9.3 Explain with two examples each of the following: coordination entity, ligand, coordination number, coordination polyhedron, homoleptic and heteroleptic.
(i) Coordination entity:- It is an electrically charged species carrying either a positive charge or a negative charge. In a coordination entity, the central atom or ion is surrounded by some number of neutral molecules or negative ions ( called ligands) accordingly.
(ii) Ligand:- Ligands are the neutral molecules or negatively charged ions that surround the metal atom in a coordination entity according to the holding capacity of central metal ion are known as ligands. NH3 and H2O are two neutral ligands.
(iii) Coordination number:- The total number of metals that surrounds the central metal ion is known as coordination number.
For e.g,(a) In case of six chlorine atoms are attached to Pt, thus the coordination number of the given compound is 6.
(b) In case of the central metal ion Ni is surrounded by 4 atoms of ligand so its coordination number is 4.
(iv) Coordination polyhedron:- It is defined as the spatial arrangement of the ligands which are directly attached to the central metal ion/atom.
E.g. square planar, tetrahedral.
(v) Homoleptic:- Homoleptic compounds are defined as the compounds in which the donor/ligand attached to central metal atom/ion is of one kind.
E.g. and
(vi) Heteroleptic:- These are the coordination compounds in which central atoms are attached with more than one type of ligand.
E.g. and