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Ligand Backbone (ligand + backbone)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Reactions of the Aluminum(I) Monomer LAl [L = HC{(CMe)(NAr)}2; Ar = 2,6- iPr2C6H3] with Imidazol-2-ylidene and Diphenyldiazomethane.

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2004
A Hydrogen Transfer from the L Ligand to the Central Aluminum Atom, Formation of the Diiminylaluminum Compound LAl(N=CPh2)
Abstract The solid-state reaction of LAl and imidazol-2-ylidene at elevated temperature (120 °C) yielded the aluminum monohydride N -heterocyclic carbene adduct [{HC[C(CH2)NAr] (CMeNAr)}AlH-{CN(R)C2Me2N(R)}] [R = iPr (1), Me (2)]. Compounds 1 and 2 have been characterized by spectroscopic (IR, and 1H and 13C NMR), mass spectrometric, and elemental analyses, and 1 was further characterized by X-ray structural analysis. These experimental data indicate that the Al,H bond is formed by hydrogen migration from one of the methyl groups of the ,-diketiminato ligand backbone. The reaction of LAl with two equivalents of diphenyldiazomethane afforded the diiminylaluminum compound LAl(N=CPh2)2 (3), while an excess of diphenyldiazomethane resulted in the formation of Ph2C=N,N=CPh2. This suggests that Ph2C=N,N=CPh2 is initially generated and then reacts further by oxidative addition to yield 3. The X-ray structural analysis reveals that compound 3 contains the shortest Al,Niminyl bond among those with a four-coordinate aluminum center. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

(3,8,9,14-Tetraethyl-2,4,13,15-tetramethyltripyrrinato)(trifluoroacetato)palladium(II)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2007
Serguei Prikhodovski
In the crystal structure, the title compound {systematic name: [2,5-bis(4-ethyl-3,5-dimethyl-2H -pyrrol-2-ylidenemethyl)-1H -pyrrolato](trifluoroacetato)palladium(II)}, [Pd(C2F3O2)(C27H34N3)], forms chiral molecules with a helical distortion of the tripyrrinate ligand backbone and an essentially planar PdN3O core, with Pd,N distances ranging from 1.977,(3) to 2.045,(3),Å and a Pd,O distance of 2.051,(2),Å. This distortion of the organic ligand is considered as the conformational answer to the steric interaction of the terminal methyl groups of the tripyrrinate ligand with the donor O atom of the trifluoroacetate group. [source]

Oxidative addition of different electrophiles with rhodium(I) carbonyl complexes of unsymmetrical phosphine,phosphine monoselenide ligands

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2006
Pratap Chutia
Abstract Dimeric chlorobridge complex [Rh(CO)2Cl]2 reacts with two equivalents of a series of unsymmetrical phosphine,phosphine monoselenide ligands, Ph2P(CH2)nP(Se)Ph2 {n = 1(a), 2(b), 3(c), 4(d)}to form chelate complex [Rh(CO)Cl(P,Se)] (1a) {P,Se = ,2 -(P,Se) coordinated} and non-chelate complexes [Rh(CO)2Cl(P,Se)] (1b,d) {P,Se = ,1 -(P) coordinated}. The complexes 1 undergo oxidative addition reactions with different electrophiles such as CH3I, C2H5I, C6H5CH2Cl and I2 to produce Rh(III) complexes of the type [Rh(COR)ClX(P,Se)] {where R = C2H5 (2a), X = I; R = CH2C6H5 (3a), X = Cl}, [Rh(CO)ClI2(P,Se)] (4a), [Rh(CO)(COCH3)ClI(P,Se)] (5b,d), [Rh(CO)(COH5)ClI-(P,Se)] (6b,d), [Rh(CO)(COCH2C6H5)Cl2(P,Se)] (7b,d) and [Rh(CO)ClI2(P,Se)] (8b,d). The kinetic study of the oxidative addition (OA) reactions of the complexes 1 with CH3I and C2H5I reveals a single stage kinetics. The rate of OA of the complexes varies with the length of the ligand backbone and follows the order 1a > 1b > 1c > 1d. The CH3I reacts with the different complexes at a rate 10,100 times faster than the C2H5I. The catalytic activity of complexes 1b,d for carbonylation of methanol is evaluated and a higher turnover number (TON) is obtained compared with that of the well-known commercial species [Rh(CO)2I2],. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Modular Chiral Bidentate Phosphonites: Design, Synthesis, and Application in Catalytic Asymmetric Hydroformylation Reactions

CHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2008
Baoguo Zhao Dr.
Abstract A new class of C2 -symmetric chiral bidentate phosphonite ligands has been synthesized in moderate to good yields from readily available starting materials. Application of these air-stable chiral phosphonites in the RhI -catalyzed asymmetric hydroformylation of styrene derivatives, vinyl acetate, and allyl cyanide afforded the corresponding chiral aldehydes with high regio- and enantioselectivities under mild reaction conditions. The modular nature of the ligands allows fine-tuning of the selectivities through judicious modifications of the substituents on the ligand backbone. X-ray structural analysis of the catalyst precursor suggested that the steric hindrance caused by the protruding remote substituents of the ligands into the vicinity of the metal center might be an important factor for the enantio-control of the reaction, whereas the sense of asymmetric induction can be rationalized on the basis of a trigonal-bipyramidal transition state diagram. [source]

Enantiospecific Syntheses of Copper Cubanes, Double-Stranded Copper/Palladium Helicates, and a (Dilithium),Dinickel Coronate from Enantiomerically Pure Bis-1,3-diketones,Solid-State Self-Organization Towards Wirelike Copper/Palladium Strands,

CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2008

Abstract Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subsequent Claisen condensation) chiral bis-1,3-diketones H2L(S,S) (3,a,c) with different substitution patterns. Reaction of these C2 -symmetric ligands with various transition-metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4,8 by diastereoselective self-assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transition-metal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)-[Cu4(L(S,S))2(OMe)4] (4,a,c) or dinuclear copper(II) helicates (P)-[Cu2(L(S,S))2] (5) could be synthesized with square-pyramidal and square-planar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double-stranded helical systems (P)-[Pd2(L(S,S))2] (6,7) were accessible exhibiting a linear self-organization of ligand-isolated palladium filaments in the solid state with short inter- and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H2L(S,S) (3,a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(Li,MeOH)2,{(,,,)-Ni2(L(S,S))2(OMe)2}] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self-assembly process in the systems 4,8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4,a and palladium(II) helicate 6. [source]