Palladium(II) catalysed cerium(IV) oxidation of mercury(I) in aqueous perchloric acid

Abstract

Palladium(II) is found to significantly catalyse the cerium(IV)-mercury(l) reaction in aqueous perchloric acid and the reaction follows the rate law<br /><br /> - <em>d</em>[Ce⁴⁺]_T/<em>d</em>t = <em>k</em>_a<em>k</em>_c[Ce(IV)][Pd(II)][Hg(I)]/<em>k</em>_b[Ce(III)]+<em>k</em>_c[Hg(I)]<br /><br /> which fits the two-step mechanism as shown below where a transient Pd(III) species takes part and <em>k</em>_a,<em> k</em>_b&nbsp;and <em>k</em>_c are the rate constants. <br /><br /> Ce(IV) + Pd(II) <img src="http://www.niscair.res.in/jinfo/equation102.gif" alt="" border="0" /> Ce(III) + Pd(III)<br /><br /> Pd(III) + Hg(I) <img src="http://www.niscair.res.in/jinfo/equation103.gif" alt="" border="0" /> Pd(II) + Hg(II)<br><br> The main active species of oxidant and catalysts and catalyst are found to be respectively HCe(SO₄)and PdCl⁺. The constants <em>k</em>_aand <em>k</em>_b/<em>k</em>_c have been evaluated.