A Facile Access to 1λ⁵, 3λ⁵‐Benzodiphospholes

The first PV–CR = PV species with a five-coordinate and a four-coordinate phosphorus atom, the title compound 1 in which R is CH3 or PhC = CHPh, for example, were synthesized from 1,3-diphosphaallyl cations and sodium hexamethyldisilazanide. Its “central” C atom has ylidic character. On heating the benzodiphospholes 1, a phosphorane–phosphane rearrangement takes place.