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Rh Complex (rh + complex)

Distribution by Scientific Domains

Polymers and Materials Science	85%

Selected Abstracts

Synthesis of Diastereomeric 1,4-Diphosphine Ligands Bearing Imidazolidin-2-one Backbone and Their Application in Rh(I)-Catalyzed Asymmetric Hydrogenation of Functionalized Olefins

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2005
Jian Zhang
Abstract The diastereomeric 1,4-diphosphine ligands, (S,S,S,S)- 1a, (R,S,S,R)- 1b and (R,S,S,S)- 1c, with the imidazolidin-2-one backbone were synthesized, and utilized for an investigation of the effects of backbone chirality on the enantioselectivity in the Rh(I)-catalyzed hydrogenation of various functionalized olefinic substrates. It was found that the catalytic efficiencies are largely dependent on the configurations of the ,-carbons to phosphine. Thus, the Rh complex of the pseudo- C2 -symmetrical diphosphine, (R,S,S,S)- 1c, showed excellent enantioselectivities (93.0,98.6% ees) in the hydrogenations of a broad spectrum of substrates, and especially in the hydrogenations of methyl ,-(N -acetyamino)-,-arylacrylates (95.3,97.0% ees). However, the enantioselectivities obtained with the C2 -symmetrical (R,S,S,R)- 1b were largely dependent on the substrate (19.8,97.3% ees). The Rh complex of ligand 1a having the (S,S,S,S)-configuration showed the lowest catalytic efficiency for all of the substrates examined (0,84.8% ees). [source]

Polymerization of substituted acetylenes by various rhodium catalysts: Comparison of catalyst activity and effect of additives

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2005
Atsushi Nakazato
Abstract This research deals with comparison of the activity of various Rh catalysts in the polymerization of monosubstituted acetylenes and the effect of various amines used in conjunction with [Rh(nbd)Cl]2 in the polymerization of phenylacetylene. A zwitterionic Rh complex, Rh+(nbd)[(,6 -C6H5)B,(C6H5)3] (3), was able to polymerize phenylacetylene (5a), t -butylacetylene (5b), N -propargylhexanamide (5c) and n -hexyl propiolate (5d), and displayed higher activity than the other catalysts examined, that is [Rh(nbd)Cl]2 (1), [Rh(cod)(O - o -cresol)]2 (2), and Rh-vinyl complex (4). Monomers 5a and 5c polymerized virtually quantitatively or in fair yields with all these catalysts, while monomer 5b was polymerizable only with catalyts 3 and 4. Monomer 5d did not polymerize in high yields with these Rh complexes. The catalytic activity tended to decrease in the order of 3 > 4 > 2 > 1. Although polymerization of 5a did not proceed at all in toluene with [Rh(nbd)Cl]2 alone, it smoothly polymerized in the presence of various amines as cocatalysts. The polymerization rate as well as the molecular weight of polymer depended on the basicity and steric bulkiness of amines. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4530,4536, 2005 [source]

Polymerization of substituted phenylacetylenes with a novel, water-soluble Rh,vinyl complex in water

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2004
Keiji Kanki
Abstract A novel, water-soluble Rh complex, (nbd)Rh[PPh2(m -NaOSO2C6H4)] [C(Ph)CPh2] (1) was synthesized by the reaction of [(nbd)RhCl]2, Ph2P(m -NaOSO2C6H4) and Ph2CC(Ph)Li, whose structure was determined by NMR and IR spectroscopies. The Rh catalyst 1 induced the polymerization of phenylacetylene (PA) in water to give two kinds of polymers; one was soluble in organic solvents such as tetrahydrofuran (THF) and CHCl3, and the other was insoluble in common organic solvents. The polymerization of sodium p -ethynylbenzoate (p -NaOCO-PA) homogeneously proceeded with 1 in water at 60 °C to give the polymer in high yield. Poly(p -NaOCO-PA) was treated with 1 N HCl and then reacted with (CH3)3SiCHN2 to obtain poly(p -MeOCO-PA). The methyl-esterified polymer was insoluble in THF and CHCl3, which suggests that the formed poly(p -MeOCO-PA) has cis,cisoidal structure. The polymer obtained from the polymerization of [p -CH3(OCH2CH2)2O2CC6H4]CCH with 1 in water was soluble in methanol, ethanol, and THF, and partly soluble in water. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2100,2105, 2004 [source]

Synthesis and Polymerization of Optically Active N -Propargylphosphonamidates: A Novel Helical Polymer Carrying a P-Chiral Center

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 17 2006
Dongmei Yue
Abstract Summary: A diastereomeric pair of novel N -propargylphosphonamidates, HCCCH2NHP(O)(CH3)O- L -menthyl was synthesized by the successive condensations of methylphosphonic dichloride with L -menthol and propargylamine. The (R)-P-isomer (1a) was isolated, and the absolute configuration was determined by XRD. Polymerization of 1a, and a mixture of 1a and (S)-P-isomer (1b) was carried out with a zwitterionic Rh complex as a catalyst. cis -Stereoregular polymers with number-average molecular weights of 5,600,9,800 were obtained in good yields. Poly(1a) and poly(1a29 - co - 1b71) exhibited large specific rotations (+408 and ,146°), and intense Cotton effects ([,],=,+2.25 and ,0.9,×,104 deg,·,cm2,·,dmol,1) based on the conjugated polyacetylene backbone around 325 nm in CHCl3, indicating that these polymers have helical structures, whose predominant helical senses are opposite. Polymerization of N -propargylphosphonamidate. [source]

Catalytic behavior of wool,Rh complex in asymmetric hydrogenation of 2-methyl furan,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3-5 2003
Man He
Abstract A Wool,Rh complex was prepared by the reaction of wool with RhCl3·3H2O in ethanol solution, and was found to be useful as a chiral catalyst for the asymmetric hydrogenation of 2-methyl furan to (S)-(+)-2-methyl tetrahydrofuran at 28,°C and under atmospheric hydrogen pressure. When an appropriate Rh content in the Wool,Rh complex was selected, the yield and optical yield amounted to 53.7 and 76.9%, respectively, and the Wool,Rh complex catalyst could be reused several times without any noticeable loss in its optical catalytic activity. Wool is a very cheap natural biopolymer ligand, and Wool,Rh complex is very easy to prepare, and it is a very active, enantioselective and stable chiral catalyst for asymmetric hydrogenation of 2-methyl furan. Copyright © 2003 John Wiley & Sons, Ltd. [source]