Transcript Slide 1

Polydentate Ligands &
Nomenclature
Chapter 24 – Lecture 2
Chemistry 123
Spring 2008
Dr. Woodward
Chelating (Polydentate) Ligands
Porphyrins
Porphine (C20H14N4)
Myoglobin &
Hemoglobin
Chlorophyll
Rules for Naming Coordination Compounds
1. For ionic compounds the cation comes before the anion.
2. For the complex ion part (within brackets) the ligands are listed
in alphabetical order before the metal.
3. Anionic ligands end in the letter o, neutral ligands retain their
names (NH3 = ammine, H2O = aqua).
Cl− = chloro
Br− = bromo
I− = iodo
OH− = hydroxo CN− = cyano
O2− = oxo
4. Greek prefixes are used to indicate the number of ligands
(different prefixes are used if the ligand itself has one of these prefixes).
2 = di
3 = tri 4 = tetra
5 = penta 6 = hexa
2 = bis 3 = tris 4 = tetrakis (alternate prefixes)
5. If the complex ion has a negative charge it ends in ate.
6. The oxidation number of the metal is given in parentheses in
roman numerals.
Color: CrO4- & Chromate Salts
1.2
5
conc.
CrO42solution
SrCrO4
1.0
PbCrO4
0.8
dilute CrO42solution
3
0.6
2
0.4
absorbance (SrCrO4, PbCrO4)
2-
absorbance (CrO4 )
4
1
0.2
0.0
250
300
350
400
450
500
550
600
650
0
700
wavelength (nm)
SrCrO4 behaves much like a concentrated CrO42- solution. Sr2+ ions have
little effect on the electronic absorption, whereas Pb2+ ions shift the
absorption edge to lower energy (longer wavelengths).