MediumChemistryHigh School (11–12)Coordination Compounds › Werner's Theory, Ligands and NomenclatureConceptualNumericalA-LevelBoard ExamIB
The glycinate ion, H₂N-CH₂-COO⁻, bonds to a metal ion through its nitrogen atom and one oxygen atom…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The glycinate ion, , bonds to a metal ion through its nitrogen atom and one oxygen atom of the carboxylate group. Say what kind of ligand it is. How many donor atoms does it use? How many atoms are in the ring that it closes with the metal ion?
Need a reminder? The key ideaShow
The coordination number is the number of donor atoms bonded to the metal, not the number of ligands. The charge on a complex is , where is the oxidation state of the metal. A ligand with two or more donor atoms is chelating, and EDTA has six.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The donor atoms. Nitrogen and one oxygen: 2 donor atoms. They both bond at the same time, so the ion is a bidentate chelating ligand.
Step 2. The ring. Going round: metal, N, the carbon of , the carbon of , O, and back to the metal. That is 5 atoms, so the ring is five-membered.
Answer: it is a bidentate chelating ligand with 2 donor atoms, and it closes a ring of 5 atoms.
What if? The ion could never close a ring with a single donor atom. A monodentate ligand cannot chelate.
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