Ligand exchange mechanisms

Question 1

Name the Four kinds of ligand exchange mechanism?

Answer 1

1) Associative
2) Dissociative
3) Associative Interchange (Ia)
4) Dissociative Interchange (Id)

Question 2

What is the equation for an associative mechanism?

Answer 2

LnMX + Y —> LnMXY —> LnMY + X

Contains an intermediate with a higher coordination number

Question 3

What is the equation for an dissociative mechanism?

Answer 3

LnMX + Y —> LnM + X + Y—> LnMY + X

Question 4

What is the equation for an interchange mechanism?

Answer 4

LnMX + Y —> LnM(X+Y) —> LnMY + X

Question 5

What does the middle step of an interchange mechanism represent?

Answer 5

A non detectable intermediate i.e. A transition state

• Both bond making and breaking occurring at the same time

Question 6

In an interchange mechanism if the rate is more sensitive to the entering group (Y) than the leaving group X, what is the implication of this and what is it known as?

Answer 6

Implies both the entering and leaving group are strongly bound in the transition state

Associative Interchange (Ia)

Question 7

In an interchange mechanism if the rate is less sensitive to the entering group (Y) than the leaving group X, what is the implication of this and what is it known as?

Answer 7

Implies both the entering and leaving group are weakly bound in the transition state

Dissociative Interchange (Id)

Question 8

In the Eigen-Wilkins mechanism the incoming ligand inserts itself into the solvent cage forming what kind of complex before an interchange mechanism is carried out?

Answer 8

Am Encounter Complex

Question 9

An associative mechanism E.G the substitution of a 4 coordinate square planar Pt(II) can proceed via two types of pathway. Name them?

Which of these will be faster?

Answer 9

Associative and Salvation Pathways

Depends on the rates of each individual pathway, if salvation&raquo_space; associative then it becomes involved

Question 10

What is the name of the special type of mechanism that occurs for the hydrolysis of amine complexes>

Answer 10

Dissociative Conjugate Base (D-CB)

Question 11

What two effects combine to produce the Trans effect?

Answer 11

1) Polarisation effect
2) Pi-Component