Iron tetracarbonyl complexes of the biradicaloids [P(μ-N-Ter)]2 (Ter: 2,6-dimesitylphenyl) and [P(μ-C-IPr)]2 (IPr: 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) have been isolated. These two biradicaloids act here as σdonating, monodentate ligands. Experimental and theoretical data suggest that they can best be described in their zwitterionic resonance structures in these complexes. Single-crystal XRD and IR spectroscopy reveal that the donor strength of both is comparable to N-heterocyclic carbenes (NHCs). [P(μ-C-IPr)]2 is a slightly stronger donor than [P(μ-N-Ter)]2. Furthermore, an improved, scalable, and facile synthesis of both biradicaloids is presented.