Year 13 - Complex ion formation and the shape of complex ions Flashcards
Name the bond formed between a transition metal ion and a ligand.
A coordinate bond.
What is the official name of the ion or molecule with a lone pair of electrons that forms a coordinate dative bond with a transition metal.
A ligand eg, H2O, NH3, Cl.
What do you call the number which describes the number of coordinate bonds formed.
The coordination number.
Give the corresponding names for the ions with the subsequent amount of bonds.
Co-ordination number 4 - often called tetrahedral eg. (CoCl4)2-
Co-ordination number 4 - sometimes can be square planar (NiCN4)2-
Co-ordination number 6 - often octahedral eg. (Co(NH3)6)3+
What are aqua ions?
When you dissolve the salt of a transition metal in water the positively charged metal ion becomes surrounded with water molecules acing as ligands. Often form octahedral arrangement.
What is a multidentate ligand?
When an ion or molecule has more than one lone pair of electrons and so can make multiple coordinate bonds to a transition metal ion.
Give examples of some bidentate ligands.
Ethane-1,2-diamine (or 1,2-diaminoethane) - each nitrogen has a lone pair which can form a coordinate bond to the metal ion - neutral ligand
The ethanedioate (oxalate) ion C204 2-
Benzene-1,2-diol - neutral ligand
EDTA4- - can act as a hexadentate ligand using lone pairs on four oxygens and both nitrogen atoms.
What is the official name for complex ions with polydentate ligands.
They are called chelates.
What is it called when you add a hexadentate ligand to a solution of transition metal salt?
If EDTA for example was added then it would replace the 6 water ligands. This would mean that on the left side of the equation there’d only be 2 species (the ligand complex and the EDTA) however on the right side there’d be the complex and the 6 replaced water molecules. This would mean that 2 species has been replaced by 7. This increase in the number of particles causes a significant increase in entropy which drives the reaction to the right. Chelate complexes with polydentate ligands are therefore preferred over monodentate ligands - the chelate effect.
