Benniston L6

Question 1

Describe the inner sphere mechanism

Answer 1

the mechanism relies on the diffusion controlled association of the reductant and the oxidant. This is followed by a substitution reaction where the ligand of the oxidant penetrates the coordination sphere of the reductant

Question 2

What does the inner sphere mechanism require

Answer 2

requires:
- one of the reactants to be coordinately unsaturated
Or
- one reactant to be labile to dissociation

Question 3

What effects the inner sphere mechanism

Answer 3

bond strengths

Question 4

How does bond strengths effect the inner sphere mechanism

Answer 4

as part of the mechanism the bridged intermediate must break apart and so the strength of the M-L bod need to be considered.
The stronger the M-l bond the slower the reaction
hard-hard strong bond
Soft-soft strong bond
Hard-soft preferred

Question 5

Describe the importance of the bridging ligand in inner sphere mechanism

Answer 5

the bridging ligands must be important since it is the mediator for electron exchange and it keeps the metal ions within close proximity

Question 6

What are the two possible roles of the bridge

Answer 6

resonance transfer
Chemical transfer

Question 7

Describe resonance transfer

Answer 7

The electron is transferred directly from one metal to the other

Question 8

Describe chemical transfer

Answer 8

the electron hops to the bridge and then to the metal

Question 9

When would a chemical transfer or resonance transfer happen

Answer 9

we might expect that chemical transfer is preferred when x is an easily reduced ligand. However with non reducible ligands such as HO-, CN-, NCS- mechanism is consistent with a resonance transfer

Question 10

Define bridging ligand flexibility

Answer 10

Bridging ligand flexibility refers to how easily a ligand can bend, rotate, or adjust its length to connect two metal centers during inner sphere electron transfer

Question 11

Are rigid pi systems good bridging ligands

Answer 11

Rigid π-bridges keep metals in a fixed, favorable geometry good electron transfer

Question 12

Are alkyl chains good bridging ligands

Answer 12

Flexible aliphatic chains - can bend, but too flexible may insulate. Might let metals drift too far or misalign

Question 13

Describe halide bridges

Answer 13

Bridging halides (Cl⁻, Br⁻): Small and adaptable often ideal bridges

Question 14

Describe the outer sphere mechanism

Answer 14

outer sphere mechanism proceeds when on of the reactant is inert and does not contain a bridging ligand, electron transfer occurs through solvent