The degree of CO₂ activation can be tuned by incorporating a distinct electronic coordination environment at the nickel center. A mononuclear nickel carboxylate species (Ni–CO₂, 3) and a dinuclear nickel–iron carboxylate species (Ni–CO₂–Fe, 5) were prepared. The structure of 3 reveals a rare η¹-κC binding mode of CO₂, while that of 5 shows bridging CO₂ binding (μ₂-κC:κ²O,O′) between the nickel and iron, presented as the first example of a nickel-μ-CO₂-iron species. The structural analyses of 3 and 5 based on XRD and DFT data reveal a higher degree of CO₂ activation in 5, imparted by the additional interaction with an iron ion.