5 Important Complex Ion Examples You Need To Know


Complex ion is an ion that contains a central metal ion bonded to one or more ligands through a dative covalent bond. Ligands are attached to a central metal ion through a dative covalent bond. Some of the example for the ligands are water, ammonia, cyanide ion, chloride ion, etc. Here are the complex ion examples.

  1. [Co(NH3)6]3+
  2. [Ni(CN4)]2-
  3. [CoF6]3-
  4. [Fe(H2O)6]3+
  5. [Cu(NH3)4(H2O)2]2+
  6. Pt(NH3)2Cl2

1.[Co(NH3)6]3+

hexamminecobalt (ΙΙΙ)

IUPAC Nomenclature of [Co(NH3)6]3+ is hexamminecobalt (ΙΙΙ) ion. Here, cobalt is the central metal whose oxidation state is +3 and bonded to the six ammonia ligands. The electronic configuration of cobalt and cobalt in +3 state is

Co → [Ar]3d74s2

Co+3 → [Ar]3d64s0

Co3+ ion has four unpaired electron in 3d-subshell. Since NH3 acts as a strong ligand causes pairing by leaving two d-orbitals empty.

In order to form six covalent bonds with the six ligand, six atomic orbital should be hybridized. In order to make bond with the six ammonia ligand, two 3d electron shell, one 4s and three 4p orbital undergoes hybridization to form d2sp3 hybridization.

The complex formed from this metal atoms are inner orbital complex because a central metal atom undergoes hybridization of atomic orbital including 3d orbital which is located inside the 4s and 4p orbitals.

The complex ion [Co(NH3)6]3+ is formed by d2sp3 hybridization and it possess octahedral geometry. Due to the absence of unpaired electrons, it is diamagnetic in nature. Hexamminecobalt (ΙΙΙ) ion is used in DNA condensation studies and it activate some of enzymes that requires magnesium. 

2. [Ni(CN4)]2-

IUPAC nomenclature of [Ni(CN4)]2- is tetracyanonickelate (ΙΙ) ion. Here, Nickel is the central metal whose oxidation state is +2. The electronic configuration of nickel and nickel in +2 state

Ni → (Ar)3d84s2

Ni2+ → (Ar)3d84s0

Ni2+ ion has two unpaired electron in 3d-subshell. Since CNacts as a strong field ligand causes pairing by leaving one d-orbitals empty. In order to form four covalent bonds with the four ligand, four atomic orbital should be hybridized. To make bonds with the CN ligand, empty orbitals of one 3d, one 4s and two 4p orbital undergoes dsp2 hybridization.

The complex formed from this metal atoms are inner orbital complex because a central metal atom undergoes hybridization of atomic orbital including 3d orbital which is located inside the 4s and 4p orbitals. The complex ion [Ni(CN4)]2- is formed by dsp2 hybridization and it possess square planar geometry. Due to the absence of unpaired electrons, it is diamagnetic in nature.

3. [CoF6]3-

hexafluorocobaltate (ΙΙΙ)

IUPAC nomenclature of [CoF6]3-is hexafluorocobaltate (ΙΙΙ) ion. Here, cobalt is the central metal whose oxidation state is +3. The electronic configuration of cobalt and cobalt in +3 state is

Co → [Ar]3d74s2

Co+3 → [Ar]3d64s0

Co3+ ion has four unpaired electron in 3d-subshell. Since fluorine ion acts as a weak ligand it cannot causes pairing of the 3d-orbitals. In order to form six covalent bonds with the six ligand, six atomic orbital should be hybridized. Therefore one of the 4s orbitals, three 4p orbital and two 4d orbital are involved in hybridization Hence it is sp3d2 hybridization.

In the hybridization s, p and d orbital are in nd that is 4d electron shell which is located outside the s and p orbitals. The complexes formed from this metal atoms are outer orbital complexes. The complex ion [CoF6]3- is formed by sp3d2 hybridization and it possess octahedral geometry. Due to the presence of unpaired electrons, it is paramagnetic in nature.

4. [Fe(H2O)6]3+

hexaaquairon (ΙΙΙ) ion

IUPAC nomenclature of [Fe(H2O)6]3+ is hexaaquairon (ΙΙΙ) ion. Here, iron is the central metal whose oxidation state is +3. The electronic configuration of iron and iron in +3 state is

Fe   →  (Ar)3d64s2

Fe3+ → (Ar)3d54s0

Fe3+ ion has five unpaired electron in 3d-subshell. Since water acts as a weak field ligand it cannot causes pairing of 3d-orbitals. In order to form six covalent bonds with the six ligand, six atomic orbital should be hybridized. Therefore one of the 4s orbitals, three 4p orbital and two 4d orbital are involved in hybridization Hence it is sp3d2 hybridization.

The complex formed from this metal atoms are outer orbital complex because a central metal atom undergoes hybridization of atomic orbital including 4d orbital which is located outside the 4s and 4p orbitals. The complex ion [Fe(H2O)6]3+ is formed by sp3d2 hybridization and it possess octahedral geometry. Magnetic property of this complex is it paramagnetic in nature because of the presence of unpaired electrons.

5.[Cu(NH3)4(H2O)2]2+

IUPAC Nomenclature of [Cu(NH3)4(H2O)2]2+ is tetraamminodiaquacopper (ΙΙ) ion. Here, two types of ligands are present they are ammonia and water which are neutral ligands which does not have any charge.

It shows two geometrical isomerism of cis and trans. If two water molecule are adjacent to each other than it is cis-isomer whereas, if two water molecule are opposite to each other than it is trans-isomer. The oxidation number of the copper atom in the [Cu(NH3)4(H2O)2]2+ is +2 state. Geometry of this complex is octahedral and it appear in deep blue-violet color.

6. Pt(NH3)2Cl2

Structure of diamminedichloridoplatinum (ΙΙ) ion. image credit: Wikimedia commons

IUPAC nomenclature of Pt(NH3)2Cl2 is diamminedichloridoplatinum (ΙΙ). The oxidation state of platinum is +2. Two types of the ligands are present they are ammonia and chlorine groups around a central metal atom platinum are all on the same plane therefore geometry of this complex is square planar.

It shows two geometrical isomerism of cis and trans. If two chlorine groups are adjacent to each other than it is cisplatin whereas, if two chlorine groups are opposite to each other than it is transplatin.

Cisplatin has a platinum as the central metal and it exhibits cis-isomers. It is a platinum complex ion used as anticancer to cure cancer like lungs, bladder, cervical and ovarian.

Summary:

Complex ion is an ion that contains one or more ligands that are attached to a central metal atom. IUPAC nomenclature, hybridization, geometry and magnetic property of different type of complexes are discussed. Here, it summarizes use of cisplatin and their geometrical isomerism with structure.

Supriya Upadhya

I am Post Graduate in Organic chemistry with good understanding of Chemistry concepts and worked as Junior research fellow in synthesis of anti cancer agent. Also worked on Anti-Microbial Polymer synthesis as part of Post graduate thesis.

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