A new organometallic compound of titanium: indenylcyclooctatetraenyltitanium(III)

The synthesis of a new organotitanium compound, C₉H₇TiC₈H₈, is described. The compound is green, thermally stable, but very sensitive to water and oxygen. The infrared spectrum indicates that the C₉H₇^? and C₈H₈^2? groups are π-bonded to the metal. During the preparation, titanium(IV) is reduced to titanium(III).     

Supramolecular assemblies based on organometallic quinonoid linkers: a new class of coordination networks

Self-assembly of coordination frameworks exhibiting original architectures is an active area of research. Generally, such assemblies are constructed from organic spacers and transition metals of different geometrical structures. Herein, we report a novel class of supramolecular coordination assemblies with organometallic linkers based on metalated quinonoid and thioquinonoid complexes that serve as spacers. The organometallic ligands are stable and have the general formula [Cp*M(eta(4)-benzoquinone)] (o- and p-benzoquinone, Cp*=C(5)Me(5), M=Rh, Ir) and [Cp*Ir(eta(4)-thiobenzoquinone)] (o- and p-thiobenzoquinone). These units bind through both oxygen or sulfur atoms to metal ions of different coordination geometry, such as Cu(I), Ag(I), and Pt(II), to generate supramolecular coordination networks, with the metalated quinonoid or thioquinonoid linkers acting as backbones and the metal centers as nodes. This novel family of supramolecular assemblies exhibits short pi-pi and MM interactions. These results illustrate successfully the role of the organometallic linkers to produce an impressive range of novel supramolecular architectures that hold promise for the development of functional materials.     

Biphenyls, a new class of compound that inhibits platelet-activating factors

Honokiol (1), a constituent of Magnoliae cortex, and related synthetic biphenyls inhibited the platelet aggregation induced by a few aggregating agents. In particular, compounds 3, 5, and 10 had an inhibitory effect on platelet activating factor (PAF), which provides a new class of PAF inhibitor.     

The first NH aldimine organometallic compound. Isolation and crystal structure

The first NH aldimine organometallic derivative is unexpectedly formed by the cleavage of the nitrogen-carbon bond of the amino acid fragment of the Schiff base 2,4,6-Me3C6H2CH=NCH(CH2Ph)COOEt when the imine is treated with palladium acetate.     

A new class of epoxy thermosets

The reinforcing strategies of epoxy thermosets rely on the control of the phase separation between the additive and the growing thermoset. With standard additives, such as reactive liquid rubbers, the length scale of the resulting domains is the micrometer. Here, we present a route that enable a control of the morphology down to the nanometer scale. This strategy is based upon the self-assembly process of blends of epoxy and SBM triblock copolymers, namely Poly(Styrene-b-1,4 Butadiene-b-Methyl methacrylate). It relies on the respective affinities between the epoxy precursors and each of the three blocks. Liquid epoxy has a strong affinity for PMMA, whilst it is not miscible with polystyrene nor polybutadiene at standard processing temperatures. Thus, within the reactive system, microphase separation leads to a regular network of S-B domains. This nanostructure is governed by thermodynamics. The size and geometry of the dispersed domains are controlled by the concentration and the ratio between blocks lengths. The domain size is of the order of magnitude of the chain length, ranging typically from 10 to 30 nanometers. What controls the blend's morphology throughout the curing process of the thermoset was one topic on which we focused our interest. Nanostructured thermosets have been obtained. These supramolecular architectures yield significant toughness improvements while preserving the transparency of the material. The reinforcing mechanisms are not yet fully understood : it is intriguing to induce significant toughening with elastomer domains smaller than 30 nanometers in diameter. Besides being efficient epoxy tougheners, SBM can broaden the scope of applications of thermosets due to specific rheological behaviors. Thanks to the self assembly process taking place in the blend of the SBM block copolymers with the epoxy thermosets precursors, the reactive solvent can be turned into a reactive gel or solid (before curing). This physical gelation is induced by the microphase separation and is thus thermoreversible. At relatively moderate loadings of block copolymers the reactive blend behaves like a thermoplastic material, with adjustable modulus and tackiness. These results evidence that SBM block copolymers open a broad area for designing new class of thermoset materials.     

A new class of spermidine-derived alkaloids

[structure: see text] Four new alkaloids, dovyalicins A-D, were isolated from Dovyalis macrocalyx. Their structures were established by two-dimensional COSY, NOESY, HSQC, and HMBC NMR experiments as well as chiroptical methods. The compounds, possessing spermidine as part of a perhydro-1,5-diazocine or a perhydro-1,4-diazepine moiety, constitute a new group of polyamine-derived alkaloids.     

Synthesis of gold nanoparticles from an organometallic compound in supercritical carbon dioxide

This article presents the synthesis of gold nanoparticles in a single-phase supercritical fluid carbon dioxide solvent. The gold nanoparticles were formed by the reduction of triphenylphosphine gold(I) perfluorooctanoate with dimethylamineborane. Transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis spectroscopy reveal the formation of gold nanoparticles of 1 nm in diameter. A high dispersion stability of the gold nanoparticles in supercritical carbon dioxide can be obtained by binding both triphenylphosphine and fluorocarbon ligands on the surface of the gold nanoparticles.     

3-Lithiomethyl-4-phenylsydnone: A new type of organometallic derivatives of sydnones

An α-lithium derivative of 3-alkyl-substituted sydnone was first synthesized by direct metallation of 3-methyl-4-phenylsydnone withn-butyllithium. The reactivity of the compound obtained was studied. Reactions of 3-lithiomethyl-4-phenylsydnone with various electrophiles can serve as a convenient method for preparation of functionalized sydnones.     

Reversible radical complex formation of an organometallic diplatinum(IV) compound

Crystallographically characterized anti-[(μ-bmptz){fac-PtBrMe₃}₂], bmptz = 3,6-bis(2-(4-methylpyridyl))-1,2,4,5-tetrazine, could be reversibly reduced at −0.36 V vs. [FeCp₂]^+/° in CH₂Cl₂/0.1 M Bu₄NPF₆ to a persistent anion. Despite the presence of two conjugatively coupled platinum(IV) centers and the bromide ligands as potential leaving groups it is the bridging bmptz ligand which accepts the added electron within the tetrazine ring as evident from EPR and UV-Vis spectroelectrochemistry of that diplatinum(IV) radical complex. The function of the methyl groups in the [fac-PtMe₃]⁺ ions is discussed in contrast with the related entity [fac-Re(CO)₃]⁺.     

A new alligator-clip compound for molecular electronics

We used the B3LYP flavor of density functional calculations to study new alligator-clip compounds for molecular electronics with platinum electrodes. First, with commonly used S-based linkage molecule 3-methyl-1,2-dithiolane (MDTL) we find that after chemisorption on Pt(1 1 1) the most stable structure is ring-opened with a binding energy of 32.44 kcal/mol. Among several alternative alligator-clip compounds we find that P-based molecules lead to much higher binding energies. For the ring-closed structure of 3-methyl-1,2-diphospholane (MDPL) a binding energy of 47.72 kcal/mol was calculated and even 54.88 kcal/mol for the ring-opened molecule. Thus, MDPL provides a more stable link to the metal surface and might increase the conductance.     

EuFCl—A new mixed-halide rare-earth compound

This paper reports the synthesis and bulk magnetic properties of a new rare-earth compound, EuFCl, isostructural with tetragonal PbFCl, and solid solutions of it with several LnOCl compounds, where Ln = Eu, Sm, Nd, Gd.     

A new approach to estimating compound density

The expediency of the polynomial approximation of physico-chemical parameters of C,H,N,O-containing compounds is shown using density as an example.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 685–687, April, 1993.     

A list of organometallic kryptoracemates

The vast majority of racemic solutions of chiral compounds apparently crystallize at room temperature in non‐Sohncke space groups as racemic crystals. However, kryptoracemic crystals composed of nearly enantiomeric pairs occasionally crystallize at room temperature, or appear as low‐temperature phases, in Sohncke space groups. As a complement to the previously published catalog of organic kryptoracemates [Fábián & Brock (2010). Acta Cryst. B 66 , 94–103], 1412 chiral organometallic crystal structures have now been extracted from the Cambridge Structural Database and analyzed. 26 are listed herein as credible kryptoracemates. The possible influence of temperature is discussed, together with some problems in characterizing and classifying these structures.     

A new class of low-molecular-weight amphiphilic gelators

A new powerful class of low-molecular-weight amphiphilic compounds has been synthesized and their structure-property relationships with respect to their gelation ability of organic solvents have been investigated. These compounds are able to gel organic solvents over a broad range of polarity. Especially polar solvents such as valeronitrile and gamma-butyrolactone can be gelled even at concentrations far below 1 wt %. It was found that the gelation ability of these asymmetrically substituted p-phenylendiamines depends on a well-balanced relation of the terminal head group, the units involved in hydrogen bonding (amide or urea groups), and on the length of the alkyl chain. With this class of new gelators it is possible to tailor thermal and mechanical properties in different organic solvents and open various application possibilities.     

A new tetradentate nitrogen ligand for organometallic catalysis: electrochemical nickel-catalyzed intramolecular cyclization

The new tetraaza-molecule, 1 has been synthesized and used as a ligand for a cationic mononuclear nickel(II) complex. This complex is an efficient catalysts for the intramolecular electrochemical cyclization of o-haloaryl compounds containing unsaturated side chains.     

A new and highly effective organometallic approach to 1,2-dehalogenations and related reactions

We investigated the reductive elimination of several functionalized and non-functionalized vic-dibromides with 1,2-diphenyl-, 1,1,2,2-tetraphenyl- and 1-phenyl-2-(2-pyridyl)-1,2-disodioethane. The reaction, involving some of the less expensive organic and inorganic reagents, proceeds under mild conditions, and is tolerant of a variety of functional groups. Extension of this procedure to similar 1,2-disubstituted compounds was also investigated. Reductive eliminations run on stereochemical probe compounds strongly suggest that this reaction proceeds via a “single electron” reductive elimination reaction pathway.