Limitations of valence bond theory

 Limitations of valence bond theory  

The valence bond theory was sadly successful in explaining qualitative only the geometry and magnetic properties of complexes however it has a number of limitations.  

these are as follow- 

• i) It involves a no. of assumptions such as electronic configuration, hybridization, overlapping etc. 

• ii) it does not give quality quantitative interpretation of magnetic data it does not explain the colour exhibited by coordination compound in does not give a quantitatively interpretation of the thermodynamic of kinetic stability is of coordination compound in does not make exact prediction regarding the tetrahedral and Square planar structure SOF 

• iii) it does not explain the colour exhibited by coordination compound  

• iv) it does not give a quantitatively interpretation of the thermodynamic of kinetic stability is of coordination compounds 

• V) it does not make exact prediction regarding the tetrahedral and Square planar structures of 4-coordinate complexes  

• Vi). It does not distinguish between weak and strong ligands. 

 Differences between inner orbital octahedral complexes and Outer orbital octahedral complexes 

Inner orbital octahedral complexes  or low spin complexes	Outer orbital octahedral complexes or high spin complexes
a. formed by hybridization of d2sp3 hybridisation. These are formed in the presence of strong ligands.   b. These complexes generally possess a smaller number of unpaired electrons i.e., they show either low or no magnetic moment.   c. These are less reactive i.e., more stable. Substitution reactions are difficult to occur.	a. formed by hybridisation of sp3d2 hybridisation. These are formed in presence of weak ligands.   b. These complexes generally possess greater number of unpaired electrons i.e., they show high magnetic moment.    c. These are reactive i.e., less stable. Substitution reactions are easy to occur.

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