DM - Complex ions Flashcards
What are complex ions?
Metal ions surrounded by ligands.
What is a complex (complex ion)?
A central metal atom or ion surrounded by coordinately bonded ligands.
What is a coordinate bond?
A dative covalent bond.
A covalent bond in which both electrons in the shared pair come from the same atom.
Where do both electrons come from in a coordinate bond in a complex?
The ligands.
What is a ligand?
An atom, ion or molecule that donates a pair of electrons to a central transition metal ion to form a coordinate (dative covalent) bond.
How do ligands form bonds?
Using lone pairs of electrons.
What must a ligand have to be able to bond?
At least one lone pair of electrons, or it won’t have anything to form a coordinate bond with.
What are ligands with one lone pair called?
Monodentate (or unidentate).
What are monodentate (or unidentate) ligands?
Ligands with one lone pair.
What are ligands with two lone pairs called?
Bidentate.
What are bidentate ligands?
Ligands with two lone pairs.
What can bidentate ligands do?
Can each form two coordinate bonds with a metal ion.
What are ligands with more than two lone pairs called?
Polydentate.
What are polydentate ligands?
Ligands with more than one lone pair.
Examples of monodentate/unidentate ligands
H2O (lone pair of e- on oxygen)
NH3 (lone pair on N)
Cl- (lone pair on Cl)
CN- (lone pair on C)
Examples of bidentate ligands
Ethanedioate (lone pairs on O’s)
Ethylenediamine (lone pair on N’s)
What is the bidentate ligand ethylenediamine often abbreviated to?
‘en’
Examples of polydentate ligands
EDTA^4- (6 lone pairs so it’s a hexadentate - can form 6 coordinate bonds with a metal ion).
What is the coordination number?
The number of coordinate (dative) bonds that are formed with the central metal ion.
What are the usual coordination numbers?
6 and 4.
What is the coordination number likely to be if the ligand is small - e.g. H2O or NH3?
6 - as 6 can fit around the central metal ion.
What is the coordination number likely to be if the ligand is larger - e.g. Cl-?
4 - as only 4 can fit around the central metal ion.
What shape does 6 coordinate bonds mean?
- Bond angles???
Octahedral.
90 degree bond angles.
What shape does 4 coordinate bonds usually mean?
- Bond angles???
Tetrahedral.
109.5 degree bond angles.
But occasionally:
Square planar.
90 degree bond angles.
