Complexes Flashcards
1
Q
How do transition metal ions form co-ordinate bonds?
A
by accepting electron pairs from ions or molecules
2
Q
What is a complex ion>
A
- when two, four, or six ligands bond to a single transition metal ion
3
Q
What is the co-ordination number
A
no. of co-ordinate bonds with ligands that surround the TM
4
Q
What is a ligand?>
A
- ion or mlecule w lone pair of electrons that forms a co-ordnate bond with a transition metal
- acts as as lewis base
5
Q
What are aqua ions?
A
- dissolve salt of a transition metal in water
- water acts as ligand
- usually in an octahedral arrangement
- such species are called aqua ions
6
Q
What are the different shapes of complex ions?
A
- octahedral
- co-ordination number of six
- most tetrahedral
- co-ordination number of four
- some square plane
- co-ordination number of four
7
Q
What are multidentate ligands?
A
- have more than one atom with a lone pair of electrons which can bind to a transition metal ion
8
Q
What are chelates?
A
- complex ions with polydenate ligands are called chelates
9
Q
What are chelates used for?
A
remove d-block metal ions from solutions
10
Q
What is EDTA?
A
- a hexadentate ligand
- iff added to a soln of a transition metal salt, the EDTA will replace all six water ligands
11
Q
What is the chelate effect?
A
- in reaction w a hexdentate ligand, e.g. EDTA, two species are replaced by 7
- 6 water molc released
- causes increase in entropy
- drives reaction to right
- chelate complexes w polydenate ligands are favoured over complexes w mondentate ligands
- this is the chelate effect
12
Q
What reasons are there for changes in shape?
A
- size of ligand forming bond
- e.g Cl > N, forms fewer ligands fit round central metal ions
13
Q
What cis and trans complexes
A
- no way for rotation to occur
- cis means the 2 of the same molc are next to eachother rather than opposite
14
Q
How does optical isomerism occur?
A
- two isomers than are non-superimposible mirror images
- occur when there are two or more bidentate ligands in a complex
- chiral
- idnetical properties
- different effect on polarised light
15
Q
Why does ammonia replace water?
A
- similar in size
- no change in co-ordination number
- reacts with hexaaqua ions in distinct ways because it acts as a base and a ligand
- metal hydoxide forms when lil bit of NH3 added
- when more added the ppt redissolves and ligan exchange reaction has occured
17
Q
Why does the ppt dissolve when ammonia added?
A
