Carbenes and radicals are among the most important reactive intermediates.[1] However, very little is known about their cross-reaction—the addition of a radical to a carbene to yield a new radical. This is mainly due to the generally short lifetime of these species which normally prevents the build up of sufficiently high concentrations of both species in the same reaction vessel. This situation has changed with the synthesis of stable carbenes 1.[1b] Yet, except for a single study on the addition of a muonium to 1,[2] very little is known on this fundamentally important reaction. To study such reactions the correct type of radicals has to be used. Radicals (YC) need to be chosen so that in the adduct radicals the unpaired electron can interact with adjacent magnetically active atoms to provide useful EPR data. Thus, we chose the dialkoxyphosphoryl radical 2a and the metal-centered radicals 2b–2d as YC [Eq.(1)].