First cyclotrisiloxanes with three different R2Si-units of the general formula R2Si(OSiR2)(OSiR2)O (R2 = Me2Si(NSiMe3)2, R = Cl, Ot-Bu, R = Me) |
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Authors: | Andreas Rammo |
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Affiliation: | Institute of Inorganic Chemistry, Saarland University, Campus C4 1, 66123 Saarbrücken, Germany |
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Abstract: | The reaction of compound Me2Si(NSiMe3)2Si(OH)Cl with Me2SiCl2 leads to the disiloxane Me2Si(NSiMe3)2Si(Cl)OSi(Me2)Cl (1). Hydrolysis of 1 in the presence of pyridine results in Me2Si(NSiMe3)2Si(OH)OSi(Me2)OH (2), which is allowed to react with SiCl4 to give cyclotrisiloxane [Me2Si(NSiMe3)2Si](OSiMe2)(OSiCl2)O (3). The treatment of 1 with (t-BuO)2Si(OH)2 forms cyclotrisiloxane [Me2Si(NSiMe3)2Si](OSiMe2)[OSi(Ot-Bu)2]O (4). Compound 3 is obtained as a crystalline solid while 4 is an oily liquid. The ring size of these new types of cyclotrisiloxanes with three different R2Si-units is confirmed by cryoscopy in benzene, 29Si NMR chemical shifts and in case of 3, additionally by a single X-ray diffraction study. The different electronegativities of the substituents in the R2Si-units lead to different bond lengths and bond angles within the Si3O3 cycle, which are discussed in detail in the molecular structure of 3. |
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Keywords: | Cyclisations Siloxanes Cyclosiloxanes Cyclotrisiloxanes Silanols X-ray crystal structures |
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