Co-mediated Si-Si bond activation

Cobalt carbonyl compounds have been found useful in organic chemistry as protecting groups for alkynes, as catalyst for a number of interesting reactions and even as stoichiometric reagents (see f.i. cyclotrimerization of alkynes and the Pausen Khand reaction). In organosilicon chemistry cobalt complexed alkynylsilanes and even compounds containing silicon cobalt bond have been known for some while. Nevertheless, many aspects of the chemistry of these compounds have not even been addressed so far. In preliminary studies to this project a number of new cobalt complexed alkynyloligosilanes could be prepared. These compounds exhibited an unusually streng activation of Si-Si bonds within the oligosilyl fragment. This reactivity was responsible for the formation of a number of unexpected rearrangement products containing bridging silylene ligands. Within the framework of the planned project the chemistry of metal complexed alkynyloligosilanes will systematically be investigated. Especiall the Si-Si bond activation process, which is caused by the complexation will be studied in some detail. Also some focus will be put an the rearrangement process which is likely to be caused by the bond activation. Another rearrangement reaction which occurs when oligosilylhydrides are treated with dicobaltoctacarbonyl was observed. The structural similarty of the the rearrangement products obtained from the two reactions point at some related mechanisms. Investigations conceming the chemistry of cobalt carbonyl complexes with bridging silylene ligands will be another focus point of the planned research. Their structural similarity with dicobaltoctacarbonyl calls for the investigation of addition reactions to unsaturated substrates. Also further reactions with hydrosilanes and hydrogen may be of interest. In addition a screening for possible catalytic activity of the compounds will be carried out. Silylene transfer ability may be another potentially useful feature of these compounds. Finally, it should be made clear that all new compounds shall be investigated for their electrochemical, electronic and physical properies in -eneral, especially in light of possible interesting material properties.