Sodium polyphosphides Na x P n (Na cyclo ‐P 5 and Na 3 P 7 ), generated from white phosphorus and elemental sodium, react with phosphaalkynes R–C≡P (R = SiMe 3 , t Bu, Ad, Mes) to give the respective sodium 2,5‐R‐1,3,4‐triphosphacyclopentadienide Na1,3,4‐( cyclo ‐(CR) 2 P 3 either solely, or as a mixture with the corresponding 1,2,3,4‐tetraphosphacyclopentadienide Na( cyclo ‐(CR)P 4 . The one‐pot reaction between Na, P 4 , and carboxylic acid derivatives (acyl chlorides or esters) leads to a mixture that mainly consists of sodium bis(acyl)phosphides Na(C(O)R) 2 P and 1,2,3,4‐tetraphosphacyclopentadienides Na( cyclo ‐(CR)P 4 (R = Ar, Alk, ), which can be separated. ( cyclo ‐(CR)P 4 – anions represent a class of scarcely investigated aromatic phosphorus‐heterocycles that are of considerable interest in coordination chemistry. Further studies show the possibilities to generate tetraphosphaferrocenes when treated with Fe II precursors.
Ernst et al. (2026) studied this question.