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Titolo:
Preparation of new catalysts by the immobilization of palladium(II) species onto silica: An investigation of their catalytic activity for the cyclization of aminoalkynes
Autore:
Richmond, MK; Scott, SL; Alper, H;
Indirizzi:
Univ Ottawa, Dept Chem, Ctr Catalysis Res & Innovat, Ottawa, ON K1N 6N5, Canada Univ Ottawa Ottawa ON Canada K1N 6N5 Innovat, Ottawa, ON K1N 6N5, Canada
Titolo Testata:
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
fascicolo: 43, volume: 123, anno: 2001,
pagine: 10521 - 10525
SICI:
0002-7863(20011031)123:43<10521:PONCBT>2.0.ZU;2-W
Fonte:
ISI
Lingua:
ENG
Soggetto:
LIGAND-EXCHANGE REACTIONS; INTRAMOLECULAR HYDROAMINATION; OXIDATIVE-ADDITION; 2+2 CYCLOADDITIONS; COMPLEXES; ALKYNES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
28
Recensione:
Indirizzi per estratti:
Indirizzo: Alper, H Univ Ottawa, Dept Chem, Ctr Catalysis Res & Innovat, 10 Marie Curie, Ottawa, ON K1N 6N5, Canada Univ Ottawa 10 Marie Curie Ottawa ON Canada K1N 6N5 N 6N5, Canada
Citazione:
M.K. Richmond et al., "Preparation of new catalysts by the immobilization of palladium(II) species onto silica: An investigation of their catalytic activity for the cyclization of aminoalkynes", J AM CHEM S, 123(43), 2001, pp. 10521-10525

Abstract

Silica-immobilized palladium catalysts are readily prepared by treating partially dehydroxylated silica with solutions of the palladium(II) complexes, cis-[PdMeXL2] (X = Me, L-2 = dmpe; X = Cl, L-2 = dmpe, dppe, phen, bipy, 2PMe(3)), trans-[PdMeXL2] (X = Cl, NO3, OTf, L = PMe3; X = Cl, L = PPh3), or [PdPh(OH)L](2) (L = PPh3, PCy3), at room temperature. A chemisorption reaction is presumed to occur on the surface Si-OH groups, with elimination of1 equiv of methane, benzene, or water and the initial formation of a covalent Pd-O bond to the silica surface. The amount of chemisorbed material is strongly dependent on the nature of the complex employed, and the Pd content of the materials, determined by ICP analysis, was found to vary widely (from 1.47 to 0.021 wt %). It appears that the complexes stabilized by more basic ligands undergo a more facile reaction with the surface. The catalyticactivity of the materials was first tested in the cyclization of 6-aminohex-1-yne. Higher conversions were, found for those catalysts containing morebasic ligands, due to the higher loadings, and for those complexes containing more weakly coordinating anions. Silica/trans-[PdMe(NO3)(PMe3)(2)] was identified as the best catalyst and was used to test the generality of the catalytic cyclization method with two other alkynes, namely, 5-phenyl-4-pentyn-1-amine and 6-phenyl-5-hexyn-1-amine. The catalysts prepared here show rates comparable to, or greater than, those found for homogeneous late transition metal complexes, including their molecular precursors. Furthermore, the supported catalysts are only slightly air-sensitive and can be recycled, after filtration in air, with only moderate loss of activity.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 21/09/20 alle ore 06:17:23