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N Ligands (n + ligand)

Distribution by Scientific Domains

Chemistry	73%
Polymers and Materials Science	26%

Selected Abstracts

A P,N Ligand with Central and Axial Chiral Elements: Synthesis and Application in Allylic Alkylation.

CHEMINFORM, Issue 50 2006
Igor Mikhael
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Gold(I) Complexes of P,N Ligands and Their Catalytic Activity

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2010
Chosu Khin
Abstract Gold(I) complexes were readily prepared by reaction of the respective ligands with (Me2S)AuCl in CH2Cl2. Complexes of formula LAuCl {L = diphenyl(2-pyridyl)phosphane (PPh2Py), (R)-(+)-4-[(2)-(diphenylphosphanyl)-1-naphthyl]- N -[(R)-1-phenylethyl]-1-phthalazinamine (PINAP)} were obtained when a 1:1 molar ratio of ligand to starting gold precursor was used. When a 2:1 ratio of ligand to gold precursor was used with PPh2Py or MandyPhos as ligands, complexes of the type L2AuCl were obtained. All complexes were fully characterized, and single-crystal X-ray structures could be determined for four complexes. Chloride ions were removed by reaction with silver salts, such as AgNTf2, AgOTf and AgBF4, for the use of these complexes as catalysts. After the catalytic reaction with alkynes and alcohols in acetonitrile, a unique trinuclear gold(I) complex derived from [(PPh2Py)Au]BF4 could be characterized by X-ray structural analysis, showing a mode of catalyst deactivation. [source]

Highly Enantioselective Iridium-Catalyzed Hydrogenation of Trisubstituted Olefins, ,,,-Unsaturated Ketones and Imines with Chiral Benzylic Substituted P,N Ligands

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010
Wei-Jing Lu
Abstract The benzylic substituted P,N ligands, diphosphinobenzyloxazolines, showed their high catalytic activity as well as asymmetric induction in the iridium-catalyzed asymmetric hydrogenation of unfunctionalized alkenes, ,,,-unsaturated esters, allyl alcohols, ,,,-unsaturated ketones, and imines, providing the corresponding chiral products in high ee with high conversion. [source]

Pyranoside Phosphite-Oxazoline Ligand Library: Highly Efficient Modular P,N Ligands for Palladium-Catalyzed Allylic Substitution Reactions.

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009
A Study of the Key Palladium Allyl Intermediates
Abstract We have screened a library of modular phosphite-oxazoline ligands for asymmetric allylic substitution reactions. The library is efficiently prepared from the commercially available and cheap D -glucosamine. The introduction of a phosphite moiety into the ligand design is highly advantageous for the product outcome. Therefore, this ligand library affords good-to-excellent reaction rates [TOFs up to 600 mol substrate×(mol Pd×h),1] and enantioselectivities (ees up to 99%) and, at the same time, shows a broad scope for mono-, di- and trisubstituted linear hindered and unhindered substrates and cyclic substrates. The NMR studies on the palladium allyl intermediates provide a deeper understanding about the effect of the ligand parameters on the origin of enantioselectivity. [source]

ChemInform Abstract: Synthesis of Sulfoximine-Derived P,N Ligands and Their Applications in Asymmetric Quinoline Hydrogenations.

CHEMINFORM, Issue 36 2008
Sheng-Mei Lu
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Application of a New Family of P,N Ligands to the Highly Enantioselective Hydrosilylation of Aryl Alkyl and Dialkyl Ketones.

CHEMINFORM, Issue 5 2003
Beata Tao
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

ChemInform Abstract: Enantioselective Copper-Catalyzed Conjugate Addition of Diethylzinc to Enones Using New Chiral P,N Ligands Composed of (S)-2-Alkyl-2-aminoethylphosphines and ,-Substituted Pyridines.

CHEMINFORM, Issue 11 2001
Toshiaki Morimoto
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Amino-phosphanes in RhI -Catalyzed Hydroformylation: New Mechanistic Insights Using D2O as Deuterium-Labeling Agent

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2006
Jacques Andrieu
Abstract In previous work, we have demonstrated that the dangling amino group in amino-phosphane ligands increases the rate of Rh-catalyzed styrene hydroformylation as a function of the amino group basicity and of the distance between the P and N functions. We now report additional stereochemical and mechanistic insights resulting from new catalytic experiments performed with Rh-,-P,N catalytic systems in the presence of D2O. In addition to the expected D0 product, the formation of the ,-D1 aldehyde, PhCH(CH2D)CHO was observed in all cases by 1H and 13C NMR spectroscopy, indicating that H/D exchange occurs for the rhodium-hydride complex. Minor amounts of a ,-D2 product, PhCH(CHD2)CHO, were also formed under certain conditions, demonstrating the reversibility of the olefin coordination step. The composition of the aldehyde mixture is slightly affected by the nature of the catalytic precursor or the P,N ligand used. In the specific case of the ,-P,N ligand [,-P,N = (SAr,SC)-Ph2PCH{o -C6H4Cl(Cr(CO)3)}NHPh], in combination with the [RhCl(COD)]2 precatalyst, products PhCD(CH3)CHO (,-D1) and PhCD(CH2D)CHO (,,,-D2) were also produced. This result suggests a reversible deprotonation assisted by an intramolecular H-bonding interaction between the dangling ammonium function and the carbonyl moiety. This isotopic exchange process decreases the asymmetric induction from 14 to 7,% ee when using the enantiopure version of this ligand. Aldehydes bearing a D atom on the formyl group, e.g. PhCH(CH3)CDO, were never observed. The latter observation excludes protonolysis of the rhodium-acyl intermediate as the aldehyde forming step. In addition, it also excludes a bimolecular reaction involving the rhodium-acyl and rhodium-hydride intermediates.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Ionic Iridium(III) Complexes with Bulky Side Groups for Use in Light Emitting Cells: Reduction of Concentration Quenching

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
Carsten Rothe
Abstract Here, the photophysics and performance of single-layer light emitting cells (LECs) based on a series of ionic cyclometalated Ir(III) complexes of formulae and where ppy, bpy, and phen are 2-phenylpyridine, substituted bipyridine and substituted phenanthroline ligands, respectively, are reported. Substitution at the N,N ligand has little effect on the emitting metal-ligand to ligand charge-transfer (MLLCT) states and functionalization at this site of the complex leads to only modest changes in emission color. For the more bulky complexes the increase in intermolecular separation leads to reduced exciton migration, which in turn, by suppressing concentration quenching, significantly increases the lifetime of the excited state. On the other hand, the larger intermolecular separation induced by bulky ligands reduces the charge carrier mobility of the materials, which means that higher bias fields are needed to drive the diodes. A brightness of ca. 1000,cd,m,2 at 3,V is obtained for complex 5, which demonstrates a beneficial effect of bulky substituents. [source]

Multifunctional Crosslinkable Iridium Complexes as Hole Transporting/Electron Blocking and Emitting Materials for Solution-Processed Multilayer Organic Light-Emitting Diodes

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Biwu Ma
Abstract Here, a new series of crosslinkable heteroleptic iridium (III) complexes for use in solution processed phosphorescent organic light emitting diodes (OLEDs) is reported. These iridium compounds have the general formula of (PPZ-VB)2Ir(C,N), where PPZ-VB is phenylpyrazole (PPZ) vinyl benzyl (VB) ether; and the C,N ligands represent a family of four different cyclometallating ligands including 1-phenylpyrazolyl (PPZ) (1), 2-(4,6-difluorophenyl)pyridyl (DFPPY) (2), 2-(p-tolyl)pyridyl (TPY) (3), and 2-phenylquinolyl (PQ) (4). With the incorporation of two crosslinkable VB ether groups, these compounds can be fully crosslinked after heating at 180,°C for 30,min. The crosslinked films exhibit excellent solvent resistance and film smoothness which enables fabrication of high-performance multilayer OLEDs by sequential solution processing of multiple layers. Furthermore, the photophysical properties of these compounds can be easily controlled by simply changing the cyclometallating C,N ligand in order to tune the triplet energy within the range of 3.0,2.2,eV. This diversity makes these materials not only suitable for use in hole transporting and electron blocking but also as emissive layers of several colors. Therefore, these compounds are applied as effective materials for all-solution processed OLEDs with (PPZ-VB)2IrPPZ (1) acting as hole transporting and electron blocking layer and host material, as well as three other compounds, (PPZ-VB)2IrDFPPY (2), (PPZ-VB)2IrTPY(3), and (PPZ-VB)2IrPQ(4), used as crosslinkable phosphorescent emitters. [source]

Evolution of iron catalysts for effective living radical polymerization: P,N chelate ligand for enhancement of catalytic performances

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2008
Chihiro Uchiike
Abstract Iron catalysts were evolved for more active transition metal-catalyzed living radical polymerization through design of the ligands. In situ introduction of P,N chelate-ligands, consisting of hetero-coordinating atoms [phosphine (P) and nitrogene (N)], onto FeBr2 effectively catalyzed living radical polymerization of methyl methacrylate (MMA) in conjunction with a bromide initiator, where the monomer-conversion reached over 90% without dropping the rates and the molecular weights of obtained PMMAs were well controlled. The benign effects of the "hetero-chelation" were demonstrated by comparative experiments with homo-chelate ligands (P,P, N,N), model compounds of the composed coordination site, and the combinations. We successfully achieved an isolation of iron complex with a P,N ligand [FeBr2(DMDPE); DMDPE: (R)- N,N -dimethyl-1-(2-(diphenylphosphino)phenyl)-ethanamine], which was superior to the conventional catalyst [FeBr2(Pn -Bu)2] with respect to controllability and activity, especially at the latter stage. The catalyst was almost quantitatively removed by water washing after polymerization. It was also effective for living polymerization of styrene. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6819,6827, 2008 [source]

Insights into CO/Styrene Copolymerization by Using PdII Catalysts Containing Modular Pyridine,Imidazoline Ligands

CHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004
Amaia Bastero Dr.
Abstract Continuing our studies into the effect that NN, ligands have on CO/styrene copolymerization, we prepared new C1 -symmetrical pyridine,imidazoline ligands with 4,,5,- cis stereochemistry in the imidazoline ring (5) and 4,,5,- trans stereochemistry (6,10) and compared them with our previously reported ligands (1,4). Their coordination to neutral methylpalladium(II) (5,a,10,a) and cationic complexes (5,b,10,b), investigated in solution by NMR spectroscopy, indicates that both the electronic and steric properties of the imidazolines determine the stereochemistry of the palladium complexes. The crystal structures of two neutral palladium precursors [Pd(Me)2,nCln(NN,)] (n=1 for 8,a; n=2 for 9,a,) show that the PdN coordination distances and the geometrical distortions in the imidazoline ring depend on the electronic nature of the substituents in the imidazoline fragment. Density functional calculations performed on selected neutral and cationic palladium complexes compare well with NMR and X-ray data. The calculations also account for the formation of only one or two stereoisomers of the cationic complexes. The performance of the cationic complexes as catalyst precursors in CO/4- tert -butylstyrene copolymerization under mild pressures and temperatures was analyzed in terms of the productivity and degree of stereoregularity of the polyketones obtained. Insertion of CO into the PdMe bond, which was monitored by multinuclear NMR spectroscopy, shows that the N ligand influences the stereochemistry of the acyl species formed. [source]

Multifunctional Crosslinkable Iridium Complexes as Hole Transporting/Electron Blocking and Emitting Materials for Solution-Processed Multilayer Organic Light-Emitting Diodes

Highly Enantioselective Iridium-Catalyzed Hydrogenation of Trisubstituted Olefins, ,,,-Unsaturated Ketones and Imines with Chiral Benzylic Substituted P,N Ligands

The Development of Enantioselective Rhodium-Catalysed Hydroboration of Olefins

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2005
Anne-Marie Carroll
Abstract Rhodium-catalysed enantioselective hydroboration of olefins is a valuable synthetic transformation, typically employing a chiral catalyst and an achiral borane source. The pertinent chemo-, regio- and enantioselectivity issues of this reaction are discussed. However, the main emphasis of this review is on the evolution of catalytic asymmetric hydroboration. This has primarily relied upon the development and application of chiral bidentate P,P and P,N ligands which have exhibited varying degrees of success in this transformation. [source]