Explain with two examples each of the following:
Coordination entity, ligand, coordination number, coordination polyhedron, homoleptic and heteroleptic.
Explain with two examples each of the following:
Coordination entity, ligand, coordination number, coordination polyhedron, homoleptic and heteroleptic.
(i) Coordination entity A central metal atom or ion bonded to fixed number of molecules or ions (ligans) is known as coordination entity. For example [CoCl3(NH3)3],[Ni(CO)4],
(ii) Ligand The ions or molecules bound to the central atom/ion in the coordination entity are called ligands. These may be (a) Simple ions Such as CI, (b) Small molecules such H2O or NH3, (c) large molecules such as H2NCH2CH2NH2 or N(CH2CH2NH2)3 or even
(d) macromolecules, such as proteins.
On the basis of the number of donor atoms available for coordination, the ligands can be classified as:
(b) Bidentate Two donor atoms, e.g., H2NCH2CH2NH2 (ethane- 1,2-diamine or en), C2O24 (oxalate), etc.
(c) Polydentate More than two donor atoms, e.g., N(CH2CH2NH2)3 EDTA, etc.
(iii) Coordination number The coordination number (CN) of a metalion in a complex can be defined as the number of ligands or donor atoms to which the metal is directly bonded. e.g., In[PtCl6]2− CN of Pt = 6; In[Ni(NH3)4]2+, CN of Ni = 4.
(iv) Coordination polyhedron The spatial arrangement of the ligand atoms which are directly attached to the central atom or ion is called coordination polyhedron about the central atom. Octahedral, square planar, tetrahedral are some common coordination polyhedron.
e.g., [Co(NH3)6]3+ is octahedral; [NI(CO)4] is tetrahedral; [PtCl4]2− is square planar.
Where the M represents the metal atom and the L represents the ligands.
i.e.,
(v) Homoleptic Complexes in which a metal is bound to only one kind of donor groups are called homoleptic complexes.
e.g., [Co(NH3)6]3+
(vi) Heteroleptic Complexes in which a metal is bound to more than one kind of donor groups are known as heteroleptic complexes.
e.g., [Co(NH3)4Cl2]
(i) Coordination entity A central metal atom or ion bonded to fixed number of molecules or ions (ligans) is known as coordination entity. For example [CoCl3(NH3)3],[Ni(CO)4],
(ii) Ligand The ions or molecules bound to the central atom/ion in the coordination entity are called ligands. These may be (a) Simple ions Such as CI, (b) Small molecules such H2O or NH3, (c) large molecules such as H2NCH2CH2NH2 or N(CH2CH2NH2)3 or even
(d) macromolecules, such as proteins.
On the basis of the number of donor atoms available for coordination, the ligands can be classified as:
(b) Bidentate Two donor atoms, e.g., H2NCH2CH2NH2 (ethane- 1,2-diamine or en), C2O24 (oxalate), etc.
(c) Polydentate More than two donor atoms, e.g., N(CH2CH2NH2)3 EDTA, etc.
(iii) Coordination number The coordination number (CN) of a metalion in a complex can be defined as the number of ligands or donor atoms to which the metal is directly bonded. e.g., In[PtCl6]2− CN of Pt = 6; In[Ni(NH3)4]2+, CN of Ni = 4.
(iv) Coordination polyhedron The spatial arrangement of the ligand atoms which are directly attached to the central atom or ion is called coordination polyhedron about the central atom. Octahedral, square planar, tetrahedral are some common coordination polyhedron.
e.g., [Co(NH3)6]3+ is octahedral; [NI(CO)4] is tetrahedral; [PtCl4]2− is square planar.
Where the M represents the metal atom and the L represents the ligands.
i.e.,
(v) Homoleptic Complexes in which a metal is bound to only one kind of donor groups are called homoleptic complexes.
e.g., [Co(NH3)6]3+
(vi) Heteroleptic Complexes in which a metal is bound to more than one kind of donor groups are known as heteroleptic complexes.
e.g., [Co(NH3)4Cl2]
