Tetrasilatetrahedranes synthesis

Recently, some attention has been focused on the synthesis and on the properties of strained cage compounds made up exclusively of Si atoms. As a consequence a number of derivatives of tetrasilatetrahedrane, hexasilaprismane and octasilacubane have been synthesized. The current knowledge in the field up to 1994 has been summarized... 

The only known example of the tetrasilatetrahedrane molecule, tetrakis(tri-terf-butylsilyl)tetrasilatetrahedrane 1, was reported by Wiberg in 1993 by the reaction of f-Bu3Si—SiBr2—SiBr2—Si(Bu-f)3 with f-Bu3SiNa in THF at — 20°C16. The details of its synthesis as well as its physico-chemical characteristics are summarized in a recent review14 and will not be considered in the present article. 

The synthesis of the title compound was reported several years later by the same authors, who had previously prepared tetrasilatetrahedrane in a similar way. Thus, f-BusSi—GeCl2—GeCl2—Si(Bu-f)3, which was prepared by the reaction of GeCLj and f-Bu3SiNa in THF at room temperature, was reacted with f-Bu3SlNa in THF at —78°C. The tetragermatetrahedrane 2 was formed in a low yield together with some other products (Scheme 1). 

Tetrasilatetrahedrane is accessible if the appropriate substituent is selected. As found in the case of the octasilacubane (/frr-BuMe2SiSi)s (15), silyl substituents decrease the strain in the polyhedrane (14). Thus, the synthesis of tetrasilatetrahedrane has been accomplished by use of the supersilyl group (/ert-BusSi) (10). 

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