Common and less-common coordination modes of the typical chelating and heteroaromatic ligands

Data on the different modes of bonding the metals to the most widely spread chelating [beta-diketones, o-oxyazomethines, o-oxy(mercapto) derivatives of azoles and azines] and heteroaromatic ligands are generalized and systematized. It is shown that, besides the common beta-diketonates, aldiminates, phenolates and mercaptophenolates structures, these complex compounds exhibit less-common modes of coordination. Five- and six-membered heterocycles form sigma- as well as pi-complexes. (C) 1998 Elsevier Science S.A.