The 2-phosphaethynolate anion: a convenient synthesis and [2+2] cycloaddition chemistry.

Hip to be square: Direct carbonylation of solutions of the heptaphosphide trianion (P7(3-)) afforded the phosphaethynolate anion in moderate yields. This species undergoes [2+2] cycloaddition reactions with diphenylketene and bis(2,6-diisopropylphenyl)carbodiimide to yield the anionic four-membered heterocycles P[C(O)]2C(C6H5)2(-) and PC(O)(CNDipp)NDipp(-)