C2O42− is the oxalate ligand. It binds through two oxygen atoms and thus, is a bidentate ligand. Hence the co-ordination number of Fe in [Fe(C2O4)3]3− is 6 . SCN− is the thiocyanate ligand. It is a monodentate ligand. Hence the co-ordination number of Co in the complex ion [Co(SCN)4]2− is 4 .