The formation constants of some metal complexes with 3-Acetyl-4-hydroxycoumarin, dehydroacetic acid, and their oximes

The formation constants (K1, K2, and β2) of the complexes of 3-acetyl-4- hydroxycoumarin (ahc) and dehydroacetic acid (dha) and their respective oximes, ahco and dhao, with iron(II), cobalt(II), nickel(II), copper(II), zinc(II), calcium(II), magnesium(II), cadmium(II), dioxouranium(VI), iron(III), aluminium(III), scandium(III), indium(III), yttrium(III), and lanthanon(III) ions (lanthanum to lutetium inclusive with the exception of promethium) have been determined pH-metrically at 35� in 50% v/v aqueous dioxan medium with 0.100M sodium perchlorate as the constant ionic concentration, using Calvin and Wilson's pH-metric technique. The trends in the formation constants of these complexes are discussed. It is observed that, except in the case of Co2+, Ni2+, and Cu2+ ions, for which chelation through nitrogen donors is more favoured, all other ions prefer coordination through oxygen donors.