(L) 2 C 2 P 2 : Dicarbondiphosphide Stabilized by N‐Heterocyclic Carbenes or Cyclic Diamido Carbenes

Carbon phosphides, C n P m , may have highly promising electronic, optical, and mechanical properties, but they are experimentally almost unexplored materials. Phosphaheteroallenes stabilized by N‐heterocyclic carbenes undergo a one‐electron reduction to yield compounds of the type (L) 2 C 2 P 2 with diverse structures. The use of imidazolylidenes as ligands L give complexes with a central four‐membered ring C 2 P 2 , while more electrophilic cyclic diamidocarbenes (DAC) give a compound with an acyclic π‐conjugated CP−PC unit. Cyclic C 2 P 2 compounds are best described as non‐Kekulé molecules that are stabilized by coordination to the NHC ligands NHC→(C 2 P 2 )←NHC. These species can be easily oxidized to give stable radical cations [(NHC) 2 C 2 P 2 ] +. . The remarkably stable molecules with an acylic C 2 P 2 core are best described with electron‐sharing bonds (DAC)=C=P−P=C=(DAC).