Oxo Transfer from Nitrogen Dioxide to Nitrito Group in a Copper(II) Complex

Reaction of Cu­(II) complex [CuII(LH)­(O2CCH3)2] (1) [LH = 4,6-ditert-butyl-2-((2-picolyl­(isopropyl)­amino)­methyl)­phenol] with equivalent amount of NO2 leads to the reduction of Cu­(II) to Cu­(I) with concomitant nitration at the phenol ring of the ligand. This resulted in the in situ formation of intermediate Cu­(I) complex of the nitrated ligand (L′H). Additional equivalent of NO2 coordinates to the Cu­(I) complex to form corresponding O-nitrito Cu­(II) complex [CuII(L′­(η1-ONO)] (2). Subsequent addition of NO2 led to the corresponding O-nitrato complex, [CuII(L′)­(η1-ONO2)] (3) with concomitant formation of NO. Complexes 2 and 3 were isolated and structurally characterized. The formation of NO in the reaction was established by spin-trapping experiment. Isotopic labeling experiment revealed that the oxo transfer takes place from NO2 to the coordinated η1-ONO group.