oxalate ion (ox) [Ni(ox)2]2- .
phenanthroline (phen) cis-[Rh(phen)2Cl2]+
Phenanthroline, an aromatic hydrocarbon, is a neutral molecule containing two donor N atoms.
For the cationic complex, cis-[Rh(phen)2Cl2]+, two phenanthroline molecules are bonded to the central Rh ion one of the phenanthroline molecules bonds through one equatorial bond and one axial bond while the second bonds through two equatorial bonds. If both phen groups had been bound equatorially, the chloro groups would have been trans to each other.
acetylacetonate ion (acac) [Cr(acac)3]3+
Acetylacetonate ion makes two coordinate bonds one with each of the two oxygen donor atoms.
Three acetylacetonate ions are bonded to the Cr atom, forming three 5-membered rings. The CN of 6 for the tris(acetylacetonate)chromium (III) cationic complex results in an octahedral geometry.
Other Bidentate Ligands
2,2′-bipyridine or bipy
Two nitrogen donor atoms
Ethylene-1,2-bis(diphenylphosphine) or dppe
Two phosphorus donor atoms
bis(dimethylphosphino) ethylene or dmpe