Question
Explain with two examples each of the following: Coordination entity, ligand coordination number, coordination polyhedron, homoleptic and heteroleptic.
✓
Answer
Coordination entity: This entity usually constitutes a central metal atom or ion, to which are attached a fixed number of other atoms or ions or groups by coordinate bonds. Examples are $\ce{[Ni(CO)_4], [COC]_3(NH_3)_3],}$ etc.
Ligands: It is an ion having at least one lone pair of electrons and capable of forming a coordinate bond with central atom/ion in the coordination entity.
Examples are: $\ce{Cl^-, (OH)^-, (CN)^-}$ etc.
Coordinate number: The total number of coordinate bonds with which central atom/ion is linked to ligands in the coordination entity is called coordination number of central atom / ion.
Coordination polyhedron: The spatial arrangement of the ligands which are directly attached to the central atom / ion defines a coordination polyhedron about the central atom.
Examples are: $\ce{[Co(NHM_3)_6]^{3+}}$ is octahedral,
$\ce{[Ni(CO)_4]}$ is tetrahedral.
Homoleptic and hedroleptic: Complexes in which a metal is bound to only one kind of donor groups are known as homoleptic.
Example $\ce{[CO(NH_3)_6]^{3+}}$
Complex in which a metal is bound to more than one kind of donor groups are called hetroleptic. Example: $\ce{[Co(NH_3)_4Cl_2]^+}$
Ligands: It is an ion having at least one lone pair of electrons and capable of forming a coordinate bond with central atom/ion in the coordination entity.
Examples are: $\ce{Cl^-, (OH)^-, (CN)^-}$ etc.
Coordinate number: The total number of coordinate bonds with which central atom/ion is linked to ligands in the coordination entity is called coordination number of central atom / ion.
Coordination polyhedron: The spatial arrangement of the ligands which are directly attached to the central atom / ion defines a coordination polyhedron about the central atom.
Examples are: $\ce{[Co(NHM_3)_6]^{3+}}$ is octahedral,
$\ce{[Ni(CO)_4]}$ is tetrahedral.
Homoleptic and hedroleptic: Complexes in which a metal is bound to only one kind of donor groups are known as homoleptic.
Example $\ce{[CO(NH_3)_6]^{3+}}$
Complex in which a metal is bound to more than one kind of donor groups are called hetroleptic. Example: $\ce{[Co(NH_3)_4Cl_2]^+}$
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