Question 1

In terms of reaction rates, what do complexes of majority of s block metals and complexes of M³⁺ ions of the f block have in common? A) They are both non-labile. B) They are both very labile. C) They have nothing in common.

Accepted Answer

Complexes of the majority of s block metals and complexes of M³⁺ ions of the f block are both very labile, meaning they can undergo reactions and exchange their ligands rapidly. This is due to the relatively low charge density of s block metal ions and the large size and variable coordination numbers of f block metal ions, which facilitate easy ligand exchange.

Question 2

Which mechanism takes place in one step only?&#10;A) associative&#10;B) dissociative&#10;C) interchange

Accepted Answer

Interchange mechanism takes place in one step only.

Question 3

What is rate-determining step?&#10;A) It is the slowest elementary step that dominates the rate law and speed of the reaction.&#10;B) It is the first step in the mechanism that determines the direction of reaction.&#10;C) It is any step that leads to an unstable reaction intermediate.

Accepted Answer

B

Question 4

Which of the following three Pt complexes is going to have the fastest substitution of Cl ligand? A) trans-[PtCl(H)(PEt₃)₂] B) trans-[PtCl(CH₃)(PEt₃)₂] C) trans-[PtCl(OH)(PEt₃)₂]

Accepted Answer

The trans effect of H^- > CH₃^- > OH^-. The stronger the trans effect of the ligand, the faster the substitution of the ligand trans to it.

Question 5

Steric strain (i.e. the presence of bulky ligands) in octahedral complexes favours __________ rate-determining step.&#10;A) associative&#10;B) dissociative&#10;C) interchange.

Accepted Answer

Steric strain in octahedral complexes favors a dissociative rate-determining step because the departure of a ligand creates more space in the coordination sphere, making it easier for bulky ligands to rearrange or for new ligands to approach and bind.

Question 6

Which of the following ligands should enable base-accelerated ligand substitution?&#10;A) bipyridyl&#10;B) acetylacetonato&#10;C) ethylenediamine

Accepted Answer

Ethylenediamine is a strong base and can deprotonate to form a nucleophilic amine, which can attack the metal center and promote ligand substitution.

Question 7

Identify the correct statement:&#10;A) If the reaction intermediate has square pyramidal geometry, the reaction proceeds with the retention of the initial geometry.&#10;B) If the reaction intermediate has trigonal bipyramidal geometry, the reaction proceeds with the retention of the initial geometry.&#10;C) If the reaction intermediate has square planar geometry, the reaction proceeds with the retention of the initial geometry.

Accepted Answer

The answer of Identify the correct statement:&#10;A) If the reaction...

Question 8

Identify the mechanism that is not applicable to the isomerisation of octahedral complexes.&#10;A) Bailard twist mechanism&#10;B) Berry pseudorotation mechanism&#10;C) Ray-Dutt twist mechanism.

Accepted Answer

The Berry pseudorotation mechanism is applicable to trigonal bipyramidal complexes, not octahedral complexes.

Question 9

Which of the following elementary steps is not part of the outer sphere electron transfer mechanism?&#10;A) association&#10;B) bridge formation&#10;C) diffusion.

Accepted Answer

Bridge formation is characteristic of the inner sphere mechanism, not the outer sphere mechanism. In the outer sphere mechanism, the electron transfer occurs without the formation of a chemical bridge between the reactants.

Question 10

Identify the correct statement:&#10;A) Square planar complexes react following the associative mechanism unless steric effects prevent association.&#10;B) The trans effect plays no role for ligand substitution in octahedral complexes.&#10;C) The rate-determining step in inner sphere electron transfer is very frequently the bridge formation step.

Accepted Answer

Square planar complexes, particularly those of d8 metals like Pt(II), often undergo ligand substitution via an associative mechanism, where a ligand approaches and forms a bond with the metal center before another ligand leaves. This is unless steric hindrance prevents the association of the incoming ligand.

Deck 21: Coordination Chemistry: Reactions of Complexes