25-08-2012, 09:46 AM
Coordination Chemistry
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Why Study Descriptive Chemistry of Transition Metals
Transition metals are found in nature
Rocks and minerals contain transition metals
The color of many gemstones is due to the presence of transition metal ions
Rubies are red due to Cr
Sapphires are blue due to presence of Fe and Ti
Many biomolecules contain transition metals that are involved in the functions of these biomolecules
Vitamin B12 contains Co
Hemoglobin, myoglobin, and cytochrome C contain Fe
Transition Metals
General Properties
Have typical metallic properties
Not as reactive as Grp. IA, IIA metals
Have high MP’s, high BP’s, high density, and are hard and strong
Have 1 or 2 s electrons in valence shell
Differ in # d electrons in n-1 energy level
Exhibit multiple oxidation states
Coordination Chemistry
Coordination sphere
Metal and ligands bound to it
Coordination number
number of donor atoms bonded to the central metal atom or ion in the complex
Most common = 4, 6
Determined by ligands
Larger ligands and those that transfer substantial negative charge to metal favor lower coordination numbers
Nomenclature: IUPAC Rules
Greek prefixes are used to indicate the number of each type of ligand when more than one is present in the complex
di-, 2; tri-, 3; tetra-, 4; penta-, 5; hexa-, 6
If the ligand name already contains a Greek prefix, use alternate prefixes:
bis-, 2; tris-, 3; tetrakis-,4; pentakis-, 5; hexakis-, 6
The name of the ligand is placed in parentheses
Structural Isomers
Coordination-sphere isomers
differ in a ligand bonded to the metal in the complex, as opposed to being outside the coordination-sphere
Stereoisomers
Optical isomers
isomers that are nonsuperimposable mirror images
said to be “chiral” (handed)
referred to as enantiomers
A substance is “chiral” if it does not have a “plane of symmetry”
[attachment=32677]
Why Study Descriptive Chemistry of Transition Metals
Transition metals are found in nature
Rocks and minerals contain transition metals
The color of many gemstones is due to the presence of transition metal ions
Rubies are red due to Cr
Sapphires are blue due to presence of Fe and Ti
Many biomolecules contain transition metals that are involved in the functions of these biomolecules
Vitamin B12 contains Co
Hemoglobin, myoglobin, and cytochrome C contain Fe
Transition Metals
General Properties
Have typical metallic properties
Not as reactive as Grp. IA, IIA metals
Have high MP’s, high BP’s, high density, and are hard and strong
Have 1 or 2 s electrons in valence shell
Differ in # d electrons in n-1 energy level
Exhibit multiple oxidation states
Coordination Chemistry
Coordination sphere
Metal and ligands bound to it
Coordination number
number of donor atoms bonded to the central metal atom or ion in the complex
Most common = 4, 6
Determined by ligands
Larger ligands and those that transfer substantial negative charge to metal favor lower coordination numbers
Nomenclature: IUPAC Rules
Greek prefixes are used to indicate the number of each type of ligand when more than one is present in the complex
di-, 2; tri-, 3; tetra-, 4; penta-, 5; hexa-, 6
If the ligand name already contains a Greek prefix, use alternate prefixes:
bis-, 2; tris-, 3; tetrakis-,4; pentakis-, 5; hexakis-, 6
The name of the ligand is placed in parentheses
Structural Isomers
Coordination-sphere isomers
differ in a ligand bonded to the metal in the complex, as opposed to being outside the coordination-sphere
Stereoisomers
Optical isomers
isomers that are nonsuperimposable mirror images
said to be “chiral” (handed)
referred to as enantiomers
A substance is “chiral” if it does not have a “plane of symmetry”