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Title: Stable partially substituted silicon clusters from functional disilenes and homo- and heterocyclic silanes
Author: Abersfelder, Kai Helmut
ISNI:       0000 0004 2728 9799
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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Disilenides, i.e. disila analogues of vinyl anions as an example for functionalized disilenes, are well-suited to transfer a Si-Si double bond moiety to a broad variety of organic and inorganic substrates. During this project different aspects of disilenide reactivity were investigated. On the one hand, the stable disilenes thus obtained allow the study of the properties of unsymmetrically substituted Si-Si double bonds. Examples synthesisied during this project include silyl- and stannyl substituted disilenes. In particular, the relatively weak Si-Sn bond may be useful for further functionalisation. On the other hand, the high tendency of the Si-Si double bond towards rearrangements into saturated structures was used for the preparation of otherwise inaccessible (multi)functional homonuclear silicon rings, which turned out to be well-suited precursors for the synthesis of partially substituted molecular silicon clusters. The main part of this thesis focuses on such metalloid silicon cluster compounds. Metalloid clusters are compounds which contain one element in different oxidation states with an average oxidation state between 0 and 1 and can be regarded as intermediate species between organometallic molecules and the elemental state. In particular, silicon derivatives are of interest as similar species are assumed intermediates in gas phase deposition techniques and furthermore band-gap determining constituents of amorphous silicon modifications produced via these techniques. The stable compounds that were obtained and fully characterised include an aromatic tricyclic isomer of hexasilabenzene and a bridged persilapropellane, which turned out to be a substituted derivative of the global minimum on the potential energy surface of Si6H6. Both compounds show the rare structural feature of unsubstituted cluster vertices. Reactivity studies on these clusters were carried out including the stepwise halogeneration, reduction and reaction with organometallic reagents. From the reaction with halogenating agents functionalised silicon clusters were obtained.
Supervisor: Britovsek, George Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral