Silylated heptaphosphanes and heptaarsanes

The project envisages the synthesis of heptaphosphanortricyclenes P7 R3 with sterically demanding oligosilyl substituents R such as -Si(SiMe 3 ) 3 , -Si(SiMe 3 ) 2 Si(SiMe 3 ) 3 or -SiMe2 Si(SiMe 3 ) 3 , as well as germyl and stannyl substituents such as Ge(SiMe3 ) 3 and Sn(SiMe3 ) 3 . The heptaphosphanes will be prepared from red phosphorus, sodium/potassium alloy and the halogenated oligosilanes ClR. Various reactions of the heptaphosphanortricyclenes P7 R3 will be investigated, attempting the synthesis of functionalized cages P7 R2 X and P7 RX 2 with X an alkaline metal, a halogen or hydrogen. Reactions of these functionalized cages will be investigated. SiSi-bonds of oligosilyl groups can be cleaved at temperatures as low as -60 degrees Celsius, with comcomitant formation of silylenes or disilenes. Therefore, silylenes and disilenes will be generated from the cages by reaction with tertiarybutyl potassium oxide, and insertion reactions into phosphorus phosphorus bonds will be studied.

In the project, heptaphosphanes P7 (SiR 3 ) 3 with silyl groups of varying size were synthesized, and their reactivities and stabilities have been investigated. It was found that with increasing size of SiR 3 (for instance for Si(SiMe 3 ) 3 oder SiMe(SiMe3 ) 2 ) unusual substitution patterns on the P7 -backbone could be stabilized. Derivatives such as P7 (SiR 3 ) 2 H and P7 (SiR 3 ) 2 X with X = Cl, Br, I as well as anionic species such as [P 7 (SiR 3 ) 2 ] - and [P 7 SiR 3 ] 2- could be synthesized successfully and could be characterized with X-ray crystallography. Moreover, oligosilyl substituted derivatives such as P7 [Si(SiMe3 ) 3 ] 3 could be prepared in a simple manner by silyl exchange between P7 (SiMe3 ) 3 and ClSi(SiMe 3 ) 3 .