(L)2C2P2: dicarbondiphosphide stabilized by N-heterocyclic carbenes or cyclic diamido carbenes

Carbon phosphides, C P , 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) C P with diverse structures. The use of imidazolylidenes as ligands L give complexes with a central four-membered ring C P , while more electrophilic cyclic diamidocarbenes (DAC) give a compound with an acyclic π-conjugated CP-PC unit. Cyclic C P compounds are best described as non-Kekulé molecules that are stabilized by coordination to the NHC ligands NHC→(C P )←NHC. These species can be easily oxidized to give stable radical cations [(NHC) C P ] . The remarkably stable molecules with an acylic C P core are best described with electron-sharing bonds (DAC)=C=P-P=C=(DAC)