Silenes and Disilenes

Over the last years the chemistry of unsaturated silicon compounds (disilenes, silenes, silylenes) has experienced a tremendous advancement. Stable examples of theses compounds have been obtained and their reactivity has been investigated. During our recent studies concerning the chemistry of polysilylanions we were able to establish two new routes to disilenes. In addition we have provided first examples of an early transition metal disilene complex and of a disilene fluoride adduct. In the proposal at hand the further elaboration of the mentioned chemistry is outlined. These studies shall be directed not only in terms of basic organosilicon research but also with respect to possible applications of disilenes and silenes and their adducts in organic synthesis. Depending on their substituents disilenes are able to undergo either [2+2] or [4+2] cyclo-addition reactions. The [4+2] Diels-Alder type reaction, which is predominant for silyl substituted disilenes can be considered as a synthetic equivalent to singlet oxygen addition. The silyl groups can function as masked hydroxyl equivalents which later can be set free by use of Tamao-Fleming oxidation chemistry. With respect to silenes it should be investigated if these can be obtained by salt elimination reactions from 1-carba- 2-silyl dianions. In analogy to the 1,2-disilanyl dianions it should also be studied if such compounds could be used for the synthesis of early transition metal silene complexes. The latter are supposed to exhibit interesting alkyne insertion chemistry to metallsilacyclopentenes. As we have discovered the very facile synthesis of disilene fluoride adducts from fluorosilanes, we want to investigate if we can use the same synthetic strategy for similar silene adducts. Such adducts are so far only known for Wiberg-type silenes. The obtained silenes (even if of transient nature) and their adducts shall also be studied for their use in cyclo- addition chemistry. The products of both silene and disilene cyclo-additions still contain Si-Si bonds. In the last parts of the project it should be studied how these reactive bonds can be utilized in a productive way for applications in organic synthesis.

Over the last years the chemistry of unsaturated silicon compounds (disilenes, silenes, silylenes) has experienced a tremendous advancement. Stable examples of theses compounds have been obtained and their reactivity has been investigated. During our recent studies concerning the chemistry of polysilylanions we were able to establish two new routes to disilenes. In addition we have provided first examples of an early transition metal disilene complex and of a disilene fluoride adduct. In the proposal at hand the further elaboration of the mentioned chemistry is outlined. These studies shall be directed not only in terms of basic organosilicon research but also with respect to possible applications of disilenes and silenes and their adducts in organic synthesis. Depending on their substituents disilenes are able to undergo either [2+2] or [4+2] cyclo-addition reactions. The [4+2] Diels-Alder type reaction, which is predominant for silyl substituted disilenes can be considered as a synthetic equivalent to singlet oxygen addition. The silyl groups can function as masked hydroxyl equivalents which later can be set free by use of Tamao-Fleming oxidation chemistry. With respect to silenes it should be investigated if these can be obtained by salt elimination reactions from 1-carba- 2-silyl dianions. In analogy to the 1,2-disilanyl dianions it should also be studied if such compounds could be used for the synthesis of early transition metal silene complexes. The latter are supposed to exhibit interesting alkyne insertion chemistry to metallsilacyclopentenes. As we have discovered the very facile synthesis of disilene fluoride adducts from fluorosilanes, we want to investigate if we can use the same synthetic strategy for similar silene adducts. Such adducts are so far only known for Wiberg-type silenes. The obtained silenes (even if of transient nature) and their adducts shall also be studied for their use in cyclo-addition chemistry. The products of both silene and disilene cyclo-additions still contain Si-Si bonds. In the last parts of the project it should be studied how these reactive bonds can be utilized in a productive way for applications in organic synthesis.