Classify weak and strong ligands out of:
(a) OH−
(b) F−
(c) I−
(d) NH3
(e) CH3COO−
(f) en
(g) CN−
(h) Cl−
(i) H2O
F−,I−,Cl− and H2O are weak ligands, other are strong ligands.
If true enter 1, else enter 0.
Hint: To answer this question, it’s important to remember the concept of the Spectrochemical series. Strong ligands are able to donate their electron pairs to the acceptor more effectively.
Complete step by step answer:
– The spectrochemical series is essentially a ranking of ligands based on their strength (ability to donate electron pairs) and also lists metal ions according to their oxidation states, group, and identity.
– In crystal field theory, ligands influence the energy gap between d orbitals, known as the ligand-field splitting parameter or crystal-field splitting parameter, which is often reflected in the color variations of similar metal-ligand complexes.
Weak ligands:
I−,Br−,SCN−,N3−,F−,H2NCONH2,ox2−,O2−,H2O,NCS−,py,NH3,en, bpy
Strong ligands:
NO2−,CH3−,C6H5−,CN−,CO
- Let’s explore the fundamental idea behind crystal field theory.
Simply put, this theory explains how orbital degeneracy is broken in transition metal complexes due to the presence of ligands. It also describes the strength of metal-ligand bonds, as the stability of the system changes depending on the strength of these bonds.
Now, let’s examine the distinction between weak ligands and strong ligands.
|
Weak ligand |
Strong field ligand |
| A weak ligand, also called a weak field ligand, produces a lower crystal field splitting.Complexes formed with weak ligands are typically high-spin complexes and are usually paramagnetic. | A strong ligand, or strong field ligand, results in higher crystal field splitting.Complexes formed with strong ligands are known as low-spin complexes and are generally diamagnetic or less paramagnetic than those with weak ligands. |
F−,I−,Cl−,H2O are weak ligands, others are strong ligands. This statement is false as en is also a weak ligand. en stands for ethylene diamine ligand. Therefore, enter 0.
Note: You should know that sometimes there are exceptional cases where weak field ligand acts as strong field ligand. For example; [PtCl4]2− and CoF63−.
