The 1:1 or 1:2 stoichiometric reaction of [Na2(thf)4(P4Mes4)] (1; Mes = 2,4,6‐Me3C6H2) with [{RhCl(cod)}2] (cod = 1,5‐cyclooctadiene) gave a mixture of compounds of which [Na(thf)3][Rh(P3Mes3)(cod)] (2) with a trimesityltriphosphane‐1,3‐diide ligand was structurally characterized. Density functional calculations on 2 confirmed the structural parameters obtained by X‐ray diffraction studies. Shared electron number and natural bond orbital analyses indicated only weak interactions between Na and P, which were found to be even weaker than the Na–Rh interactions with covalent contribution. When an excess of 1 was used (3:1 or 4:1), 2 was also obtained as the major product together with small amounts of the side‐products cyclo‐P6Mes6 (3) and [Na3(Et2O)(P4Mes4)(PHMes)]∞ (4). Compounds 3 and 4 were only characterized by single‐crystal X‐ray diffraction studies. Their formation indicates that the reaction includes the breaking and making of P–P bonds to give (P3Mes3)2–, PHMes–, and cyclo‐P6Mes6, although the mechanism is unclear. Furthermore, the reaction of 1 with 2 equiv. of [AgCl(PPh3)2] gave the tetranuclear compound [Ag4(P6Mes6)2] (5) in which the novel (P6Mes6)2– ion also indicates degradation of the P4 chain followed by P–P bond formation.