Difference Between Coordination Entity and Coordination Sphere

Key Difference – Coordination Entity vs Coordination Sphere
 

The key difference between coordination entity and coordination sphere is that the coordination entity is the collection of a central atom and the ligands surrounding the atom whereas coordination sphere is coordination entity given with electrical charge of the coordination compound.

A coordination compound is a complex chemical compound composed of a central atom (usually a meta-atom or a metal ion) surrounded by molecules or ions known as ligands. These ligands are bound to the central metal atom via coordinate covalent bonds. These bonds are formed when electron-rich molecules or ions donate their lone electron pairs to a metal atom (or ion).

CONTENTS

1. Overview and Key Difference
2. What is Coordination Entity
3. What is Coordination Sphere
4. Side by Side Comparison – Coordination Entity vs Coordination Sphere in Tabular Form
5. Summary

What is Coordination Entity?

Coordination entity is the collection of components of a coordination compound including the central atom and the ligands surrounding this central atom. The ligands are bonded to the central atom via coordinate covalent bonds. A coordinate covalent bond is formed when an electron-rich molecule or ion donates its lone electron pairs to an electron-deficient atom.

The central atom is most of the times a metal atom in d-block. That is because d-block elements have many empty d orbitals (enough space for incoming lone electron pairs). For example, the coordination entity of [CoCl₂(NH₃)₄]⁺ is CoCl₂(NH₃)₄. The central metal atom is cobalt (Co).

What is Coordination Sphere?

Coordination sphere is the collection of components of a coordination compound which includes the central atom and the ligands surrounding this central atom given along with the net electrical charge of the compound. The central metal atom is most of the times a positively charged component (a cation). Some ligands are neutrally charged (and contain lone electron pairs that can be donated) whereas other ligands are negatively charged (anions). Therefore, the net charge of the coordination compound is determined by both the central metal ion and the charge of ligands.

Figure 01: First Coordination Sphere of Trans-dichlorotetraamminecobalt(III)

The coordination spheres can be found in two types as first coordination sphere and the second coordination sphere. The first coordination sphere includes the ligands that are directly attached to the metal ion whereas second coordination sphere includes the indirectly bonded molecules and ions as well. For example, the first coordination sphere of [CoCl₂(NH₃)₄]Cl is of [CoCl₂(NH₃)₄]⁺ whereas the second coordination sphere is Cl^– ion.

What is the Difference Between Coordination Entity and Coordination Sphere?

Summary – Coordination Entity vs Coordination Sphere

The coordination compounds contain a central metal atom or ion surrounded by molecules or ions known as ligands. These ligands are electron-rich components that can donate electron pairs to the metal atom. the coordination entity and coordination sphere are two terms that are discussed regarding coordination compounds. The difference between coordination entity and coordination sphere is that the coordination entity is the collection of a central atom and the ligands surrounding this atom whereas coordination sphere is coordination entity given with electrical charge of the coordination compound.

Reference:

1. “Coordination Sphere.” Wikipedia, Wikimedia Foundation, 17 Feb. 2018. Available here  
2. Libretexts. “Introduction to Coordination Chemistry.” Chemistry LibreTexts, Libretexts, 20 Apr. 2017. Available here  

Image Courtesy:

1.’Trans-dichlorotetraamminecobalt(III)’By Benjah-bmm27 – Own work, (Public Domain) via Commons Wikimedia  

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