Reactivity of Mn(II) and Cu(II) adducts containing 2,6-dimethylpyridine N-oxide with SO2

Adducts of accurate formula MX2(2,6-MepyO)(2)(H2O)(n) (M = Mn, Cu; 2,6-Mepy O = 2,6-dimethylpyridine N-oxide; X = Cl, Br, I and NO3; n = 0, 2, 3, 6) re act with SO2 in the solid state and in toluene slurries at room temperature to yield SO2 adducts of different stoichiometry. The medium of the reactio n influences the ability of the adducts to bind sulphur dioxide and which u sually can retain a greater quantity of SO2 in toluene slurries than in the solid stare. An increase in the temperature disfavours the reaction in the solid state. Desorption studies were performed in order to postulate a coo rdination mode for the bound sulphur dioxide. This study, as well as analyt ical and spectroscopic data, allow us to suggest that the SO2 is bridging b etween metal centres and/or is bound to the neutral ligand (mean) in most o f the SO2 adducts.