YLIDYL 1,2,4-THIADIPHOSPHETANE AND 1,2,4-SELENADIPHOSPHETANE SULFIDESAND SELENIDES

Phosphoniumylidyl thioxophosphanes and selenoxophosphanes, the only kn own monomeric chalcogenoxophosphanes, react in a 2:1 ratio with triphe nylphosphonium ylides. With loss of PPh(3) the 1,2,4-thia(or selena)di phosphetane monosulfides (or selenides) are formed. Their prominent st ructural feature are the very different PS bond lengths in the ring. T hey can be oxidized to the corresponding disulfides or sulfide selenid es. The latter rearrange to the isomer in which the selenium atom has become a ring member.