Isomerism & Crystal Field Isomerism & Crystal Field TheoryTheory
Chapter 24 – Lecture 3Chapter 24 – Lecture 3
Chemistry 123Spring 2008
Dr. Woodward
IsomersIsomers
Different ligands
make bonds to the metal
Ligands bond to the metal
through different atoms
Ligands have
different (ligand)
neighbors
Molecules are non-
superimposable mirror images
Linkage IsomersLinkage Isomers
Geometric IsomersGeometric Isomers
Optical IsomersOptical Isomers
Intra-atomic (d to d) excitationsIntra-atomic (d to d) excitations
In these complexes the color comes from absorption of light that leads to excitation of an electron from one d-orbital to a different d-orbital on the same metal cation.
CuSO4NiSO4CoSO4FeSO4MnSO4 ZnSO4
[M(H[M(H22O)O)66]]n+n+ Complex ions Complex ions
MMHH22OO
MOMO66 Octahedron Octahedron
ddzz22 & d & dxx22-y-y22 orbitals (e orbitals (egg))• Point directly at the ligands • Stronger (repulsive) interaction with the ligands
Crystal Field Splitting Crystal Field Splitting (Octahedron)(Octahedron)
ddzz22 ddxx22-y-y22
ddxyxy ddyzyz ddxzxz
Electrons in d-orbitals are repelled from the electrons in the ligands. The repulsion is stronger for electrons
in d-orbitals pointing directly at the ligands.
En
erg
y
ddxyxy, d, dyzyz & d & dxzxz orbitals orbitals (t(t2g2g))• Point between the ligands • Weaker (repulsive) interaction with the ligands
Energy Levels of d-orbitals in an Energy Levels of d-orbitals in an octahedronoctahedron
ddxyxyddyzyz ddxzxz ddz2z2 ddx2-y2x2-y2
ddxyxy ddyzyz ddxzxz ddz2z2 ddx2-y2x2-y2
Free Cr3+ ion
Cr3+ ion with a spherical crystal
field
Cr3+ ion in an octahedral crystal field
En
erg
y
ddxyxy ddyzyz ddxzxz
ddz2z2 ddx2-y2x2-y2
Electronic ExcitationElectronic Excitation
ddxyxy ddyzyz ddxzxz
ddzz22ddxx22-y-y22
t2g
eg
= Crystal Field Splitting Energy
En
erg
y
ddxyxy ddyzyz ddxzxz
light (photon)
ddzz22ddxx22-y-y22
0.0
0.1
0.2
0.3
0.4
0.5
0.6
250 300 350 400 450 500 550 600 650 700 750
Wavelength (nm)
Abs
orba
nce
[Cr[Cr3+3+(H(H22O)O)66]]3+3+ Absorption Spectra Absorption Spectra
Nonbonding Metal d MO’s
Antibonding (*) Metal-Ligand MO’s
oct
Recommended
![for · 1. The type of isomerism shown by the complex [CoCl 2 (en) 2] is (1) Geometrical isomerism (2) Linkage isomerism (3) Ionization isomerism (4) Coordination isomerism Answer](https://img.pdfslide.us/doc/110x75/5ea5e4a5a62be97117265dc3/for-1-the-type-of-isomerism-shown-by-the-complex-cocl-2-en-2-is-1-geometrical.jpg)
