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Titolo:
Steric factors affecting the Bronsted acidity of aluminosilsesquioxanes
Autore:
Skowronska-Ptasinska, MD; Duchateau, R; van Santen, RA; Yap, GPA;
Indirizzi:
Eindhoven Univ Technol, Schuit Inst Catalysis, Dutch Polymer Inst, NL-5600MD Eindhoven, Netherlands Eindhoven Univ Technol Eindhoven Netherlands NL-5600 MD ven, Netherlands Univ Ottawa, Ottawa, ON K1N 6N5, Canada Univ Ottawa Ottawa ON Canada K1N 6N5 v Ottawa, Ottawa, ON K1N 6N5, Canada
Titolo Testata:
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
fascicolo: 1, , anno: 2001,
pagine: 133 - 137
SICI:
1434-1948(200101):1<133:SFATBA>2.0.ZU;2-V
Fonte:
ISI
Lingua:
ENG
Soggetto:
POLYHEDRAL ALUMINOSILSESQUIOXANES; ALUMINOSILICATES; FRAMEWORKS; CHEMISTRY; ZEOLITES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
20
Recensione:
Indirizzi per estratti:
Indirizzo: Skowronska-Ptasinska, MD Eindhoven Univ Technol, Schuit Inst Catalysis, Dutch Polymer Inst, POB 513, NL-5600 MD Eindhoven, Netherlands Eindhoven UnivTechnol POB 513 Eindhoven Netherlands NL-5600 MD
Citazione:
M.D. Skowronska-Ptasinska et al., "Steric factors affecting the Bronsted acidity of aluminosilsesquioxanes", EUR J INORG, (1), 2001, pp. 133-137

Abstract

By reacting AlMe3 with two equivalents of (c-C5H9)(7)Si7O9(OH)(2)OSiR3, the corresponding Bronsted acidic aluminosilsesquioxanes [(c-C5H9)(7)Si7O11(OSiR3)]Al[(c- C5H9)(7)Si7O10(OH)OSiR3] [SiR3 = SiMe3 (1a), SiMePh2 (1b)] areobtained. These complexes readily react with triethylamine to yield the corresponding ammonium salts {[(c-C5H9)(7)Si7O11(OSiR3)](2)Al}(-)(HNEt3)(+) (2a,b). Hydrogen bonding between the acidic SiO(H)-->Al proton and the pendant silyl ether function is effectively reduced by increasing the steric bulk of the silyl ether substituents, resulting in a higher acidity for 1b compared to that of 1a. With the silsesquioxane ligand (c-C5H9)(8)Si8O11 (OH)(2), which lacks pendant silyl ether functions, the acidic proton cannot satisfactorily be stabilized and this renders the putative Bronsted acid [(c-C5H9)(8)Si8O13]Al[(c-C5H9)(8)Si8O12(OH)] unstable. In the absence of proton accepters, the disproportionation product [(c-C5H9)(8)Si8O13](3)Al-2 (3) isformed instead of the Bronsted acid. However, in the presence of triethylamine, the initially formed Bronsted acid readily transfers its proton to the amine, affording the ammonium salt {[(c-C5H9)(8)Si8O13](2)Al}(-){HNEt3}(+) (4).

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 14/07/20 alle ore 06:49:21