Name: Nomenclature of Coordination Compounds - I
Uploaded: 2019-07-19
Duration: 7 min 4 s
Description: All the chemical compounds are assigned a name, which is done according to a specific rule. How are coordination compounds named? Let’s watch the video to fi...

Question

Explain with two examples each of the following: coordination entity, ligand, coordination number, coordination polyhedron, homoleptic and heteroleptic.

Accepted Answer

(i) Coordination entity:
It is the radical or species that have a positive or negative charge. The central atom or ion is surrounded by a number of neutral molecules or negative ions (called ligands). For example:
${[N i {(N H_{3})}_{6}]}^{2 +}, {[F e {(C N)}_{6}]}^{4 +} =$ cationic complex
${[P t C l_{4}]}^{2 -}, {[A g {(C N)}_{2}]}^{-} =$ anionic complex
$[N i {(C O)}_{4}], [C o {(N H_{3})}_{4} C l_{2}] =$ neutral complex.

(ii) Ligands
The neutral molecules or negatively charged ions that surround the metal atom in a coordination entity or a coordinate complex are known as ligands. They donate a lone pair of electrons. For example, $\ddot{N} H_{3}, H_{2} \ddot{O}, {Cl}^{-} .$

(iii) Coordination number:
The total number of lone pairs donated by ligands (either neutral molecules or negative ions) attached to the central metal atom in the coordination sphere is called the coordination number of the central metal atom.
For example:
(a) $K_{2} [P t C l_{6}],$ six chloride ions attached to $P t$ in the coordinate sphere. So the coordination number of $P t$ is $6 .$
(b) $[N i {(N H_{3})}_{4}] C l_{2},$ the coordination number of the central atom $(N i)$ is $4 .$

(iv) Coordination polyhedron:
The spatial arrangement of the ligands attached to the central metal ion directly in the coordination sphere.
For example:
(a)

(b) Tetrahedral

(v) Homoleptic complexes:
The complexes in which the metal ion bonded to only one kind of donor group. For e.g.: ${[C o {(N H_{3})}_{6}]}^{3 +}, {[P t C l_{4}]}^{2 -}$ , etc.
(vi) Heteroleptic complexes:
The complexes in which the central metal ion is bound to more than one type of donor group.
For e.g.: ${[C o {(N H_{3})}_{4} C l_{2}]}^{+}, {[C o {(N H_{3})}_{5} C l]}^{2 +}$ .

Explain with two examples each of the following: coordination entity, ligand, coordination number, coordination polyhedron, homoleptic and heteroleptic.

Important Questions on Coordination Compounds

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