Adam A.A. Seliman

NMR and kinetic studies of the interactions of [Au(cis-DACH)Cl2]Cl and [Au(cis-DACH)2]Cl3 with potassium cyanide in aqueous solution

The interactions of [Au(cis-DACH)Cl2]Cl and [Au(cis-DACH)2]Cl3 [where cis-DACH is cis-1,2-diaminocyclohexane] with enriched KCN were carried out in CD3OD and D2O, respectively. The reaction pathways of these complexes were studied by 1H, 13C, 15N NMR, UV spectrophotometry, and electrochemistry. The kinetic data for the reaction of cyanide with [Au(cis-DACH)2]Cl3 are k = 18 M−1s−1, ∆H≠ = 11 kJ M−1, ∆S≠ = −185 JK−1 M−1, and Ea = 13 kJ M−1 with square wave voltammetric (SWV) peak +1.35 V, whereas the kinetic data for the reaction of cyanide ion with [Au(cis-DACH)Cl2]Cl are k = 148 M−1s−1, ∆H≠ = 39 kJM−1, ∆S≠ = −80 JK-1 M−1, and Ea = 42 kJM−1 along with SWV peak +0.82 V, indicating much higher reactivity of [Au(cis-DACH)Cl2]Cl toward cyanide than [Au(cis-DACH)2]Cl3. The interaction of these complexes with potassium cyanide resulted in an unstable [Au(13CN)4]− species which readily underwent reductive elimination reaction to generate [Au(13CN)2]− and cyanogen. Graphical Abstract