Bonding In Coordination Compounds
Chapter Name : Coordination Compounds |
Sub Topic Code : 102_12_09_05_03 |
Topic Name : Bonding In Coordination Compounds |
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Sub Topic Name : Limitations Of Valence Bond Theory |
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Introduction
Coordination complex or metal complex, consists of an atom or ion (usually metallic), and a surrounding array of bound molecules or anions, that are in turn known as ligands or complexing agents.
Pre-Requisites:
Coordination Compounds
Activity:
Nickel tetracarbonyl.
Real Life Question:
What is Valence bond (VB) theory?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Valence bond (VB) theory | Valence bond (VB) theory is one of two basic theories, along with molecular orbital (MO) theory, that were developed to use the methods of quantum mechanics to explain chemical bonding. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Ligand field theory | Ligand field theory (LFT) describes the bonding, orbital arrangement, and other characteristics of coordination complexes. |
Real life uses :
Study of organometals.
Places to visit :
Pharmacy.
Practical examples around us
| Examples | Explainations |
|---|---|
| Nickel tetracarbonyl | It is an intermediate in the Mond process for the purification of nickel and a reagent in organometallic chemistry. |
What you learn in Theory:
The valence bond theory was fairly successful in explaining qualitatively the geometry and magnetic behavior of the complexes. But, it could not explain the following : (i) The origin of their absorption spectra could not be explained. (ii) Why did different complexes of the same metal show different colours? (iii) Relative stabilities of different complexes could not be explained. (iv) Why should certain ligands form high spin, while others low spin complexes? (v) it assumes all bonds are localized bonds . As we will see, this is not a valid assumption.
What you learn in Practice:
A covalent bond is formed between the two atoms by the overlap of half-filled valence atomic orbitals of each atom containing one unpaired electron.