Conformational Control of Polysilanes: Use of CH2 Spacers in the Silicon Backbone
By the reaction of a number of oligosilyl potassium compounds with (trimethylsilyl)chloromethane, derivatives containing the (trimethylsilyl)methyl substituent were prepared. Using X-ray single-crystal structure analysis and UV spectroscopy the conformational properties of some of the compounds were studied. It was found that the (trimethylsilyl)methylated examples exhibit UV absorption properties which correspond to lower energy transitions in comparison to those of analogous trimethylsilylated molecules. The influence of this effect decreases, however, with increasing chain lengths.
Rearrangement/Fragmentation Reactions of Oligosilanes with Aluminum Chloride
Reinvestigation of the Lewis acid catalyzed rearrangement of some open-chain permethyloligosilanes with the Al(Fe)Cl3 catalyst system exhibited several cases of additional reactivity: namely, a fragmentation/cyclization reaction. Introduction of (trimethylsilyl)methyl substituents into the oligosilane substrates strongly facilitated this reaction, yielding cyclic or bicyclic carbacyclosilanes. Investigations concerning the composition of the catalyst system indicated that the incorporation of about 0.1% FeCl3 into the AlCl3 lattice provided an effective catalyst.
Hexakis(trimethylsilyl)disilane: A highly branched and symmetrical organopolysilane
Abstract Hexakis(trimethylsilyl)disilane (1), a novel, highly branched and symmetrical polysilane, was synthesized by a number of procedures. Many of these gave (I) in only 5–9% yield. The reaction of tris(trimethylsilyl)silyllithium (II) with 1,2-dibromoethane ( ca .-70°) gave (I) in 45–50% yields, and proved to be the most satisfactory method of synthesis. The physical and spectral properties of (I) are discussed. Lithium and methyllithium reacted with (I) to cause cleavage of the symmetrical Si Si bond, while (II), triphenylsilyllithium and halogens effected cleavage of peripheral trimethylsilyl groups.