Co-ordinate Bond

A Co-ordinate bond, also known as a dative covalent bond, is a type of covalent bond formed between two atoms where both electrons in the bond are provided by one atom. Unlike a typical covalent bond, where each participating atom contributes one electron to form a shared pair, in a coordinate bond, both electrons come from the same atom.

1.0Introduction to Coordinate Bond

Coordinate bonds are commonly seen in coordination complexes in chemistry, where a central metal ion or atom forms bonds with surrounding ligands. These ligands often donate electron pairs to the metal center through coordinate bonds.

Understanding the definition of co-ordinate bond, lets see its formation.

This type of bond is typically formed when one atom donates a lone pair of electrons to another atom that has an electron deficiency. The atom donating the electron pair is called the donor, and the atom receiving the pair is called the acceptor.

For examples of co-ordinate bond, let's check the formation of the ammonium ion , a coordinate bond is formed between the lone pair of electrons on a nitrogen atom in ammonia 

The bond between the nitrogen and the hydrogen in the ammonium ion is a coordinate bond, where the lone pair of electrons on the nitrogen atom is shared with the hydrogen ion.

Necessary conditions for the formation of a coordinate bond include:

(a) The donor atom should have a complete octet and at least one lone pair of electrons.

(b) The acceptor atom should have a vacant orbital to accommodate the lone pair.

In essence, a coordinate bond forms when one atom donates a lone pair of electrons to another atom with an empty orbital. This results in the sharing of electrons and the formation of a coordinate covalent bond.

Other examples of co-ordinate bond-

Note- Compounds in which Co-ordinate bonds are present, are as follows -     

NH₄Cl, Na₃PO₄, KNO₃, etc.

2.0Characteristics of Coordinate Covalent Bond

1. Electron Donor-Acceptor Relationship: One atom provides both electrons for the bond, while the other doesn't contribute electrons, establishing a donor-acceptor relationship.

2. Formation from Lewis Bases and Acids: Arises between a Lewis base (donor) with a lone pair and a Lewis acid (acceptor) with an empty orbital, facilitating the sharing of electrons.

3. Directionality: Represented by an arrow from the donor atom to the acceptor atom, indicating the movement of the electron pair.

4. Strength and Length: Exhibits bond strength and a specific bond length like regular covalent bonds, determined by the atoms involved and their electronic configurations.

3.0Properties of Coordinate Bond

(a)  Covalent bond in which the shared e^– pair comes from one atom is called coordinate bond.

(b) Atoms which provide electron pairs for sharing are called donor (Lewis base).

(c)  Another atom which accepts electron pairs is called an acceptor (Lewis acid). That is why it is called donor-acceptor or dative bond.

 To enhance our comprehension Let's explore a few co ordinate bond examples.

4.0Examples of Co-ordinate Bond 

Co-ordinate bond examples involve Formation of Ammonia Boron Trifluoride and Hydronium ion.

Another important example is Formation of Hydronium ion-

5.0Conditions for the Formation of Coordinate Bond

Necessary conditions for the formation of coordinate bond are -

(a)  Octet of donor atoms should be complete and should have at least one lone pair of       electrons.

(b)  Acceptor atoms should have a vacant orbital to accommodate L.P.