Coordination chemistry at carbon: The patchwork family comprising (Ph ₃P)₂C, (Ph₃P)C(C₂H₄), and (C₂H₄)₂C

The revitalized concept of "coordination at carbon" allows relationships between seemingly unrelated families of carboncentered compounds to be discovered generating fascinating patchwork families of compounds. It is shown how olefins and cyclopropanes can be regarded as donors for carbon acceptors C₁, ₂, and ₃. Through this approach, hydrocarbons such as spiropentane and dicyclopropylidene are found to be counterparts of the bis-ylidic carbodiphosphoranes and the corresponding mixed mono-ylidic systems.