Search results for "element"

Base-assisted synthesis of 4-pyridinate gold(I) metallaligands: a study of their use in self-assembly reactions

2021

Made available in DSpace on 2021-06-25T12:16:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-06 Ministerio de Economia y Competitividad (MINECO/FEDER) of Spain Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The synthesis of di- and tritopic gold(I) metallaligands of the type [(Au4-py)(2)(mu(2)-diphosphane)] (diphosphane = bis(diphenylphosphanyl)isopropane or dppip (1), 1,2-bis(diphenylphosphanyl)ethane or dppe (2), 1,3-bis(diphenylphosphanyl)propane or dppp (3) and 1,4-bis(diphenylphosphanyl)butane or dppb (4)) and [(Au4-py)(3)(mu(3)-triphosphane)] (triphosphane = 1,1,1-tris(diphenylphosph…

Homoleptic Pnictogen-Chalcogen Coordination Complexes

2012

The synthesis and structural characterization of dicationic selenium and tellurium analogues of the carbodiphosphorane and triphosphenium families of compounds are reported. These complexes, [Ch(dppe)][OTf](2) [Ch = Se, Te; dppe = 1,2-bis(diphenylphosphino)ethane; OTf = trifluoromethanesulfonate], are formed using [Ch](2+) reagents via a ligand-exchange protocol and represent extremely rare examples of homoleptic pnictogen → chalcogen coordination complexes. The corresponding arsenic compounds were also prepared, [Ch(dpAse)][OTf](2) [Ch = Se, Te; dpAse = 1,2-bis(diphenylarsino)ethane], exhibiting the first instance of an arsenic → chalcogen dative bond. The electronic structures of these un…

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…

Thermal and Photoinduced Electron Transfer in Directional Bis(terpyridine)ruthenium(II)–(Bipyridine)platinum(II) Complexes

2013

Metalloligands L1 and L2 consisting of directional bis(terpyridine)ruthenium(II) units and bipyridine moieties were constructed by amide formation. From these metalloligands two Ru–Pt heterobimetallic complexes 1 and 2 were derived by a building-block method by means of platination with [PtCl2(dmso)2]. Both bimetallic complexes 1 and 2 feature metal-to-ligand charge transfer (MLCT) absorptions, and emission occurs at room temperature in fluid solution from 3MLCT(Ru) states in all cases. Energy transfer from platinum to ruthenium is observed in 2 but not in 1 (light harvesting). The one-electron-reduced species [1]– and [2]– were prepared by reduction of 1 and 2 with decamethylcobaltocene. E…

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…

Experimental study of the long range interactions between a Na (3S) and a Rb (5S) atom

2005

Transitions to near asymptotic levels of the a3Σ+ and the X1Σ+ electronic states in NaRb were recorded by high resolution Fourier transform spectroscopy technique. The hyperfine splitting of the a3Σ+ state levels was analysed. The application of coupled channels calculations is discussed for determination of accurate potential energy curves of the a3Σ+ and the X1Σ+ states capable for reliable description of cold collisions between a Na and a Rb atoms in their ground states.

Green-Light Activation of Push-Pull Ruthenium(II) Complexes.

2020

Abstract Synthesis, characterization, electrochemistry, and photophysics of homo‐ and heteroleptic ruthenium(II) complexes [Ru(cpmp)2]2+ (22+) and [Ru(cpmp)(ddpd)]2+ (32+) bearing the tridentate ligands 6,2’’‐carboxypyridyl‐2,2’‐methylamine‐pyridyl‐pyridine (cpmp) and N,N’‐dimethyl‐N,N’‐dipyridin‐2‐ylpyridine‐2,6‐diamine (ddpd) are reported. The complexes possess one (32+) or two (22+) electron‐deficient dipyridyl ketone fragments as electron‐accepting sites enabling intraligand charge transfer (ILCT), ligand‐to‐ligand charge transfer (LL'CT) and low‐energy metal‐to‐ligand charge transfer (MLCT) absorptions. The latter peak around 544 nm (green light). Complex 22+ shows 3MLCT phosphorescenc…

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.

A Versatile Palladium/Triphosphane System for Direct Arylation of Heteroarenes with Chloroarenes at Low Catalyst Loading

2010

International audience; Put a ring on it: The use of an air-stable, robust palladium/tridentate phosphane catalyst in direct C[BOND]H and C[BOND]Cl activation reactions is reported (see scheme; DMAc=N,N-dimethylacetamide, TBAB=tetra-n-butylammonium bromide). Electron-rich, electron-poor, and polysubstituted furans (X=O), thiophenes (X=S), pyrroles (X=NR5), and thiazoles were arylated with chloroarenes in the presence of the catalyst.

Synthesis of novel fluorinated building blocks via halofluorination and related reactions.

2020

A study exploring halofluorination and fluoroselenation of some cyclic olefins, such as diesters, imides, and lactams with varied functionalization patterns and different structural architectures is described. The synthetic methodologies were based on electrophilic activation through halonium ions of the ring olefin bonds, followed by nucleophilic fluorination with Deoxo-Fluor®. The fluorine-containing products thus obtained were subjected to elimination reactions, yielding various fluorine-containing small-molecular entities.