A proton-triggered cascade reaction involving a heavy p-block multiple bond: Transformation of the diphosphene C5Me5P=PC 5Me5 into the cationic cage [C10Me 10P2H]⁺

Protonation of one of the phosphorus centers of the diphosphene C 5Me5P=PC5Me5 triggers a remarkable cascade reaction leading to the direct formation of a C10P 2 cage. Calculations suggest that the key mechanistic feature is the proximity of a C=C π-system to a developing positive charge on one of the phosphorus centers. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.