Oligosilanes systems

Many cyclic and linear transition metal-silicon compounds have been obtained by the elimination of alkali halides with the corresponding transition metal salts145,146. The synthesis and reactivity of the Fe-oligosilane systems have been studied in detail by Pannell147-154 and this area has been recently reviewed155. 

There are some silicon compounds with small Si-Si units linked together by Si-O-Si, Si-NH-Si or similar bond systems. In many cases, such compounds are obtained by the solvolysis of oligosilanes with a subsequent condensation reaction. However, preparation from polymeric starting material is also possible, for instance, the formation of siloxene from calcium silicide. 

Like the monosilane complexes, the oligosilanes form thermally and oxidatively stable complexes with the Re, Mn, Ru, and Fe systems, whereas the Mo complexes are significantly less stable. As yet such complexes have not been shown to exhibit any insertion-type reactions. The iron complexes... 

Miscellaneous Systems Many systems have been mentioned [li,m,2i] acyloxy and acylsilyl phosphine oxides, phosphine sulfides, cyclic compounds, benzoyloxa-ziridine derivatives, dibenzoylmethane derivatives, triazene and pentaazadiene moiety containing compounds. New developments include benzyl benzoin benzyl ethers [112], dithiocarbamates [113], ketoamides [114], phosphonates [115], bromo-acetylpyrene [116], alkylimides [117], aryloxy naphthalene [118], oligosilanes [119], bisphosphine sulfides [120], sulfamic esters of benzoin ethers [121], sulfur [122], or carbohydrate [123] containing compounds. 

Although the electronic resemblance between conjugated C-C n -bonds had been noticed a while ago it was only recently that single-molecule measurements of simple oligosilane chains were carried out which showed that the molecular conductance decreases exponentially with increasing chain length with a decay constant = 0.27 0.01 A comparable to that of conjugated Jt-systems [50]. 

CyclosUanes have always played a prominent role in the area of oligosilanes. Several reviews document the progress in this field [70, 71]. With the recognition of the fact that o-bond electrons in polysilanes can be delocalized in a similar way to conjugated Jt-systems, the question emerged whether cyclosUanes would exhibit properties... 

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