Coordinated cations in dipicolinato complexes of divalent metal ions

Several salts of alkali, alkaline earth metal and organic ammonium cations of a complex anion [ML2]2− {Where L = dipicolinato dianion, M = copper(II), nickel(II) and zinc(II)} are prepared. The coordination effect of [ML2]2− with the cations such as sodium, potassium, calcium, magnesium, and organic cations namely diammonium cation of 1,5-pentanediamine, diammonium cation of 1,8-octyldiamine, mono ammonium cation of 4-aminobenzylamine are studied by determining their X-ray crystal structures. Depending on the nature of cations, four different types of structures are obtained. When calcium is the cation a polymeric structure with calcium ions bridging the [ML2]2− is observed. The salts having sodium and potassium cations form polymeric chain like structures by oxo and aqua bridges. In the case of magnesium, the hydrated form of magnesium cations coordinates to [ML2]2−. The organic ammonium salts of [ML2]2− have the structural features of conventional ionic complexes. These salts easily exchange cations. The organic ammonium salts of [ML2]2− decomposes to give the corresponding metal oxides at relatively low temperature range 300–450 °C.