MU-PYRAZOLATO-MU-CARBOXYLATO-DIMANGANESE(II) AND DI(MU-PYRAZOLATO)DIMANGANESE(II) COMPLEXES - SYNTHESIS, CHARACTERIZATION AND CATALASE-LIKE FUNCTION

3,5-Bis[N,N-di(2-pyridylmethyl)aminomethyl]pyrazole (HL(1)) and 3,5-bis[N,N-bis(2-diethylaminoethyl)aminomethyl]pyrazole (HL(2)) found mu-carboxylato-dimanganese(II) complexes [Mn(2)L(O(2)CR][BPh(4)](2) (L = L(1), R = Ph; 1; L = L(2), R = Me 2) and 3,5-bis[N-(2-pyridylmethyl)aminomethyl]pyrazole (HL(3)) gave a di(mu-pyrazolato)-dimanganese(II) complex [Mn(2)L(2)(3)][BPh(4)](2) 3. The ditolune adduct of 3 crystallizes in the triclinic space group P (1) over bar with a = 14.452(3), b = 15.573(5), c = 10.988(4) Angstrom, alpha = 108.78(3), beta = 93.31(2) and gamma = 115.10(2)degrees. X-Ray diffraction analysis revealed a di(mu-pyrazolato)-dimanganese(II) core with Mn ... Mn separation 4.181(2) Angstrom. All the complexes showed catalytic activity towards disproportionation of H2O2 in dimethylformamide at 0 degrees C. The initial rate of dioxygen evolution in the presence of 1 is first order in both the complex concentration and that of H2O2; v = k[Mn-2][H2O2], k = 1.45 dm(3) mol(-1) s(-1). Together with the observation of a ligand-to-metal charge-transfer band characteristic of Mn-IV=O in the catalysis by 2, a mechanistic scheme involving a cycle from {Mn-III(OH)}(2) to {Mn-IV(=O)}(2) is inferred. In the disproportionation by 3 the initial rate of evolution is first order in complex concentration and second order in that of H2O2; v = k[Mn-2][H2O2](2) k = 29 dm(6) mol(-2) s(-1)).