ligand vs polyatomic

[sabrina ghalambor 2J]

i've watched the lecture and a few youtube videos about ligands by now and maybe something just hasn't clicked yet but is there a difference between ligands and polyatomic ions? i understand that the more complex ions are created through reactions but i previously learned about CN- as just a polyatomic ion and not a ligand. are they the same? thank you!

[Gillian Gabrielsen2F]

The difference is a ligand bonds with a central metal ion to form a coordinate complex, while a polyatomic ion is an ionic compound made of multiple atoms. CN- is a polyatomic ion, and due to it's lone pair of electrons on the N and C, it's able to act as a ligand and form a coordinate covalent bond with a Metal ion. Ammonium, NH4+, is a polyatomic ion but it doesn't have a lone pair of electrons to donate so it won't act as a ligand.
A Ligand is a molecule or ion that donates electrons to the central metal to form a coordination complex. A ligand doesn't have to be a polyatomic ion, Water and Ammonia(NH3) are common ligands and are covalent molecules, not ions. for a species to be a ligand, it just needs to be some type of molecule or ion that has lone pair electrons it is able to donate. This means that a ligand can be a singular ion, a covalent molecule, or a polyatomic ion. Hope this helped

[JonathanSung_2G]

Polyatomic ions can act as ligands, and ligands do not necessarily have to be polyatomic ions. Any molecule that is bonded to the center atom, usually a transition metal, acts as a ligand. The coordination sphere consists of the transition metal and all of the ligands that are bonded to it. It just so happens that polyatomic ions can be ligands too. Many different polyatomic ions exist, and the names of these ions dictate how the coordination compound is named as a whole. For instance CN-, or cyanide, would translate to cyano in the naming of the coordination compound.

[sabrina ghalambor 2J]

thank you both!! these were really helpful