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CHY1301 - Fundamentals of inorganic chemistry > Stability constants > Flashcards

Stability constants Flashcards

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1
Q

What is a lewis base?

A

Ligand

Electron pair donor

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2
Q

What is a lewis acid?

A

Metal

Electron pair acceptor

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3
Q

What is binding affinity expressed as?

A

A numerical value

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4
Q

What is kinetic stability?

A

The rate of reaction

Whether something is labile or inert

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5
Q

What is thermodynamic stability?

A

The position of equilibrium which is measured using the equilibrium constant

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6
Q

Is there a correlation between kinetic and thermodynamic stability?

A

No

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7
Q

What is used to show kinetic stability?

A

small k

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8
Q

What is used to show thermodynamic stability?

A

large K

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9
Q

What do you measure the thermodynamic affinity of?

A

the ligand binding to the metal

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10
Q

What equation is used to calculate K?

A

K = [Products]/[reactants]

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11
Q

What is the binding of the ligand like when the value of K is large?

A

Tight binding

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12
Q

What is the binding of the ligand like when the value of K is small?

A

Weak binding

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13
Q

What value of K is favoured?

A

Large value of K

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14
Q

Due to stability constants usually being large, what is the more convenient way to measure them?

A

Use Log10(K)

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15
Q

What does K not tell you anything about?

A

Rate
There is no relationship to the rate of reaction
A large K does not mean ligands bind fast

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16
Q

What symbol is used for the formation constant?

A

β

17
Q

What would the general equation for K1 be?

A

K1 = [MLⁿ⁺] / [Mⁿ⁺][L]

18
Q

What would the general equation for K2 be?

A

K2 = [ML₂ⁿ⁺]/[MLⁿ⁺][L]

19
Q

What would the general formation constant be?

A

β = [ML₂ⁿ⁺]/[Mⁿ⁺][L]²

20
Q

How would you generate the formation constant?

A

Look at the starting and end concentrations and the amount of ligands used
Intermediates aren’t included

21
Q

If you expand the formation constant, what can you get?

A

The two K constants generated

β = K1 x K2

22
Q

What is the general order for the values of the stability constants?

A

K1>K2>K3>K4

23
Q

What are the three influencing factors for the value of β?

A

1) Sterics
2) Statistics
3) charge

24
Q

Which factor is the most important?

A

Sterics

25
Q

How do sterics effect β?

A

When you substitute a new ligand its usually bigger than the ligands that are already bound
This means if any more are added, they will be repelled by the larger ligand already substituted.
The repulsion causes the reaction to become more difficult

26
Q

What are statistics and how do they influence β?

A

As more ligands bind, this reduces the amount of variable sites available for the new ligands to bind

27
Q

When is charge a problem and effects β?

A

When anionic ligands are used

28
Q

What happens when you add 3 charged ligands to a positive complex?

A

The first one - Attracted to the complex to binds easily
The second one - binding to a neutral complex so there is no charge issue
The third one - binding to a negatively charged complex meaning that the anion will be repelled

29
Q

Which metal is an exception, having an unfavourable change in co-ordination number? Explain.

A

Hg

When a third ligand is added, K3 is low and K4 is high which doesn’t follow the trend

30
Q

What is the order for K values for spin states when adding large ligands such as bipy and phen?

A

K1>K2

31
Q

What is a chelate ring?

A

Ring made up of ligands, usually bidentate

32
Q

Why are chelate rings preferred?

A

They are more stable

Bidentate ligands bind tigheter to a metal than two similar monodentate ligands

33
Q

How do formation constants for bidentante ligands compare to monodentant ligands?

A

They are significantly larger

34
Q

How does the dissociation of monodentate ligands compare to the dissociation of bidentate ligands?

A

Monodentate ligands dissociation from the metal ion
For bidentate, the dissociated end cannot migrate away from metal ion. Migration requires simultaneous breaking of two bonds which is very unlikely

35
Q

How does the entropy of monodentate ligands compare to the entropy of bidentate ligands?

A

There is higher disorder and higher entropy for a reaction with bidentante ligands
2 molecules to 3 whereas monodentate ligands are 3 to 3

36
Q

What is the macrocyclic effect?

A

Multidentate ligands binding to one metal

37
Q

What are crown ethers?

A

Multiple oxygens joined to the metal centre

Different metals match different cavity sizes

38
Q

How is the best fit for a crown ether determined?

A

Highest K value

39
Q

What is the chelate effect mostly?

A

Entropic in nature

CHY1301 - Fundamentals of inorganic chemistry (36 decks)

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