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

<div><p>The interactions of [Au(<i>cis</i>-DACH)Cl₂]Cl and [Au(<i>cis</i>-DACH)₂]Cl₃ [where <i>cis</i>-DACH is <i>cis</i>-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(<i>cis</i>-DACH)₂]Cl₃ are <i>k</i> = 18 M⁻¹s⁻¹, ∆<i>H</i>^≠ = 11 kJ M⁻¹, ∆<i>S</i>^≠ = −185 JK⁻¹ M⁻¹, and <i>E</i>_a = 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(<i>cis</i>-DACH)Cl₂]Cl are <i>k</i> = 148 M⁻¹s⁻¹, ∆<i>H</i>^≠ = 39 kJM⁻¹, ∆<i>S</i>^≠ = −80 JK^-1 M⁻¹, and <i>E</i>_a = 42 kJM⁻¹ along with SWV peak +0.82 V, indicating much higher reactivity of [Au(<i>cis</i>-DACH)Cl₂]Cl toward cyanide than [Au(<i>cis</i>-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.</p></div

Sub-acute toxicity, salient renal microscopic findings.

<p>Sub-acute toxicity, salient renal microscopic findings.</p

Microscopic pictures of renal tubules, with no evidence of necrosis as seen in sub-acute toxicity study of a gold (III) compound [Au(en)Cl₂]Cl, H&E at magnifications of : a. ×10. b. ×20. c. ×40.

<p>Microscopic pictures of renal tubules, with no evidence of necrosis as seen in sub-acute toxicity study of a gold (III) compound [Au(en)Cl₂]Cl, H&E at magnifications of : a. ×10. b. ×20. c. ×40.</p

Acute toxicity, salient hepatic microscopic findings.

*<p>Capsular inflammation with peritonitis was discerned in 40% of cases.(fibrinopurulent exudates on the surface).</p>**<p>An occasional microgranuloma was present in 20% of cases.</p

Spectrum of renal tubular necrosis seen in acute toxicity study of a gold (III) compound [Au(en)Cl₂]Cl.

<p>Spectrum of renal tubular necrosis seen in acute toxicity study of a gold (III) compound [Au(en)Cl₂]Cl.</p

Renal and hepatic tissues in the controls used in acute (a,b,c) and sub-acute (d,e,f) toxicity parts of study. a:

<p>Renal tissue showing mild congestion with no other pathological change as seen in acute toxicity controls (H&E x40). <b>b:</b> Hepatic tissue as seen in acute toxicity controls (H&E x40) showing mild congestion. No other pathological change is seen in this focus. <b>c:</b> Marked ballooning degeneration as seen in acute toxicity controls (H&E x40). <b>d:</b> Unremarkable renal tubules as seen in sub-acute toxicity controls (H&E x40). <b>e:</b> Unremarkable hepatic tissue as seen in sub-acute toxicity controls (H&E x20). <b>f:</b> Unremarkable hepatic tissue as seen in sub-acute toxicity controls (H&E x40).</p

Histological categorization of drug-induced hepatic lesions.

<p>Histological categorization of drug-induced hepatic lesions.</p

Microscopic findings of renal tubules showing different grades of renal tubular necrosis as seen in the acute toxicity study of a gold (III) compound [Au(en)Cl₂]Cl.

<p><b>a & b:</b> Grade 2 as seen in H&E ×20 and ×40. Necrotic tubules are seen amongst viable renal tubules. The necrosis is less than 25% of the total material examined. In ×40 magnification, more abundant, necrotic cells are seen along with normal renal tubules. <b>c & d:</b> Grade 1 as seen in H&E ×40 magnification. Scattered individual apoptotic/necrotic cells with strongly eosinophilic cytoplasm and pyknotic nuclei are seen. <b>e & f:</b> Grade 5 as seen in H&E ×20 and ×40 The entire field shows mostly necrotic renal tubules.</p

Spectrum of hepatic microscopic findings as seen in the acute toxicity study of a gold (III) compound [Au(en)Cl₂]Cl.

<p>a: Marked mixed micro and macrovesicular steatosis, H&E ×40. b & c: Marked sinusoidal congestion and dilatation, H & E ×20 and ×40 respectively. d: Marked ballooning degeneration along with two microgranulomas, H & E ×40.</p

Sub-acute toxicity, salient hepatic microscopic findings.

**<p>100% (6) cases revealed capsular inflammation.</p>***<p>16.66% (1) case revealed an occasional microgranuloma.</p