Search results for "polymer chemistry"

ChemInform Abstract: A New Versatile Synthesis of N,N′,N′′,N′′′-Tetra(2-carboxyethyl)- and N,N′,N′′,N′′′-Tetra(3-aminopropyl)-tetraazacycloalkanes by…

2010

Abstract A smooth and convenient one step synthesis of N,N′,N″,N″′-tetra-(2-carboxyethyl)-tetraazacycloalkanes is reported. These compounds are synthesized by Michael addition of tetraazacycloalkanes to acrylic acid. The same Michael addition of tetraazacycloalkanes to an excess of acrylonitrile also leads to the corresponding tetracyanoethylated derivatives. The reduction of such tetracyanoethylated compounds is a new way of preparation for the corresponding primary amines.

1992

Donor-Stabilized Phosphenium Adducts as New Efficient and Immobilizing Ligands in Palladium-Catalyzed Alkynylation and Platinum-Catalyzed Hydrogenati…

2009

The straightforward synthesis of a new donor-stabilized phosphenium ligand 3d by addition of bromodifurylphosphine to 1,3-dimethylimidazolium-2-carboxylate 1 is described. The obtained ligand exhibits a very strong π-acceptor character, comparable to that of triphenyl phosphite [P(OPh) 3 ] or of tris-halogenophosphines, with a v CO (A 1 ) at 2087 cm ―1 for its nickel tricarbonyl complex. This ligand, as well as the related 3a which was obtained from chlorodiphenylphosphine, were tested in palladium-catalyzed aryl alkynylation and in the platinum-catalyzed selective hydrogenation of chloronitrobenzenes, both in an ionic liquid phase. In C―C bond cross-coupling we observed that the increase o…

Electrochemical and bioelectrocatalytical properties of novel block-copolymers containing interacting ferrocenyl units

2008

The electrochemical characterization of three different polystyrene-b-polybutadiene block-copolymers, functionalized with diferrocenylsilane units, is reported. The PB-blocks have been functionalized with different fractions of electronicall y communicated, PSm-PB„ p (HSiMeFc2)p units, where m = 615, n = 53, p = 39 (1), m = 375, n = 92, p = 76 (2) and m = 455, n = 204, p = 170 (3). Electrochemical character­ ization has been carried out both in solution and after electrochemical deposition onto platinum electrodes. The bioelectrocatalytical properties of electrodes modified with the polymers in the nicotinamide dinucleotide (NADH) and glucose oxidase (GOx) oxidations have been investigated …

A sigma-donor with a planar six-pi-electron B2N2C2 framework: anionic N-heterocyclic carbene or heterocyclic terphenyl anion?

2006

Nickel as a Lewis Base in a T‐Shaped Nickel(0) Germylene Complex Incorporating a Flexible Bis(NHC) Ligand

2018

Flexible, chelating bis(NHC) ligand 2, able to accommodate both cis- and trans-coordination modes, was used to synthesize (2)Ni(η 2 -cod), 3. In reaction with GeCl2, this produced (2)NiGeCl2, 4, featuring a T-shaped Ni(0) and a pyramidal Ge center. Complex 4 could also be prepared from [(2)GeCl]Cl, 5, and Ni(cod)2, in a reaction that formally involved Ni-Ge transmetalation, followed by coordination of the extruded GeCl2 moiety to Ni. A computational analysis showed that 4 possesses considerable multiconfigurational character and the Ni→Ge bond is formed through σ-donation from the Ni 4s, 4p, and 3d orbitals to Ge. (NHC)2Ni(cod) complexes 9 and 10, as well as (NHC)2GeCl2 derivative 11, incor…

Electrochemistry and spectroelectrochemistry of heterobimetallic porphyrin-corrole dyads. Influence of the spacer, metal ion, and oxidation state on …

2005

Combined electrochemical and UV-visible spectroelectrochemical methods were utilized to elucidate the prevailing mechanisms for electroreduction of previously synthesized porphyrin-corrole dyads of the form (PCY)H2Co and (PCY)MClCoCl where M = Fe(III) or Mn(III), PC = porphyrin-corrole, and Y is a bridging group, either biphenylenyl (B), 9,9-dimethylxanthenyl (X), anthracenyl (A), or dibenzofuranyl (O). These studies were carried out in pyridine, conditions under which the cobalt(IV) corrole in (PCY)MClCoCl is immediately reduced to its Co(III) form, thus enabling direct comparisons with the free-base porphyrin dyad, (PCY)H2Co(III) under the same solution conditions. The compounds are all r…

1977

Copolymers from styrene and 1-vinylimidazoles (4a–f), form low spin adducts with iron(II) porphyrins and iron(III) porphyrins, when the content of imidazolyl groups in the polymer is ten mole percent or more. With polymers having a content of imidazolyl groups of less then one mole percent, only high spin adducts are observed. With terpolymers, in which the porphyrin is covalently bound to the copolymer the same phenomenon is observed. Only the high spin Fe(II) porphyrin adducts in the solid state adsorb molecular oxygen like cobalt(II) porphyrins under the same conditions. Adsorptions and desorptions of oxygen are much slower in the cases of iron(II) porphyrins than with the cobalt(II) por…

Influence of Acidic Support in Metallocene Catalysts for Ethylene Polymerization

2001

Abstract We studied a ZSM-5 zeolite as metallocene support for ethylene polymerization. We transformed the Na-ZSM-5 into H-ZSM-5. After the cation exchange, the zeolite was calcined at three different temperatures. Characterization of the material indicated that by means of the calcination procedure it is possible to produce dealuminization with an increase in extraframework aluminum (EFAL). We prepared zirconocene-supported catalysts on zeolitic supports using two preparation methods. The higher activity was observed with the zirconocene supported on ZSM-5 pretreated at 900°C. We think that the dealuminization process generates an increase in EFAL. This EFAL is responsible for the higher a…

Imidotungsten(VI) complexes with chelating phenols as ROMP catalysts

2011

Abstract Tungsten(VI) complexes of the type [W(NPh)Cl3(L)] (L = chelating phenolate) were studied as catalyst precursors for ROMP of 2-norbornene, dicyclopentadiene and 5-vinyl-2-norbornene. These compounds form active catalysts when treated by ethyl magnesium bromide. Moreover, polymerisations can be run under ambient atmosphere without complicated inert atmosphere techniques. Synthesis and crystal structure of a new precursor complex [W(NPh)Cl3(LS)] (LS = 2,4-di-tert-butyl-6-(phenylthiomethyl)phenolate) are also described.