Preparation and properties of cobalt(III) complexes with a tripod N, N-bis(3-aminopropyl) glycinato quadridentate ligand

Abstract

The new complexes mer(N)-[ Co(5- dptma) (NO) 2) 2], [ CoCl 2(5- dptma)] ∗d H 2 O , mer( N)-[CoCl(5-dptma)(H 2O)] X = ClO 4 −, Br − and NO 3 −, fac(N)-[ Co(CO 3)(5- dptma)] ∗d 2 H 2 O, mer(N)-[ Co(CO 3)(5- dptma)] ∗d 5 H 2 O , fac(N)-[ Co(5- dptma) (hfac)]ClO 4 ∗d CH 3 OH and mer( N)-[Co(5-dptma)(hfac)]ClO 4, where H(5-[ rmdptma]) = N, N-bis(3-amino-propyl)glycine and H(hfac) = hexafluoro-2, 4-pentanedione, were prepared and most of them were characterized by UV-vis and NMR spectra. Two of the complexes with the hfac ligand show a pH-dependent, rapid and reversible colour change in water and in methanol, which is ascribed to a reversible addition of the lyate anion to one of the carbonyl carbon atoms of the coordinating hfac ligand. The equilibrium constants were estimated spectrophotometrically. The carbonato complexes decarboxylate in acid with retention of configuration and may be useful as starting materials for the preparation of further complex derivatives.