The ligation properties of some reduced Schiff base selena/telluraaza macrocycles: Versatile structural trends

The chalcogenaaza macrocycles 4, 5 and 6 show versatility in ligation properties towards various transition metal ions. The structure of the reduced 22-membered selenaaza macrocycle 4 (C32H36N4Se2) has been determined. The Ni-II complex 7 exhibits coordination by the N4Se2 donor sites. The Pd-II complexes 8, 9, 10, and 14 have been structurally characterized. The molecular structures of these complexes reveal interesting versatile ligating behaviors of the ligands. The Pd complexes 8, 9, and 14 display coordination by hard nitrogen donor atoms only, whereas the complex 10 showed coordination by N2Te2 donor centers. The Pt-II complex 11 shows the formation of a cationic metallamacrocycle with C-Pt-Se linkage. The crystal structures suggest that the coordination of metal atoms to donors is determined by the geometrical arrangement around the metal and by the conformation of the macrocycle rather than by the HSAB (hard/soft acid/base) principle. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006.