1. Inorganic Chemistry (2)
Prepared by Dr. Hoda El-Ghamry
Lecturer of Inorganic Chemistry
Faculty of Science-Chemistry Department
Tanta University

2. Nature of Metal –Ligand bonding in complexes
To explain the nature of bonding in transition metal complexes, three different theories are generally used:
1- Valence bond theory (VBT)
2- Crystal field theory (CFT)
3- Ligand field theory (LFT) or Molecular orbital theory (MOT)
This theory is mainly due to Pauling. It deals with the electronic structure of the central metal ion in its ground state, kind of bonding, geometry(shape) and magnetic properties of the complexes. This is based on the following assumptions:

3. 1- The central metal atom or ion makes available number of empty s, p and d atomic orbitals equal to its coordination number. These vacant orbital
hybridise together to form bybride orbitals which are the same in number as the atomic orbitals hybridising together
2- The ligands have at least one σ-orbital containing a lone pair of electrons.
3-Vacant hybride orbitals of the metal atom or ion overlap with the filled σ-orbital s of the ligands to form ligand to metal σ bond (represented as L →M). This bond which is generally known as coordination bond is a special type of covalent bond and shows the characteristics of both the overlapping orbitals.

4. Geometrical shape: linear
1- sp hybridization
Example: [Ag(NH3)2]+
5s2 4d9 Ag [Kr]36
5s1 4d Ag [Kr]36
5s0 4d10 Ag [Kr]36 4d 5s 5p Ag 5s 5p 4d
Ag+ 5s 5p 4d
[Ag(NH3)2]+ XX XX
sp hyperidization
Geometrical shape: linear

5. 2- sp2 hybridization Example:[HgI3]- 4f14 5d10 6s2 6p0 Hg80 [Xe]54XX XX
Sp2 hyberidization
Geometrical structure: Trigonal planar

6. Geometrical structure: Tetrahedral
3- sp3 hybridization
Example: [NiCl4]2-
3d8 4s2 Ni [Ar]18
3d8 4s0 Ni [Ar]18 3d 4s 4p Ni 4s 4p 3d
Ni2+ 4s 4p 3d XX XX
[NiCl4]2-
Sp3 hyberidization
Geometrical structure: Tetrahedral

7. Geometrical structure: Square planar
4- dsp2 hybridization
Example: [Ni(CN)4]2-
3d8 4s Ni [Ar]18
3d8 4s0 Ni [Ar]18 3d 4s 4p Ni 4s 4p 3d
Ni2+ 4s 4p 3d
Pairing of
electrons 4s 4p 3d
[NiCl4]2- XX XX XX
dsp2 hybridization
Geometrical structure: Square planar

8. Geometrical structure: inner orbital octahedral structure
5- d2sp3 hybridization
Example: [Cr(NH3)6]3+
4S1 3d Cr [Ar]18
4S0 3d Cr [Ar]18 3d 4s 4p Cr 4s 4p 3d
Cr3+ 4s 4p 3d
[Cr(NH3)6]3+ XX XX XX
hybridization d2sp3
Geometrical structure:
inner orbital octahedral structure

9. Geometrical structure: outer orbital octahedral structure
6-sp3 d2hybridization
Example: [Co(H2O)6]2+
4S2 3d7 Co Co [Ar]18
الحالة المثارة S0 3d7 Co [Ar]18 3d 4s 4p Co 4s 4p 3d
Co2+ 4s 4p 4d
[Cr(NH3)6]3+ XX XX XX
تهجين من النوع sp3d2
Geometrical structure:
outer orbital octahedral structure