Reactivity of functionalized diphosphiranes and 1,3-diphosphapropenes towards Grignard reagents

The reaction of saturated and unsaturated organomagnesium compounds with the monohalogenated diphosphiranes, 1a-b, and their isomers, the 1,3-diphosphapropenes, 2a-b, leads to a series of substituted 1,3-diphosphapropenes and 1,3-diphosphadienes 4-8 (a-b), but with the dihalogeno-derivatives 1c-d and 2c-d, it gives quantitative yields of 1,3-diphospha-allene 9. The reaction occurs via an anionic ring-opening involving an allylic anion intermediate 11a-b, detected by 31 P NMR.