Which complex has a coordination number of 4 and is diamagnetic?
[Ni(CN)4]2− (Ni₂+, d8) with 4 strong field CN− ligands is square planar and diamagnetic (0 unpaired electrons).
Ref: NCERT Class 12 Chemistry > Chapter 5: Coordination Compounds > Topic: Werner's Theory and Definitions - Ligands Coordination Number