plz explain as to how the two complex of , [ Ni(CN)₄]^-2 and Ni(CO)₄, have different structure , but donot differ in their magnetic behaviour .

In the complex [Ni(CN)₄] ^2- Nickel is in +2 oxidation state. Electronic configuration of Nickel is 3d⁸4s^2.

so, Ni²⁺ = 3d⁸

It will give square planar geometry with the hybridization dsp^2. The two electrons will be paired up in the d orbital because cyanide is a strong ligand.

While in case of [ Ni (CO)₄] Nickel is in the zero oxidation state.

so, Ni = 3d⁸4s²

Here CO is also a strong ligand so electrons will be paired and it will give tetrahedral structure with the hybridization sp³. Since all the electrons are paired in both the cases so their magnetic properties will be same that is they will be diamagnetic because in both the cases no electrons are unpaired.