Phosphasilenes with sulfur

The oxidation of the phosphasilenes 12a and 15a with elemental sulfur and tellurium led the corresponding chalcogen heterocycles 23 (Eqs. 7,... 

As mentioned in this chapter, in recent years much progress has been made in the chemistry of silicon-chalcogen multiple bonds. For silicon-sulfur doubly-bonded compounds, we have now several isolated examples, both kinetically stabilized and thermodynamically stabilized. Furthermore, there have been reports of the synthesis and characterization of stable compounds with silicon-nitrogen double bonds (i.e. silanimines or iminosilanes) as well as their heavier group 15 element analogues such as phosphasilenes and arsasilenes. 

Phosphasilenes RR Si=PR", wherein the substituents are bulky stabilizing groups, are also known. Addition across the Si-P double bond with concomitant cycle formation can be achieved by many species including nitriles, sulfur, and phosphorus itself... 

---