Co-ordinate Bond
Chemical compounds are generally formed by a force of attraction between atoms or molecules or ions. This force of attraction is referred to as the chemical bond. The chemical bond keeps the atoms together in the resulting compound. A chemical bond accounts for the stability of a chemical compound. The stronger the bond, the greater is the stability of the compound. It is also true that the compounds are less stable and highly reactive if the chemical bond between the atoms is weak. To attain stability, the atoms either lose or gain energy. Chemical bonds can also be defined as the attractive force that binds two or more atoms together. The different types of chemical bonds are:
Covalent bond
Ionic bond
Hydrogen bond
Polar bond
Introduction:
Coordination compounds are one of the widely used compounds in not only a variety of industrial uses but also in various biological processes. In these types of compounds, there is the presence of a central atom which is then attached to various ligands that are surrounding it. The most common examples of coordination compounds can be seen in Vitamin- B12, hemoglobin, chlorophyll, and pigments. They are also highly used as catalysts in various reactions. These compounds are also sometimes commonly called sandwich compounds as these contain two molecules of an unsaturated cyclic hydrocarbon which leads to more than one hydrogen atom being bonded to either side of a metal atom, hence providing a very stable aromatic system. Students can now also access articles on Co-ordinate Bond – Basics, Characteristics, Example, and FAQs via Vedantu where entire details regarding the same are provided.
Valence Bond Theory:
Valence bond theory is one of the most commonly accepted theories. It was proposed by Linus Pauling and John C. Slater. Here they stated that the bonding is accounted for in terms of hybridized orbitals of the metal ion which is assumed to possess a particular number of vacant orbitals that can easily take in electrons to form a coordinate bond.
What is Coordinate Bond Definition?
A coordinate bond is a special type of covalent bond. It can be defined as an alternate covalent bond in which the electron pair is shared from one atom only. In other words, both the electrons that form the shared pair are from the same atom. The coordinate bonds can also be alternatively referred to as Dative bonds or dipolar bonds. A coordinate bond is also at times referred to as a Coordinate Covalent bond because it is a unique kind of covalent bond. We can visualize coordinate covalent bonds in the reactions that involve two non-metals such as a hydrogen atom. It is also formed in reactions involving metal ions and ligands.
Characteristics of Coordinate Covalent Bond
In coordinate bonding, the donor is the atom that shares a pair of electrons from itself to the other atom.
The acceptor or receptor is the atom that receives the electron pair shared by the donor to attain stability.
The coordinate bond is represented by a small line segment with an arrow pointing to the acceptor indicating the direction of the sharing of the electron pair. The symbol used is ‘→’.
By sharing and receiving the electron pair, the donor and acceptor attain stability.
The coordinate bonding corresponds to the Lewis theory of chemical bonding.
It is easy to write the structures of complex organic molecules with a thorough understanding of the formation of coordinate covalent bonds.
Coordinate Bond Examples
There is a wide range of chemical compounds that we use in our day to day life which are formed by coordinate bonds. A coordinate bond involves the sharing of electrons from one atom only. The other atom just receives the shared electron pair. The direction of sharing is indicated by an arrow. If the coordinate bond is formed between the atoms X and Y, X, being the donor and Y, the receptor, the chemical compound with its bond is represented as:
X → Y
A Few Coordinate Bond Examples are
Formation of Ammonium ion
Formation of Hydronium ion
Formation of Ammonia boron trifluoride
Formation of Ammonium Ion
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The above figure indicates the formation of covalent coordinate bonds during the formation of ammonium ions. The nitrogen atom in Ammonia shares its pair of electrons with the hydrogen ion to make it stable. Hence, the hydrogen atom is the donor in this case. However, the hydrogen ion (H+) ion receives the shared pair of electrons and hence is an acceptor. An arrow pointing towards the Hydrogen atom indicates that the electron pair is shared by nitrogen and accepted by hydrogen.
Formation of Hydronium Ion
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It is clearly indicated in the above representation that one pair of electrons from the oxygen atom of the water molecule is shared with the hydrogen ion to give the hydronium ion (H3O+). Here, the water molecule (H2O) is the donor and the hydrogen ion (H+) is the acceptor.
Formation of Ammonium Boron Trifluoride
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The Ammonium Boron Trifluoride is formed by the sharing of electrons by the Nitrogen atom in Ammonia (NH3) with the Boron atom in Boron Trifluoride (BF3). Here Ammonia is the donor and Boron trifluoride is the acceptor. The arrow towards Boron indicates that the pair of electrons is shared by ammonia with the boron.
Properties of Coordinate Compounds
The compounds that are coordinate bond examples have relatively lower melting and boiling points in comparison to the ionic compounds.
Some coordinate compounds showcase isomerism.
A coordinate bond is a directional bond because the sharing of electrons takes place in a specific direction.
Coordinate bonds are weaker than Ionic bonds.
Fun Facts
A coordinate covalent bond is also called the dative bond or dipolar bond.
Though the electron pair is completely shared by one atom during the formation of a coordinate bond, it is not identical to the ionic bond because neither of the atoms is completely losing or gaining electrons.
FAQs on Co-ordinate Bond
1. How does the formation of Aluminum chloride take place through coordinate bonds?
Aluminum chloride tends to sublimate at about 180 degrees Celsius. Where it turns from a solid phase to a gas phase. If the compound only had ions then it would have a very high melting point and boiling point due to the strong attractions that are present between the positive and negative ions. However, as it sublimes at quite a low temperature it is said to be covalent. Aluminum chloride is electron deficient in nature. It is also seen that when it sublimes it does not stay as a monomer instead it forms a dimer and then sublimes. This bond between the two monomers is said to be coordinated in nature using lone pairs on chlorine atoms. Energy is released when there are two coordinate bonds being formed and hence the dimer tends to be more energetically stable than its monomer structure.
2. Are there coordination compounds present in nature?
Naturally occurring compounds are very important for living organisms. Metalloenzymes are those enzymes that are metal complexes. These also contain coordination bonds. For example, the hydrolytic enzyme is very important in digestion, it consists of zinc ions and is coordinated to various amino acid residues of the protein. The activity of this metal is catalytic in nature. Hemoglobin, which consists of the iron-porphyrin unit, acts as an oxygen carrier in the bodies of living organisms. This hemoglobin is also an important constituent of blood.
3. How are coordination compounds used in industry?
There are several applications of coordination compounds in industry. Prussian blue which is a coordinate compound that acts as a dye for clothes and is also highly used in other dyes and pigments. Phthalocyanine complexes that are closely related to the porphyrins containing copper-phthalocyanine which tend to contain large ring ligands. It is also an important class of dyes for fabrics. The purification of nickel is done by reacting it with carbon monoxide which tends to form tetracarbonylnickel complex which is further distilled and thermally decomposed to deposit pure metal which is also used in various other uses. Gold from its ores can be separated by the usage of aqueous cyanide solutions.
4. What is the history of coordination compounds?
The first known coordination compound was the bright red alizarin dye which was first used in India and was known to the ancient Persians and Egyptians. Apart from this, a sparingly soluble compound was used to refine the element platinum. In the 19th century as and when new compounds were discovered there were more and more theories proposed. The most accepted theory was of Swedish Chemistry Christian Wilhelm Blomstrand which was later on modified and developed by Danish Chemist Sophus Mads Jorgensen. Today he is not only regarded as the father of structural inorganic chemistry but also of coordination chemistry.
5. What does coordination number mean and why is it important to learn about Co-ordinate Bond?
Coordination numbers generally start from 2 and end by 12. Among these 4 which is called tetracoordinate and 6 which is called hexacoordinate are of the most commonly-seen structure. Werner referred to both the ligand and the central atom to which it is attached as the coordination sphere. The coordination number and oxidation numbers are not the same. While coordination means the number of bonds that metal can form, the oxidation number means the charge on the central metal atom that is present. It is hence possible to learn more about Co-ordinate Bond via Vendatu by using the Vedantu NCERT Solutions for Chemistry.
6. How Are Coordinate Covalent Bonds Different from Covalent Bonds?
A covalent bond is formed by mutual sharing of electrons (i.e. both the atoms involved in the bond formation share one electron each) whereas, a coordinate bond is formed by the sharing of electrons by one atom only.
Covalent bonds are formed between two similar or dissimilar atoms. However, coordinate bonds are formed only between unlike atoms.
Covalent bonds may be polar or nonpolar. But, coordinate bonds are always polar because they are formed between two, unlike atoms.
The shared pair of electrons is denoted by a short line (-) in covalent bonds and the same is denoted by an arrowhead indicating the direction of the sharing of the electron pair (→) in coordinate bond.
Covalent compounds are insoluble in water whereas coordinate compounds are sparingly soluble in water.
7. What Are the Differences Between the Coordinate Bond and Ionic Bond?
Ionic bonds are formed by the electrostatic force of attraction between the positively charged cations and the negatively charged anions. However, though the electron pair is shared by one atom only in the case of coordinate bond formation, it does not involve the formation of ions because none of the atoms lose or gain electrons completely.