Reactions of a Cyclotrisilane with Chalcogen Transfer Reagents
Treatment of hexa-tert-butylcyclotrisilane (1) with Et3PTe afforded the telluratrisiletane 5 in high yield. Irradiation of 1 in the presence of phenyl isothiocyanate furnished the l,4-dithia-2,5-disilacyclohexane-3,6-diimine ring compound 6. The structure
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Fachbereich Chemie, Universitiit Oldenburg, D-26111 Oldenburg, Germany Max-Planck-Institut fi.ir Festkorperforschung, D-70506 Stuttgart, Germany
Summary. Treatment of hexa-tert-buty1cyc1otrisilane (1) with Et3PTe afforded the telluratrisiletane 5 in high yield. Irradiation of 1 in the presence of phenyl isothiocyanate furnished the 1,4-dithia-2,5disilacyc1ohexane-3,6-diimine ring compound 6. The structures of 5 and 6 were determined by X-ray crystallography. Keywords. Silicon; Cha1cogens; Silaheterocyc1es. Reaktionen eines Cyclotrisilans mit Chalkogen-Transfer-Reagentien [1] Zusammenfassung. Einwirkung von Et3PTe auf Hexa-tert-buty1cyc1otrisilan lieferte das Telluratrisiletan 5 in hoher Ausbeute. Belichten von 1 in Gegenwart von Phenylisothiocyanat ergab das 1,4-Dithia-2,5-disilacyclohexan-3,6-diimin-Ringsystem 6. Der Aufbau von 5 und 6 wurde durch Rontgenstrukturanalysen gesichert.
Introduction Cyclotrisilanes are the smallest and at the same time the most recently discovered representatives of the cyclooligosilanes [2]. The strain within the three-membered ring system is reflected by two typical reaction modes [3]. Under protection from light or in the absence of a catalyst, cleavage of one Si-Si bond occurs to give, depending on the type of the reaction partner, either open-chain trisilanes or ring expansion products. On the other hand, exposure to light results in the synchronous cleavage of two Si-Si bonds to furnish a silylene and a disilene, species which have been characterized by numerous trapping reactions.
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Corresponding author
U. Schubert (ed.), Silicon Chemistry © Springer-Verlag Wien 1999
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4, X=S, Se
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M. Weidenbruch et al.
The behaviour of hexa-tert-butylcyclotrisilane (1) has been investigated widely; for example, it reacts with sulfur or selenium to furnish the ring expanded thia- or selenatrisiletanes 4. In contrast, so far no reaction has been observed with tellurium [4]. Di-tert-butylsilylene (2) and tetra-tert-butyldisilene (3) are formed under photolytic conditions and undergo secondary addition reactions with various multiple bond systems to yield a wide variety of three- or higher membered ring systems [3]. We now report on the formation of a previously unknown telluratrisiletane as well as the photochemical reaction of 1 in the presence of pheny lisothiocyanate.
Results and Discussion Although 1 does not react with tellurium alone, addition of a small amount of triethylphosphane to a mixture of the components gives rise to a reaction, recognizable on account of the change in colour from yellow to colourless, which is complete within 90 minutes. tBu2Si--Te 1 + Et3PTe
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I I
tBu2Si--SitBu2 5
The NMR spectroscopic characterization of the colourless, crystalline telluratrisiletane 5 turned out not to be easy since the I H NMR spectrum surprisingly contained only one signal for the methyl protons. However, the 13e NMR spectrum revealed two sets of signals for the primary and the quaternary carbon atoms. The 29Si-NMR spectrum furnished more information in the form of two
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