Nitric oxide reactivity of copper(II) complexes of bidentate amine ligands: effect of substitution on ligand nitrosation

Three copper(II) complexes with bidentate ligands L-1, L-2 and L-3 [L-1, N,N'-dimethylethylenediamine; L-2, N,N'-diethylethylenediamine and L-3, N,N'-diisobutylethylenediamine], respectively, were synthesized as their perchlorate salts. The single crystal structures for all the complexes were determined. The nitric oxide reactivity of the complexes was studied in acetonitrile solvent. The formation of thermally unstable [Cu-II-NO] intermediate on reaction of the complexes with nitric oxide in acetonitrile solution was observed prior to the reduction of copper(II) centres to copper(I). The reduction was found to result with a simultaneous mono-and di-nitrosation at the secondary amine sites of the ligand. All the nitrosation products were isolated and characterized. The ratio of the yield of mono-and di-nitrosation product was found to be dependent on the N-substitution present in the ligand framework.