Copper(II)-oxime complexes: A structural and spectroscopic study for a diamine dioxime ligand

The preparations are reported for copper(11) complexes with the ligand 4,4,9,9-tetramethyl-5,s-diazadodecane-2,l-dione dioxime, LH2. Syntheses from the syn (methyl) and anti isomers of the ligand give the same products. The complexes characterized are Cu(LH2)X2,yH2O (X = Cl-, ClO4-; y = 0, 1, 2) and Cu(LH)X (X = Cl-, Br-, ClO4-). The complex Cu(LH)Br is shown by X-ray structure analysis to contain dimeric units (Cu(LH))22+ with crystallographic C2 symmetry and with the copper atom in a trigonal bipyramidal coordination environment. Stability constants for the reactions Cu2+ + LH2 ←→ Cu(LH2)2+ (log K = 13.24 ± 0.05) and Cu(LH2)2+ ←→ Cu(LH)+ + H+ (log K = -3.24 ± 0.08) are reported, as well as the magnetic susceptibilities, i.r. spectra, and electronic absorption spectra of the complexes.