Skeletal Rearrangement Process in Organometallic Cations of Group 14 Elements - A Powerful Concept for Assembling Complex Polysilane Frameworks

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Despite the highly interesting electronic properties and the technological potential of polysilanes the chemist’s repertoire for their synthesis or structural manipulation is mostly limited to the Wurtz type coupling reaction. In this connection Lewis acid catalyzed rearrangement reactions represent an interesting method to access molecular structures, which are otherwise difficult to obtain. Closely related to the well know Wagner-Meerwein rearrangement, it is a much more facile process for polysilanes. Although first examples of polysilane rearrangement have been reported almost 40 years ago not much is known about the governing principles of this reaction. The current project, to be carried out by the groups in Oldenburg and Graz, proposes a joint study comprising new synthetic approaches, investigations of intermediates and reaction mechanisms, both supported by computational methods. Preliminary studies have already shown that the reaction of isomeric polysilanes with aluminum chloride can result in the formation of rather complex structures such as an adamantane type tricyclic polysilane. In addition it was found that germanium containing polysilanes rearrange with the germanium atoms selectively moved to trisilylated positions of the product.Other preliminary results suggest the Lewis acid catalyzed reaction can also be used for the synthesis of polysilanes containing alkylene units and even further for the preparation of complex carbosilanes. The synthetic work in this project, conducted by the Austrian group, will benefit from the theoretical and basic studies (of the German group) which will provide insight into the underlying principles of the chemistry. On the other hand will the synthetic work allow formulating new questions which will be addressed by computational methods. The unique combined synthetic and theoretical expertise of the two groups will allow the best possible treatment of the complex matter of Lewis acid catalyzed rearrangement reactions.