[Ni(CN)4]2−:d8 configuration, SFL, sq. planar splitting (dsp2), diamagnetic.
[Ni(CO)4]:d10 config (after excitation), SFL, tetrahedral splitting (sp3), diamagnetic.
[NiCl4]2−:d8 config, WFL, tetrahedral splitting (sp3), paramagnetic (2 unpaired e−).
[Ni(CN)4]2– is square planar and diamagnetic with
μ=0
its hybridisation is dsp2
[Ni(CO)4] is tetrahedral but diamagnetic