From four to five and six coordinated sparteine and α-isosparteine mononuclear Cu(II) complexes through the carboxylate donors

Abstract

Cu[(C 15H 26N 2)(OCOR) 2] complexes, where OCO is a fragment of either formato or acetato group and C 15H 26N 2 is sparteine or α-isosparteine have been synthesized and structurally characterized. The bis-formato complexes ( 1 and 2) display a distorted 4 + 1 coordination resulting from variable metal binding stereochemistry and function of the two formato units. The syn formato group acts as a pseudochelating bidentate while the anti conformer as a monodentate ligand. This inequivalence of the two formate ligands seems deliberate for it allows formation of the stabilizing intramolecular hydrogen bond between the CH donor belonging to the monodentate formate ligand and equatorially coordinated oxygen atom belonging to the pseudo-chelating formate ligand. At variance, the C 2 symmetrical bis-acetato complex ( 3) displays tetragonally elongated octahedral geometry of the CuN 2O 2O′O′ with long off-axis coordination of the second O atom from each acetate ligand in the axial position. Complexes 1– 3 have been also characterized by elemental analysis, IR, UV–Vis and MS spectroscopy.