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Synthesis 2004(16): 2727-2735  
DOI: 10.1055/s-2004-831246
PAPER
© Georg Thieme Verlag Stuttgart · New York

Tri(ethylene Glycol)- and Poly(ethylene Glycol) Ether End-Grafted Carbo­siloxane and Carbosilane Dendrimers: Synthesis and Reaction Behavior

R. Buschbeck, S. Mecklenburg, B. Lühmann, V. K. Gupta, H. Lang*
Technische Universität Chemnitz, Fakultät für Naturwissenschaften, Institut für Chemie, Lehrstuhl Anorganische Chemie, Straße der Nationen 62, 09111 Chemnitz, Germany
Fax: +49(371)5311833; e-Mail: heinrich.lang@chemie.tu-chemnitz.de;
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Publikationsverlauf

Received 23 June 2004
Publikationsdatum:
29. September 2004 (online)

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Abstract

The preparation of TEG- [tri(ethylene glycol) mono­methyl ether] and PEG- [poly(ethylene glycol) monomethyl ether] terminated carbosiloxane and carbosilane dendrimers of the 1st-3rd generation is discussed. Alcoholysis of Si(OCH2CH2CH2SiMe­XCl)4 (1a, X = Me; 1b, X = Cl) with HO(CH2CH2O)nMe (2a, n = 3, TEG; 2b, n = 7.3, PEG) gives the appropriate dendrimers Si[OCH2CH2CH2SiMe2O(CH2CH2O)nMe]4 (3a, n = 3; 3b, n = 7.3) and Si{OCH2CH2CH2SiMe[O(CH2CH2O)nMe]2}4 (4a, n = 3; 4b, n = 7.3). In an analogous manner the 2nd and 3rd generation carbosiloxane dendrimers Si(OCH2CH2CH2SiMe{OCH2CH2CH2Si­Me[O(CH2CH2O)nMe]2}2)4 (6a, n = 3; 6b, n = 7.3) and Si[OCH2CH2CH2SiMe(O(CH2)6SiMe{OCH2CH2CH2SiMe[O(CH2CH2O)3Me]2}2)2]4 (8) are accessible. The preparation method for 3, 4 and 6 can successfully be transferred to Si(CH2CH2CH2SiMeCl2)4 (9) and Si[CH2CH2CH2SiMe(CH2CH2CH2SiMeCl2)2]4 (11). The carbosilane dendrimers Si{CH2CH2CH2SiMe[O(CH2­CH2O)nMe]2}4 (10a, n = 3; 10b, n = 7.3) and Si(CH2CH2CH2­SiMe{CH2CH2CH2SiMe[O(CH2CH2O)3Me]2}2)4 (12) are obtained in very good yield. However, the Si-O bonds in 3, 4, 6, 8, 10 and 12 may be cleaved in the presence of a protonic source. Therefore, the carbosilane dendrimers Me2Si[CH2CH2CH2SiMe2CH2CH2­CH2O(CH2CH2O)3Me]2 (15), Si[CH2CH2CH2SiMe2CH2CH2­CH2O(CH2CH2O)3Me]4 (17) and Si{CH2CH2CH2SiMe[CH2CH2-CH2SiMe2CH2CH2CH2O(CH2CH2O)3Me]2}4 (19) were synthesized by the hydrosilylation of CH2=CHCH2O(CH2CH2O)3Me (14) with Me2Si(CH2CH2CH2SiMe2H)2 (13), Si(CH2CH2CH2SiMe2H)4 (16) or Si[CH2CH2CH2SiMe(CH2CH2CH2SiMe2H)2]4 (18) in the presence of the Karstedt catalyst. ESI-TOF MS studies reveal that 3a, 10a, 12, 15, 17 and 19 form complexes with Na+ and K+ cations, which enables such species as possible ionophores for chemical sensors.

Key words

carbosilane dendrimers - carbosiloxane dendrimers - chemical sensors - poly(ethylene glycol) monomethyl ether - tri(ethylene glycol) monomethyl ether