Adducts of the dinitrosyl iron unit and mono-nitrosyl bis-mercaptoethanediazacycloheptane (bme-dach) iron and cobalt are described in terms of the (bme-dach)M(NO) as metallodithiolate ligands. With M = Fe, a diamagnetic (N2S2)Fe(NO)·Fe(NO)2 diiron complex, in which the (N2S2)Fe(NO) unit serves as a bidentate ligand to the Fe(NO)2 unit is derived by use of a trinitrosyliron cation as precursor to the DNIC unit as well as a NO source to cleave the [(bme-dach)Fe]2 dimer (J. Am. Chem. Soc., 2010, 132, 14118). By a similar approach of [(bme-dach)Co]2 dimer cleavage, the Co–Fe bimetallic contains (N2S2)Co(NO) as a monodentate metallothiolate ligand to Fe(NO)2L, L = I-Mes, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene. Characterization of this paramagnetic cation includes infrared and EPR spectroscopies, and X-ray diffraction analysis. The latter finds a Co⋯Fe distance of 3.697 Å in contrast to the Fe–Fe bond distance of 2.7857(8) Å in the homobimetallic complex.