Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

Building pyramids: The first P–C cluster, namely, the novel nido species 2, is readily prepared from 1 (•=CtBu), which is also an excellent precursor for the selective synthesis of the anion 3. DFT calculations show that there is a switch in the global minimum, on the introduction of three P atoms (CH) into the [C5H5]+ ion, from cyclic-unsaturated to saturated cage species, such as 2.