Nitrite Reduction by Trinuclear Copper Pyrazolate Complexes: An Example of a Catalytic, Synthetic Polynuclear NO Releasing System.

Two trinuclear CuII pyrazolato complexes with a Cu3(μ3-E)-core (E = O2- or OH-) and terminal nitrite ligands in two coordination modes were characterized crystallographically, spectroscopically, and electrochemically. One-electron oxidation of the μ3-O species produces a delocalized, mixed-valent, formally CuII2CuIII-nitrite, but no nitrate. In contrast, under reducing conditions-addition of PhSH as an electron and proton donor-both complexes mediate the reduction of nitrite, releasing NO.