Coordination Compound poses 2-3 questions every year in JEE Main. An important aspect of inorganic chemistry comprising questions from theory as well as numerals. Class 12^th NCERT is best advised to cover up the chapter along with previous year question paper.

• The compounds that retain their identities even after getting dissolved in water or in any other solvent; there properties are totally different from those of the individual components, are being referred to as Coordination Compounds. Read JEE Main Chemistry Preparation 
• Some of the examples of coordination compounds include Ni(NH3)6]Cl2; Co(NH3)6]Cl3, etc.
• Nomenclature should be practiced well along with clarity on Valence Bond Theory.
• Learn spectrochemical series well, it is essential to know strong and weak ligands at your fingertips.
• Not much time is needed on colours and wavelengths or use of coordination compounds, though should not be left.

JEE Main 2020 is scheduled to be conducted from July 18 to 23, 2020. Beneath we are discussing Chemistry Coordination which is an important part in Inorganic Chemistry and holds significant weightage.

Quick Links:

• JEE Main Admit Card
• JEE Main Question Papers
• JEE Main Exam Dates
• JEE Main Syllabus

Ligands and their Types

Chelating Ligands

Multidentate ligand that combine together with a metal ion via more than one site are referred as chelating ligand. A few examples of chelating ligands include Ethylenediamine. These ligands produce a ring like structure known as chelate which improves the stability of complex.

Must Read:

• JEE Main Study Notes for Equilibrium
• JEE Main Study Notes for s block Elements
• JEE Main Study Notes for States of Matter

Bonding in Coordination Compounds

What is Werner’s Theory?

• According to the Werner’s Theory, the metals possess two types of valencies including primary (ionizable) valency and secondary (nonionizable) valency.
• Secondary valency of a metal is equal to the total number of ligands fixed to it, coordination number.
• Primary valencies are satisfied by the negative ions; however, secondary valencies gets satisfied by positive, neutral, or negative ions

Secondary valencies have constant orientations around the metal in space.

• [Co(NH3)6]Cl3
• Primary Valencies = 3 Cl-
• Secondary Valencies = 6 NH3
• Coordination Sphere = [Co(NH3)6]3-

Valence Bond Theory (VBT)

Valence Bond Theory was initiated by L. Pauling in early 1930s. As per this theory, when a complex is formed, the metal ion/atom provides empty orbitals to the ligands located at the surrounding places. Coordination number shows the number of such empty orbitals, i.e., number of empty orbitals will be equal to the coordination number. These empty orbitals hybridised before taking part in the bonding and the nature of hybridisation is based on the nature of metal and on the approaching ligand as well.

Nomenclature of Coordination Compounds

Nomenclature of coordination compounds adopts a unique set of different rules discussed below:

• Name the cation, then anion
• Non ionic compounds are given one-word name
• Name ligands

1. Ligands are named first while the central atom are the last
2. Ligands are considered in the alphabetical order
3. Neutral ligands are named the same as the molecule (except aqua and ammine)
4. Anionic ligands are named by adding - O to the stem of the name (chloride becomes chloro)
5. The ligand name is preceded by a numerical prefix to indicate how many are present - di, tri, tetra, penta, hexa

In a neutral or cationic complex, the name of the central metal atom is followed by its oxidation number in Roman numerals in parentheses

In anionic complex, the suffix- ate is added to the name of central metal, followed by its oxidation number in Roman numerals in parentheses

In case of bridging ligand the word m (mu) is written before the name of ligand

Must Read:

• JEE Main Mathematics Preparation Tips
• JEE Main Physics Preparation Tips

Quick Tips on Coordination Compounds

Q1. What is Complex Chemistry?

The branch of chemistry that includes the study of the Coordination Compounds or Complex Compounds and their uses is known as Complex Chemistry.

Q2. Why the transition metal compounds forms complexes?

The transition metals are different in their tendency to produce coordination complexes. The tendency of cations of transition elements to produce complexes is mainly due to the following factors:

• These ions are smaller in size and thus have high positive charge density. This improves acceptance of lone pair of electrons from other molecules.
• They have vacant orbitals and these orbitals have the appropriate type of energy to accept lone pair of electrons.

Q3. What is a Coordinate Bond?

When both the electrons shared among the atoms are contributed by one atom only, then this kind of relation is referred to as Coordination Bond. It is also called Dative Bond. The coordinate bond is established between two atoms out of which one has a complete octet with minimum one pair of unshared electrons while the other is short of two electrons. The Coordinate Bond is shown by (a) sign.

Example: An example of Coordinate bond includes the formation of hydronium ion from water molecules. In this case, oxygen atom in water molecule is the donor while hydrogen ion will be the acceptor.

Read How to Effectively Prepare for the Coming JEE Main Session from Home?

Solved Example on Coordination Compound

Q1. What is Mohr’s salt?

• Double salt
• Coordination compound
• Both
• None

The correct answer is coordination compound

Q2. Secondary valancy of [Cu(NH3)4]2+ will be

• 1
• 2
• 3
• 4

The correct answer is 4

Q3. Total number of legand in [Cr(H2O)4Cl2]+ will be

• 6
• 4
• 2
• 1

The correct answer is 6

Q4. EDTA Means

• Unidentate ligands
• Bidentate ligands
• Ridentate ligands
• exadentate ligands

The correct answer is exadentate ligands

Q5. Carbonate ion(CO32–) acts as a

• Tridentate ligand
• Bidentate ligand
• Monodentate ligand
• Tetradentate ligand

The correct answer is Bidentate ligand

Q6. Which of the following co-ordination number is new for Co3+?

• 5
• 4
• 6
• zero

Zero is the correct answer

Also Check:

• JEE Main Study Notes for Surface Chemistry
• JEE Main Study Notes for States of Matter

Important Terms to Solve Coordinate Compound Questions

Complexion - An electrically charged ion that includes a central metal atom/ion surrounded by a group of ions or neutral atom is termed as complex ion.

• Cationic complex entity - It is the complexion that holds carries positive charge. e.g., [Pt(NH3)4]2+
• (ii) Anionic complex entity - It is the complexion that holds negative charge. e.g., [Fe(CN)6]4-

Central Ion and Ligand- The cation to which one or more neutral molecules are grouped together is known as the Central Ion and the attached molecules are referred to as Ligands. For instance, in [Ni(NH3)6]+2 Ni+2 is the central ion surrounded by ammonia ligands.

Coordinate Number: The total ligands that are attached to a central metal ion/atom are known as the Coordinate Number of that particular ion.

Coordinate Sphere: The central metal ion along with molecules or ion coordinated to it means Coordinate Sphere. Coordinate sphere explained by written inside a “[ ]” square bracket.

Complex- A central metal atom /ion that is surrounded by a set of ligands.

Ligand- An ion or a molecule that has an independent existence and is able to donate a pair of electrons. The ligand can be negative ion, neutral molecule or positive cation (though rare in nature).

Coordination Compound

• A neutral complex or ionic compound where at least one of the ions is a complex formed between a lewis acid (-acceptor) and lewis base.
• Ni = lewis acid centre, NH3 = Lewis base
• Complexion is always written in square brackets

Coordination Number

Total ligand donor atoms present in a coordination compound (or complex) or a number of electron pairs that arise from ligand donor atoms to which the metal is directly bonded are known as coordination numbers. These number varies from 1 to 12 (> 12 for some f- block element.

Complex- A central metal atom /ion that is surrounded by a set of ligands is referred to as Complex.

Ligand- An ion or a molecule that has an independent existence and can donate a pair of electrons. It can be negative ion, neutral molecule or positive cation (though rare in nature).

Chelate Complex

Chelate complex is obtained when a bi or polydentate ligand uses two or more donor atoms to bind to one metal atom. Most of the common elements that act as donor atoms include N, P, O, S halides and C ( in organic metallic compounds)

Bridging Ligands- These bridging ligands are helpful to bind to more than one metal atom.

Homoleptic ligand- These metals bound to only one type of donor group

Heteroleptic Ligand- The metal bound to more than one type donor group.

Coordination sphere- The combination of central metal atom and ligands written in “square brackets” is called the coordination sphere.

Practice with JEE Main Question Paper

Uses of Coordination Compounds

These compounds are mostly used now days. Some of their applications are mentioned below:

• In the extraction process of gold and silver
• It is used as a catalyst in several industrial processes.
• Example: Nickel, Copper can be extracted with the help of hydrometallurgical process involving coordination compounds.
• It is used in hardness of water.
• Example: EDTA (Ethylenediaminetetraacetate) is used in the estimation of Ca+2 and Mg+2 in hard water.
• Cyanide complexes are used in electroplating.

JEE Main Chemistry Preparation Tips

• Chemistry is the most scoring subject in the IIT JEE exam as it mostly includes solving the questions using different formulas and equations. The questions asked in Chemistry are more theoretical instead of calculative, which makes it easier for the test-takers to solve them.
• Unlike the other subjects, IIT JEE Chemistry is less about conceptual applications but more about systematic planning. To get a higher score in this section, the aspirants need to be well aware of the latest formulas, reactions, chemical equations, theories, etc. as plays a vital role in exam preparations.
• A lot of direct and indirect questions are asked in the test.
• The key to solving chemistry problems is to have a broader and clear understanding of the fundamental concepts. Students with a solid conceptual foundation will be able to crack the IIT JEE Chemistry problems easily.
• Remember all the important theories and formulas that will help the JEE aspirants in solving different problems. You can pen down important formulas and keep them handy.
• The students can consider the best IIT JEE Chemistry study material so that they can study basic concepts covered in Organic, Inorganic, and Physical Chemistry. By analysing important topics and their weightage, students can plan their studies accordingly.

All the IIT aspirants must start revising these notes so that they can ace the exam which is scheduled to be conducted in July 2020.

Weightage of Inorganic Chemistry

Chemistry is one of the most essential and scoring subjects in the IIT JEE exams. The questions asked in the chemistry section are mostly straight forward but getting a higher score in this section is quite a challenging task. All the sections have their own weightage and it is important to prepare for all of them.

The Elements of the periodic table and Chemical Bonding are the most important topics for JEE Main 2020. These two topics should be on your tips. They are important for building a solid foundation for Inorganic chemistry. Questions asked from Coordination Compounds are based on the following topics:

• Ligands
• What is Werner’s Theory
• Complex Chemistry?
• Transition metal compounds

Besides the above-mentioned topics, many others topics are important in Coordination Compounds that help the students to prepare effectively and score better in IIT JEE Chemistry past. Most of the questions are asked from inorganic chemistry section. However, other sections are also important and the test-takers much have a good knowledge of all the parts.