Download 23.2 - Transition-Metal Complexes 23.3

Unit 23: Coordination Chemistry
23.2 - Transition-Metal Complexes
Metal Complexes: Species that are assemblies of a central transition-metal ion bonded to a group of surrounding molecules or ions
Ligand - The molecules or ions bonded to the metal ion in a complex
Coordination Number - Number of atoms bonded to the metal ion
Coordination Sphere - Central metal and the ligands
23.3 - Common Ligands
Donor Atom - The ligand atom that binds to the central metal ion
Chelating Agents - Bidentate and polydentate ligands
Chelate Eect - Formations constants are larger for bidentate and polydentate ligands
Porphyrins are important in biomolecules
For example, chlorophyll has a porphyrin with magnesium in the center
(en) is bidentate
EDTA has a coordination number of 6
Larger ligands lower coordination number
Ligands that transfer substantial negative charge to the metal ion lower coordination number
23.4 - Nomenclature and Isomerism
1) For ionic complexes, name the cation rst
2) Names of ligands are put in alphabetical order before the name of the metal
3) Names of anionic ligands end with -o, while neutral ligands have a group of special names
4) Use prexes to denote the number of simple ligands (if the name of the ligands already has such a prex,
use alternate prexes of bis, tris, tetrakis, etc.)
5) For complex anions, add -ate to the Latin name of the metal
6) Give the oxidation number of the metal
*In complex anions (negative charge), copper, gold, iron, and platinum change names to old names
*Put parentheses around the complex if there are multiples with an alternate prex: tris(ethylenediamine)
Isomers - Same composition but dierent arrangement
Structural Isomer - Dierent bonds
Linkage Isomerism - If a ligand can bind to the metal with one or another atom as the donor atom
Coordination Sphere Isomerism - Dier in which ligands are bonded to the metal and which are outside the
coordination sphere
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Stereoisomer - Same bonds but dierent ways in which the ligands occupy the space
Geometric (Diastereoisomers) Isomerism - Arrangement of the atoms is dierent but the same bonds are
present
Optical Isomerism - These are enantiomers, which are mirror images that cannot be super-imposed on one
another
Tetrahedrals cannot form geometric isomers since it's the same when viewed from any side
Chelating agents can't span across the coordinate sphere, which limits the number of isomers
Chiral - Not super-imposable with no plane of symmetry
Square planars are not chiral since they are at
Tetrahedrals are chiral if all four ligands are dierent
Chiral molecules interact the same way as usual except when they interact with other chiral molecules
A mixture of equal amounts of L and D isomers is a racemic mixture
23.5 - Color and Magnetism
Small molecules and ions that obey the octet rule are colorless
Metal ions with completed electronic subshells are usually colorless
Large organic molecules with conjugated systems are colored
Metal ions with a partially lled d or f level are colored
3d metals with high oxidation numbers are colored
If a substance absorbs a certain kind of light, it appears to have its complementary color
Diamagnetic - Very weak repulsion from magnetic eld (all electrons paired)
Paramagnetic - Weak attraction to magnetic elds (one or several unpaired electrons)
Ferromagnetic - Strong attraction to magnetic eld (many unpaired electrons organized in a crystal)
High Spin - Many unpaired e−
Low Spin - Many paired e−
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