[2] Metal Ligand Bonding In Transition Metal Complexes | Inorganic chemistry | BSc 3rd Year

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For Bsc 3rd year students

In Chemistry, a metal–ligand multiple bond describes the interaction of certain ligands with a metal with a bond order greater than one.Coordination complexes featuring multiply bonded ligands are of both scholarly and practical interest. Transition metal carbene complexes catalyze the olefin metathesis reaction. 

The Crystal Field Theory (CFT) is a model for the bonding interaction between transition metals and ligands. It describes the effect of the attraction between the positive charge of the metal cation and negative charge on the non-bonding electrons of the ligand. When the ligands approach the central metal ion, the degeneracy of electronic orbital states, usually d or f orbitals, are broken due to the static electric field produced by a surrounding charge distribution. CFT successfully accounts for some magnetic properties, colors, and hydration energies of transition metal complexes, but it does not attempt to describe bonding.

The electrons in the d orbitals of the central metal ion and those in the ligand repel each other due to repulsion between like charges. Therefore, the d electrons closer to the ligands will have a higher energy than those further away, which results in the d orbitals splitting in energy. This splitting is affected by:

the nature of the metal ion

the metal’s oxidation state (a higher oxidation state leads to a larger splitting)

the arrangement of the ligands around the metal ion

the nature of the ligands surrounding the metal ion

All of the d orbitals have four lobes of electron density, except for the dz2 orbital, which has two opposing lobes and a doughnut of electron density around the middle. The d orbitals can also be divided into two smaller sets. The dx2–y2 and dz2 all point directly along the x, y, and z axes. They form an eg set. On the other hand, the lobes of the dxy, dxz, and dyz all line up in the quadrants, with no electron density on the axes. These three orbitals form the t2g set. In most cases, the d orbitals are degenerate, but sometimes they can split, with the eg and t2g subsets having different energy.

video parts
part 1
   • [1] Metal Ligand Bonding In Transitio...  

part 2
   • [2] Metal Ligand Bonding In Transitio...   ( you are watching)
part 3
   • [3] Metal Ligand Bonding In Transitio...  

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