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Coordination Compounds
What is spectrochemical series? Explain the difference between a weak field ligand and a strong field ligand.
Spectro-chemical series is a series in which the ligands have been arranged in order of increasing magnitude of splitting they produce. The order is
I– < Br– < SCN– < Cl– < S2– < F – < OH– < C2O42– < H2O < NCS–< edta4– < NH3 < en < CN– < CO
The ligand present on the R.H.S of the series are strong field ligand while L.H.S are weak field ligand. Also, strong field ligand cause higher splitting in the d- orbitals than weak field ligand .
Weak field ligand | Strong field ligand |
1.They are formed when the crystal field stabilisation energy (Δ0) in octahedral complexes is less than the energy required for an electron pairing in a single orbital (p).
| 1. They are formed when the crystal field stabilisation energy (Δ0) is greater than the p.
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2. They are also called high spin complexes.
| 2. They are called low spin complexes.
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3. They are mostly paramagnetic in nature complex.
| 3. They are mostly diamagnetic or less paramagnetic than weak field.
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Indicate the type of isomerism exhibited by the following complexes and draw structures for these isomers:
(i) K[Cr(H2O)2(C2O4)2], (ii) [Co(en)3Cl3,
(iii) [Co(NH3)5(NO2)]|NO3]2, (iv) [Pt(NH3)(H2O)Cl2]
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