Mechanism of the two-electron reduction of trans-oxoaquaruthenium(IV) to trans-diaquaruthenium(II)

Abstract

The kinetics and mechanism of the reduction of trans-[RuIVL(O)(H2O)]2+ to trans-(RuIIIL(OH)(H2O))2+ (L = 6,7,8,9,10,11,17,18-octahydro-6,10-dimethyl-5H-dibenzo[e,n][1,4,8,12] dioxadiazacyclopentadecine) in aqueous solution by cis-[RuII(NH3)4(isn)2]2+ (isn = isonicotinamide) and of trans-[RuIIIL(OH)(H2O)]2+ to trans-[RuIIL(H2O)2]2+ by [RuII(NH3)4(bipy)]2+ (bipy = 2,2′-bipyridine) have been studied. The reactive intermediates are trans-[RuIVL(OH)(H2O)]3+ and trans-[RuIIIL(H2O)2]3+ respectively. The rate constants ke1 and ke2 for the reduction of trans-[RuIVL(OH)(H2O)]3+ and trans-[RuIIIL(H2O)2]3+ have been obtained and can be correlated with the Marcus cross-relation. The estimated self-exchange rate constants of the trans-[RuL(OH)(H2O)]3+/2+ and trans-[RuL(H2O)2]3+/2+ couples are 3.1 × 10-4 and 3.9 × 103 dm3 mol-1 s-1 respectively. The complex trans-[RuIIIL(OH)(H2O)][ClO4]2 has been characterised by X-ray crystallography: space group P1, a = 11.108(2), b = 11.683(1), c = 12.349(1) Å, α = 89.38(1), β = 64.81(1), γ = 71.44(1)° and Z = 2.