Benniston L3-4 Flashcards
Describe water exchange rather for first row transition metals
The d3 ion has the slowest rate of exchange. The d4 ion appears to have the fastest rate of exchange but the d9 and d10 are fast as well. Fast water exchange rates are with all of the ions with a negative CFAE which is correct
Define a substitution reaction
Substitution reactions involve the replacement of a ligand coordinated to a metal by a free ligand in solution, or the replacement of a coordinate metal ion by a free metal ion
Describe what happens to oxidation state in a substitution reaction
There is no change in oxidation state of the metal ion during substitution but a change in oxidation state make take place as a result
Which two ways can ligand interchange in metal complexes
1) Combination of solvolysis and ligation
2) simple interchange
Describe solvolysis and ligation
The solvent is one of the reactants and replaces on of the ligands in the first step the the solvent will then get replaced by the new ligands
Describe simple interchange
No direct intervention of solvent
Which type of complexes is solvolysis and ligation mainly seen
Octahedral complexes
What type of complexes is simple interchange mainly seen
Square planar complexes
What are the 5 general mechanisms for substitution
- associative
- interchange associative
- interchange
- interchange dissociative
- dissociative
Describe the associative mechanisms
The entering groups binds to the reaction centre before bond weakening of the leaving group.
Describe the dissociative mechanisms
The leaving group has left the reaction centre prior to any interaction with the leaving group.
Describe the interchange associative mechanism (Ia)
The leaving group does not respond sufficiently fast to the approach of entering group and remains tight up to the point of the leaving group going.
Describe the interchange mechanism (I)
Both the ligand binding and leaving occur at the same time - half in half out
Describe the interchange dissociative
The leaving group is sensitive to the approach of the entering group
Give examples of good donating solvents
Water, acetonitrile, tetrahydrofuran and dimethylsulfozide
When is a solvolysis reaction important
Important when the solvent has a high affinity for a metal site
When is a direct replacement of one group for another preferred
Preferred by low oxidation state complexes in solvents of low coordinating power
