AbstractWhite phosphorus (P4) undergoes degradation to P2moieties if exposed to the newN,N‐bis(silylenyl)aniline PhNSi21(Si=Si[N(tBu)]2CPh), furnishing the first isolable 2,5‐disila‐3,4‐diphosphapyrrole2and the two novel functionalized Si=P doubly bonded compounds3and4. The pathways for the transformation of the non‐aromatic 2,5‐disila‐3,4‐diphosphapyrrole PhNSi2P22into3and4could be uncovered. It became evident that2reacts readily with both reactants P4and1to afford either the polycyclic Si=P‐containing product [PhNSi2P2]2P23or the unprecedented conjugatedSi=P−Si=P−Si=NPh chain‐containing compound4, depending on the employed molar ratio of1and P4as well as the reaction conditions. Compounds3and4can be converted into each other by reactions with1and P4, respectively. All new compounds1–4were unequivocally characterized including by single‐crystal X‐ray diffraction analysis. In addition, the electronic structures of2–4were established by Density Functional Theory (DFT) calculations.