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Low valent iron complexes bearing bis(amidine)pyrimidylidene (or carbeno-diamidine, CDA) ligands have been synthesized and characterized by X-ray crystallography, Mössbauer spectroscopy, infrared spectroscopy, EPR spectroscopy, and DFT calculations. One electron reduction of (CDA)FeCl2 (1) resulted in formation of (CDA)FeCl (2), which demonstrated an unusual metal−N-heterocyclic carbene (NHC) interaction where a redox-noninnocent NHC participates in a one electron π-interaction with the metal center. This interaction renders the complex best described as a low spin iron(II) complex that is antiferromagnetically coupled to a singly reduced CDA ligand. Two electron reduction of 1 under an atmosphere of carbon monoxide resulted in the formation of the diamagnetic complex (CDA)Fe(CO)2 (3). Complex 3 demonstrated significantly lower CO stretching frequencies compared to previously reported bis(imino)pyridine and even bis(N-heterocyclic carbene)pyridine iron complexes, which reflects the significant σ-donating capabilities of the CDA ligands.