Homoleptic and Heteroleptic Complex

We must remember that the ligands can be anions, cations, or neutral molecules. And further, we classify Ligands monodentate, bidentate, tridentate and polydentate ligands. In coordination chemistry, the metal is coordinated with ligands in the coordination sphere. The Complexes compounds in which all the ligands are bound to the metal centre which are identical to each other are known as homoleptic complexes and the complexes in which the metal atoms or ions are linked with more than one kind of ligands are known as heteroleptic complexes.

Coordination Compounds 

A coordination complex is a chemical structure in which a central metal atom is surrounded by nonmetal atoms or groups of atoms called ligands that are chemically linked to it. These are examples of coordination compounds:

Types of Coordination Compound on the basis of Type of Ligand

Homoleptic Complex

• Only one type of ligand is attached to the central metal atom, for example

• [Co(en)3]3+
• [Fe(N)6]4-, where CN-= 1 donor

Heteroleptic Complex

• Different types of ligand attached to the central metal atom, for example

• [Pt(NH3)Cl2]
• [CoCl3(NH3)3], where Cl- is one donor, NH3= another donor

What are Homoleptic Complexes?

Homoleptic complexes are chemical compounds with the identical ligands linked to the same central metal atom. Transition metal complexes are the subject of this term in inorganic chemistry.

Dialkyl magnesium complexes, which have two Ether ligands connected to each magnesium centre and exist in a Grignard reagent solution in an Ether, are a common example of such a complex. 

• Trimethylaluminum in an Ether such as THF is another example of a homoleptic compound
• Three methyl groups are linked to a central (+3) positive charge aluminium metal ion in this combination
• Triaryl or trialkyl borane, on the other hand, are homoleptic compounds

Homoleptic: [Sc(H2O)6]Cl3, where Cl is a counterion and six molecules of H2O is a monodentate ligand (neutral).

• [Ni(CN)4]2-, where CN- is the same
• [Hg(Co(SCN)4] – 
• [Fe(CO)5] 
• [Ni(CO)4], where Ni is metal bounded with carbonyl CO, CO is a neutral monodentate ligand
• K3[Fe(C2O4)3] where, C2O42-is oxalate

What are Heteroleptic Complexes?

Chemical compounds with at least one different ligand attached to the metal centre are referred to as heteroleptic complexes. Some ligands, such as DMSO, that are involved in the formation of transition metal complexes, can bind with two or more distinct coordination modes. In this scenario, the metal complex is homoleptic, meaning it contains only one type of ligand with different coordination modes. The cobalt(III) complex, which has four ammonia and two chloride ligands, is a common example of a heteroleptic complex. On the other hand, polynuclear complexes are transition metal complexes with two or more metal centres and associated ligands, which differentiates them from heteroleptic complexes.

• If the ligands connected to the metal centres are different from one another, it is a type of heteroleptic complex

Homoleptic and Heteroleptic Complex: Differences

1. The main distinction between homoleptic and heteroleptic complexes is that homoleptic complexes contain identical ligands connected to a metal atom, whereas heteroleptic complexes have at least one different ligand coupled to the central metal atom.
2. Inorganic chemistry discusses transition metal complexes, and the names homoleptic and heteroleptic complexes are used to describe them. The nature of the ligands connected to the metal centre distinguishes these two types of complexes from one another.

Conclusion

The terms homoleptic and heteroleptic complexes are used to describe transition metal complexes in inorganic chemistry. The nature of the ligands attached to the metal centre distinguishes these two types of complexes from one another. The primary difference between homoleptic and heteroleptic complexes is that homoleptic complexes contain identical ligands coupled to a metal centre, whereas heteroleptic complexes have at least one different ligand attached to the complex’s metal centre.