Phosphaalkyne Cyclooligomers: From Dimers to Hexamers—First Steps on the Way to Phosphorus–Carbon Cage Compounds

Following the early successes of the di- and trimerization of 1 to give 2 and 3, respectively, the tetraphosphabarrelene 4 and the hexaphospha-p-[32,56]octahedrane 5 were synthesized recently. These and other more recent advancements in the field of PC cage compounds demonstrate once again the synthetic potential of tert-butylphosphaacetylene, which was prepared for the first time by Becker et al. in 1981.