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Chem20018: Reactions and Synthesis

Metal Ion Reactivity Tutorial 2

1. Consider the experimental observations below that relate to the solubilities of silver halides in water. Give an explanation for the dramatically different solubilities of the silver halides.

2. a) Draw the chemical structures of oxalic acid and 2,3-dimercaptopropanol

b) What is Minamata Disease?

c)  Based on the donor atoms present, which molecule out of oxalic acid and 2,3- dimercaptopropanol, would you recommend to treat mercury poisoning (chelation therapy)? Explain your answer.

3. a) Explain the following experimental observations:

Solid CuCl2.6H2O is dissolved in water. The mixture is analysed by mass spectrometry and the largest peak in the mass spectrum is at m/z = 85.5 Da. A small aliquot of this solution is added to a larger volume of D2O. One second after the addition, the D2O mixture is analysed by mass spectrometry and the largest peak in this mass spectrum is at m/z = 91.5 Da.

b) Would you expect a change to the mass spectrum on the same time scale (1 s) when [Cr(OH2)6]3+ was added to D2O? Explain your answer.

4. Consider the following ligand substitution reactions:

a) What is the d-electron count for platinum(II) in the complex [Pt(dien)OH2)]2+

b) Is [Pt(dien)OH2)]2+  diamagnetic or paramagnetic? Justify your answer

c) The rate of the reaction when L-  = Cl-  is significantly different to the rate when L-  = I- . Use this information to suggest a reaction mechanism for this reaction.

d) Suggest the experimental methodology that could be used to probe the reactions outlines in part c.

e) When L- = I-  would you expect reaction (i) or (ii) to be quicker? Explain your answer.

5. [Pt(NH3)2Cl2]  (cisPlatin) is an important anti-cancer agent. With the aid of  schematic diagrams show the changes to the coordination sphere that are important for its anti-cancer activity. State the likely ‘mechanism’ for each substitution process.

6. Discuss the “template effect” focusing on the synthesis of the macrocyclic tetraaza ligand called cyclam (shown below).

        7. The water exchange rates of transition metal ions cover several orders of magnitude.

a) Give one example of a kinetically labile metal ion and one example of a kinetically inert metal ion.

b) Briefly outline what factors contribute to lability (~1/4 page).