Chemistry » Transition Metals » Spectroscopic and Magnetic Properties of Coordination Compounds

Summarizing Spectroscopic and Magnetic Properties of Coordination Compounds

Key Concepts and Summary

Crystal field theory treats interactions between the electrons on the metal and the ligands as a simple electrostatic effect. The presence of the ligands near the metal ion changes the energies of the metal d orbitals relative to their energies in the free ion. Both the color and the magnetic properties of a complex can be attributed to this crystal field splitting.

The magnitude of the splitting (Δoct) depends on the nature of the ligands bonded to the metal. Strong-field ligands produce large splitting and favor low-spin complexes, in which the t2g orbitals are completely filled before any electrons occupy the eg orbitals. Weak-field ligands favor formation of high-spin complexes. The t2g and the eg orbitals are singly occupied before any are doubly occupied.

Glossary

crystal field splitting (Δoct)

difference in energy between the t2g and eg sets or t and e sets of orbitals

crystal field theory

model that explains the energies of the orbitals in transition metals in terms of electrostatic interactions with the ligands but does not include metal ligand bonding

eg orbitals

set of two d orbitals that are oriented on the Cartesian axes for coordination complexes; in octahedral complexes, they are higher in energy than the t2g orbitals

geometric isomers

isomers that differ in the way in which atoms are oriented in space relative to each other, leading to different physical and chemical properties

high-spin complex

complex in which the electrons maximize the total electron spin by singly populating all of the orbitals before pairing two electrons into the lower-energy orbitals

low-spin complex

complex in which the electrons minimize the total electron spin by pairing in the lower-energy orbitals before populating the higher-energy orbitals

pairing energy (P)

energy required to place two electrons with opposite spins into a single orbital

spectrochemical series

ranking of ligands according to the magnitude of the crystal field splitting they induce

strong-field ligand

ligand that causes larger crystal field splittings

t2g orbitals

set of three d orbitals aligned between the Cartesian axes for coordination complexes; in octahedral complexes, they are lowered in energy compared to the eg orbitals according to CFT

weak-field ligand

ligand that causes small crystal field splittings

[Attributions and Licenses]


This is a lesson from the tutorial, Transition Metals and you are encouraged to log in or register, so that you can track your progress.

Log In

Share Thoughts