Mechanistic insights into nitric oxide generation from nitrite O-atom transfer in the unsymmetrical β-diketiminato copper(II) nitrite complex.

In this study, we employed DFT calculations to elucidate the mechanism of NO generation from nitrite PPh-induced oxygen atom transfer (OAT) in the unsymmetrical β-diketiminato copper(II), LCuONO. We discovered that the OAT process involves the cooperation of two PPh ligands and follows the mechanism distinct from that of the symmetrical β-diketiminato analogue. The Δ value, calculated to be 34.8 kcal mol, closely matches experimental data. The finding is further supported by analyzing the OAT product yields with varying equivalents of PPh. The penta-coordinated species 5a, with PPh occupying the axial site, forms in the final stage of the OAT process. The isomerization of 5a and the decoordination of the hemilabile pyridyl arm synergistically reduce Cu(II) to Cu(I), facilitating NO release from the Cu(I) centre. These computational results provide valuable insights for the ligand design for PPh-induced OAT reactions to produce NO in Cu(II) nitrite systems.