Question

what is a primary ligand and a secondary ligand?

Answer 1

Primary and secondary valence of coordination compound is there in the syllabus. Primary valency is the oxidation state of the metal and secondary valency is the coordination number. For ex.,
K₄[Fe(CN)₆] has oxidation state of iron as +2. This is the primary valency. Whereas secondary valency is the coordination number which is 6 here.

Primary ligands are the one which is directly attached to the metal atom. Whereas the secondary ligands are attached through the primary ligand. For ex in heteroleptic complexes,
K₃[Fe (H₂O) (Cl) (CN)_​4]. The water is the primary ligand and others are secondary ligand