Oxidation of [Ru(NH3)5isn](BF4)2 by hyochlorous acid and chlorine in aqueous acidic media

UV-vis stopped-flow studies of the reaction of Ru(NH3)5isn](2+) (isn = isonicotinamide) with excess HOCl at 25 degrees C demonstrate that it proceeds in two time-resolved steps. In the first step Ru(NH3)5isn](3+) is produced with the rate law -dRu(II)]/dt = 2(aK(h)H(+)] + bH(+)]Cl(-)] + cCl(-)])HOCl](tot)Ru(II)]/(K(h) + H(+)]Cl(-)]). Here, K(h) is 1.3 x 10(-3) M(2) and corresponds to the equilibrium hydrolysis of Cl2, a is (8.34 +/- 0.19) x 10(3) M(-2) s(-1) and represents the acid-assisted reduction of HOCl, b is (4.04 +/- 0.13) x 10(4) M(-1) s(-1) and represents the reduction of Cl2, and c is (6.25 +/- 0.59) x 10(2) s(-1) and represents the Cl(-)-assisted reduction of HOCl. In the second step Ru(NH3)5isn](3+) undergoes further oxidation to a mixture of products with the rate law -dRu(III)]/dt = eRu(III)]HOCl]/H(+)] where e is (1.18 +/- 0.01) x 10(-2) s(-1). This step is assigned a mechanism with Cl(+) transfer from HOCl to Ru(III)(NH3)4(NH2)isn](2+) occurring in the rate-limiting step. These results underline the resistance of HOCl to act as a simple outer-sphere one-electron oxidant.