Question

[Rh(Cl)₅(OH₂)]^2- undergoes dissociative ligand exchange. Ratios of k-1/k2 were obtained as shown below/

I don't know the part C. Can you explain part C?

10) (10 marks) [Rh(ClI)s(OH2)]2- undergoes dissociative ligand exchange. Ratios of k-1/k2 were obtained as shown below. [Rh(Cl)5(OH2)]2. + X. Cl- N3- k-1/k2 62 7 (a) Do you expect kı and k-1 to change when X changes from Cl to N3? No (b) Provide a reasonable explanation for your answer in part (a). k1 k2 [Rh(Cl)512, + H2O- [Rh(Cl)5X]з-+ H2O > [Rh(Cl)5(OH2)]2 - X- k.1 k1 will depend only on [Rh(CI)s(OH2)]2. k-1 will depend on [Rh(CI)s]2 and H2O. Neither depends on the incoming ligand. ey What do the respective k1/k2 ratios indicate about the preference for Cl versus N3 ? Both Cl and N3" have ks/ke ratios of greater than 1, which means that [Rh(CI)s]2 has a greater preference for the dissociating ligand, H20, than either incoming ligand. However, the value of k1/k2 for Cl is significantly higher than for Na This means that [Rh(Cl)s]2- has a much stronger preference for Ns than for Cl.

Answer 1

Yes, Part (c) is quite easy! Not to worry about it!

In both the cases of having X = Cl^- and N₃^-, the ratio k_-1/k₂ > 1

When X = Cl^-, k_-1/k₂ = 62 (= 9*7)

i.e. k_-1 is 62 times greater than k₂.

And when X = N₃^-, k_-1/k₂ = 7

i.e. k_-1 is 7 times greater than k₂.

Therefore, [Rh(Cl)₅]^2- has a stronger preference (about 9 times) for Cl^- than for N₃^- to form [Rh(Cl)₅(X)]^3-