Solution Equilibria and Redox Reactivities of a Dioxo-bridged Manganese Complex

Article abstract of DOI:10.1039/DT9950000621

The dinuclear complex <(bipy)2Mn(III)O2Mn(IV)(bipy)2>(3+) (bipy = 2,2'-bipyridyl) 1 was stabilised in bipy-Hbipy(+) buffer where it coexists with the diaqua derivative <(H2O)2Mn(III)O2Mn(IV)(bipy)>(3+) 2 (equilibrium constant K^H).Reduction of 1 by NO2(-) has been found to be kinetically insignificant, but that of 2 is rapid, quantitative and follows the sequence Mn(III)Mn(IV) <*> (Mn(III))2 <*> Mn(II)Mn(III) <*> 2Mn(II).In the presence of an excess of NO2(-), first-order kinetics was observed at 830 nm, but a biphasic profile at 525 nm.At 30.0 deg C and I = 1.0 mol dm^-3, k₁K^H₁ and K₂K^H₂ are 34.9 +/- 0.8 and 3.3 +/- 0.2 dm³ mol^-1 s^-1 respectively.Added bipy retards, while Mn(2+) accelerates, the reaction.The solution equilibria are much more complex for 1 in HNO3 and H3PO4, but the known solution chemistry of 1 in such different media may be correlated by a unified reaction scheme.

Full text of DOI:10.1039/DT9950000621

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