Selective preparation of the [3,5-t Bu2-1,2,4-C2P3P]- ion and synthesis and the 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.