P₄²⁻: A 6π Aromatic Polyphosphide in Dicesium Cyclotetraphosphide–Ammonia (1/2)

Abstract

Aromatic P: Among the homoatomic polyanions of group 15 elements, Bi42− and Sb42− have been exotic curiosities for a long time, as they are potential 6π aromatic rings. As42− joined as the lighter congener as recently as 2002. Considering the diagonal relationship of P to C, the cyclobutadienediide analogue P42− would be expected naturally, but only now has it been prepared in the form of Cs2P4⋅2 NH3 from diphosphane(4).