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

Reaction of Cu(II) complex [Cu(II)(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 [Cu(II)(L'(η(1)-ONO)] (2). Subsequent addition of NO2 led to the corresponding O-nitrato complex, [Cu(II)(L')(η(1)-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 η(1)-ONO group.