Silicon tetraphenyl

Other examples of aromatic normal alkyls are the tetra-m-tolyl (m.p 151°)32 and the tetra-p-tolyl (m.p. 228°).33 Silicon tetra-benzyl34 more properly is grouped as an aliphatic compound, but it closely resembles silicon tetraphenyl in that it is a very stable substance of high melting point and exceedingly high boiling point (550°). 

Tetra-p-tolylsilicane, Si(C6H4CHg)4, is produced in the same way as silicon tetraphenyl, but using p-bromotoluene. It forms colourless, transparent crystals, M.pt, 228° C, density 1 0793 at 20° C., readily soluble in hot benzene and sparingly soluble in chloroform or ether. 

This liberation of energy by the reaction just shown was found by Schumb 4 and his coworkers also to be sufficient to cleave the silicon-silicon bond. The action of sodium on mixtures of ethyl bromide, chlorobenzene, or n-amyl chloride with hexachlorodisilane resulted only in tetrasubstituced monosilanes and no disilane derivatives. In the same way, the silicon-oxygen-silicon bond of hexachlorodisiloxane was split by sodium in the presence of ethyl bromide or chlorobenzene and yielded only silicon tetraethyl or tetraphenyl. 

The sul)stanee is isomorphoiis with the tetraphenyls of lead and silicon, and crystallises in prisms belonging to the tetragonal system,... 

Figure 31 The silicon tetrapyridone building block (host R) and the tetraphenyl borate building block (host S) discussed in the text.

Bigoh, R, Deplano, R, Mercuii, M.L. et al. (1991) A study on the donating properties of 4,5,6,7-tetrathiocino[l,2-h 3,4-h ]diimidazolyl-l,3,8,10-tetraphenyl-2,9-dithione(Ph4todit) towards iodine. Crystal and molecular structure of Ph4todit-CHCl3. Phosphorus Sulfur Silicon Relat. Elem., 62, 53-63. 

Cyclobutadiene dication, 61, is a 2jr-aromatic cation. In the carbon case, tetramethyl- and tetraphenyl-substituted derivatives of this dication were characterized in superacidic media already in 1976 [66]. A related persila-analogue, the tetrasilacyclobutadiene dication 62, was obtained only recently in an unexpected reaction between donor-stabilized silylene 63 and Cp ZrCl3. in 29% yield (Scheme 20) [67]. As an intermediate, a silicon(ll) cation, [LSi]", resulting from... 

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