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

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:

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.

Geometrical shape: linear 1- sp hybridization Example: [Ag(NH3)2]+ 5s2 4d9 Ag47 [Kr]36 5s1 4d10 Ag47 [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

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

Geometrical structure: Tetrahedral 3- sp3 hybridization Example: [NiCl4]2- 3d8 4s2 Ni28 [Ar]18 3d8 4s0 Ni2+ [Ar]18 3d 4s 4p Ni 4s 4p 3d Ni2+ 4s 4p 3d XX XX [NiCl4]2- Sp3 hyberidization Geometrical structure: Tetrahedral

Geometrical structure: Square planar 4- dsp2 hybridization Example: [Ni(CN)4]2- 3d8 4s2 Ni28 [Ar]18 3d8 4s0 Ni2+ [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

Geometrical structure: inner orbital octahedral structure 5- d2sp3 hybridization Example: [Cr(NH3)6]3+ 4S1 3d5 Cr24 [Ar]18 4S0 3d3 Cr3+ [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

Geometrical structure: outer orbital octahedral structure 6-sp3 d2hybridization Example: [Co(H2O)6]2+ 4S2 3d7 Co Co27 [Ar]18 الحالة المثارة 4S0 3d7 Co2+ [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