Do carbenes have a "hidden" carbon(0) character? Revisiting the electronic structure of 2,2'-bipyridyl carbene.

Density functional calculations predict that 2,2'-bipyridyl carbenes have some degree of "hidden" carbon(0) character. This is supported by very high second proton affinity values and bond dissociation energies (BDEs) for the dissociation of one AuCl and one Ni(CO)(2) molecule from [(AuCl)(2)(2,2'-bipyridyl carbene)] and [{Ni(CO)(2)}(2)(2,2'-bipyridyl carbene)]. An Arduengo type carbene also showed significant BDE values for gem-dimetallation, thus indicating the possible existence of carbon(0) character. All of the dimetallated derivatives showed metallophilic interactions.