(3)N, instead of Ca(3)N(2), produce lower temperatures (1513 K), resulting in both Al and Al(2)O(3) impurities.     

Low-temperature, solvent-free solid-state synthesis of single-crystalline titanium nitride nanorods with different aspect ratios

Titanium nitride nanorods have been successfully synthesized by low temperature solid-state metathesis of titanium (III) chloride and sodium azide without using any organic solvent. The conditions required for the synthesis of these nanorods have been optimized. It was found that the temperature and time of reaction had a significant effect on the product morphology. Thermal treatment at 360 °C, for 3 days gave the nanorods of the aspect ratio ∼10 (i.e. diameter ∼50 nm and length ∼ 500 nm), whereas the thermal treatment at 400 °C for 3 days gave the nanorods of the aspect ratio ∼50 (i.e. diameter ∼50 nm and length ∼2-3 μm). Scanning and transmission electron microscopies clearly showed the rod-type morphology. Further evidence for the phase purity and crystallinity of titanium nitride nanorods was given by X-ray diffraction, field emission high-resolution electron microscopy and X-ray photoelectron spectroscopy analyses.     

Efficient synthesis of 4-vinyl α,β-unsaturated γ-lactams by ring-closing enyne metathesis reactions

The ring-closing enyne metathesis reaction of alkyl 2-substituted-2-(N-alkynyl acrylamido)esters using the first-generation Grubbs’ catalyst afforded five-membered lactams bearing a 1,3-diene moiety in high isolated yields. In the reaction process, the presence of ethylene gas is essential.     

Topochemical solid-state reactions and problems of selective synthesis of fullerene derivatives

The characteristic features of polyaddition of small functional groups to fullerenes are considered. The review summarizes the results of experimental and theoretical studies of topochemical solid-state fluorination of fullerene C₆₀ with inorganic variable-valence transition metal fluorides and elemental fluorine in chemically active matrices. The thermodynamic and kinetic aspects of the reactions and the factors responsible for selectivity are considered.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 32–50, January, 2005.     

Amorphous and nanocrystalline luminescent Si and Ge obtained via a solid-state chemical metathesis synthesis route

A new solid-state metathesis synthesis route was applied to obtain bulk samples of amorphous or microcrystalline Si and Ge. The method involves reaction of Zintl phases such as NaSi or NaGe, with ammonium or metal (e.g., CuCl, CoBr₂) halides. The driving force for the solid-state reaction is provided by the formation of alkali halides and the transition metals or metal silicides, or gaseous ammonia and hydrogen. The semiconductors were purified by washing to remove other solid products. The amorphous semiconductors were obtained in bulk form from reactions carried out at 200-300 °C. Syntheses at higher temperatures gave rise to microcrystalline semiconductors, or to micro-/nanocrystalline particles contained within the amorphous material. Similar crystalline/amorphous composites were obtained after heat treatment of bulk amorphous materials.     

Tandem radical reactions and ring-closing metathesis. Application in the synthesis of cyclooctenes

[reaction: see text] Fumarate- and acrylate-substituted oxazolidinones undergo tandem radical reaction to form dienes in moderate to good yields. The resulting dienes provide cyclooctenes in moderate to good yields after ring-closing metathesis (RCM). The role of the carbon backbone substituents and other variables in the efficiency of the eight-membered ring formation is discussed.     

Solvents for ring-closing metathesis reactions

A study of the influence of eight diverse solvents on a Grubbs II-catalysed ring-closing metathesis (RCM) reaction reveals a complex dependence of the different reaction steps on the solvent and suggests acetic acid as a useful solvent for RCM reactions.     

Organic solid-state reactions

The role of voids and cracks in solid-state reaction between 8-hydroxyquinoline and phthalic anhydride has been investigated. 8-hydroxyquinoline reacts with phthalic anhydride both in solution and in solid state, forming a 1:1 yellow-colored complex. X-ray diffraction studies prove that the complex obtained from the solid-state reaction is the same as that obtained from solution. Several techniques have been used to study the kinetics of the reaction in the solid state. Kinetic studies by capillary technique showed that surface migration is the mode of diffusion of reactant concerned. Dilatometric technique confirms the formation of cracks and voids in the systems and shows that the reaction is propagated through the channels.     

Transformation reactions involving metathesis polymerisation

Transformation reactions provide a facile route to synthesise block copolymers that cannot be made from a single polymerisation mode. A variety of transformation reactions involving free radical, cationic, anionic, group transfer, Ziegler–Natta and metathesis are known. In this article, transformation reaction involving metathesis polymerisation is reviewed.     

Valorisation of vegetable oils by heterogeneous catalysis via metathesis reactions

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Low-temperature viscoelasticity of poly-oxymethylene by radiation-induced solid-state polymerization of trioxane single crystal

Summary The polymerizate is a porous, white cylinder of polyoxymethylene, whose direction of crystal axis is unique. The dynamic viscoelasticity was measured by the vibrating-reed-method at –180° +10 °C. The existence of the -dispersion is doubtful in this sample. Therefore we can conclude that (i) the amorphous part is negligibly small both on the surface and inside of this sample, and (ii) the vibration of molecular chains is prohibited even on the surface of a single crystal.

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Zusammenfassung Das Polymerisat ist ein poröser, weißer Zylinder von Polyoxymethylen mit einheitlich ausgerichteter Kristallachse. Die dynamische Viscoelastizität wurde zwischen –180° und +10 °C nach der Methode des vibrierenden Stäbchens bestimmt. Die Existenz des-Dispersionsgebiets ist bei dieser Probe zweifelhaft. Wir können daher folgern, daß 1. der amorphe Anteil vernachlässigbar klein — sowohl an der Oberfläche wie im Innern — ist und daß 2. die Schwingung der Molekülketten sogar auch in der Grenzfläche eines Einkristalls behindert, unterbunden ist.

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This work was presented at the 43rd Annual Meeting of Virginia Academy of Science, Richmond, Virginia, May 7, 1965.     

Physico-geometric kinetics of solid-state reactions by thermal analyses

The physico-geometric kinetics for the solid-state reactions by thermoanalytical (TA) measurements were reexamined by focusing some fundamental aspects: (1) the fundamental kinetic equation, (2) the kinetic model function, (3) the fractional reaction , and (4) the apparent kinetic parameters. It was pointed out that some pitfalls in the practical kinetic study are originated by the disagreement between the kinetic information from the TA measurements and the theory of the physico-geometric kinetics. In order to increase the degree of coordination between the theory and practice, several attempts were made from both the theoretical and experimental points of views. The significance of the apparent kinetic parameters was discussed with a possible orientation for obtaining the reliable kinetic parameters.I would like to thank to Profs H. Tanaka, J. esták, J. M. Criado, A. K. Galwey and Dr. J. Malek for their kind supports.     

Synthesis of new bicyclic lactam peptidomimetics by ring-closing metathesis reactions

An efficient and versatile synthetic method for the preparation of new fused bicyclic lactams 3a and 3b is described. The spirane cyclopentane nucleus was easily installed by diallylation of the pyroglutamate derivative 18 followed by ring-closing metathesis (RCM). A more practical and stereoselective method for the allylation of the α-methoxy carbamate 21, involving the use of InCl₃ as a Lewis acid, was developed. In the crucial coupling reaction of the diastereomeric mixture of cis- and trans-pirrolidine derivatives 5a and 5b with N-Cbz vinyl phenylalanine only the cis isomer was found to react. An RCM reaction on the dipeptides 25a and 25b followed by catalytic hydrogenation, gave the final epimeric bicyclic lactams 3a and 3b. The same synthetic sequence on the model compound 7, lacking the spiro cyclopentane nucleus, is also reported.