PHOSPHINDOLIZINE - A COMPOUND WITH PLANAR PHOSPHORUS

Phosphindolizine, a fused ring with a bridgehead tricoordinated phosph orus, is nearly planar, with an inversion barrier of 3.5 kcal mol(-1) at the B3LYP/6-311 + G* level of theory. Diphosphaphosphindolizine is planar. Both the six- and the five-membered rings exhibit significant aromatic character, even in phosphindolizine, which is not entirely p lanar. The lone pair of the tricoordinate phosphorus is delocalized. T he estimated aromatic stabilization in the two rings is 40 kcal mol(-1 ).