[luketapis]

Hi I have a question:

Which of the following complexes is the more likely to be tetrahedral; [Ni(CN)4]2- or [NiCl4]2-

They are both d8 Cl^- is small ligand so it gives high spin. So is that specie going to be tetrahedral?
BTW I thought that Coordination No.= 4 and d8 gives squer planar.

[kaliaden]

Ni2+ can form both square planar and tetrahedral complexes with coordination 4.
With strong ligands like CN, it forms square planar complexes. However, with some weak ligands like Cl-, Br-, I- it forms tetrahedral complexes since the splitting energy is small.

But other elements with d8 configuration like Pd2+ and Pt2+ form only square planar complexes.