Cu(2+) and Pt(2+) complexes of pyrazole and triazole based dinucleating ligands

A series of pyrazole and triazole based dinucleating ligands have been synthesized and their complexation potential for metal ions, which exhibit square planar coordination geometry has been studied. In the case of Cu(2+) the complexation equilibria in solution have been determined using pH titrations. Species with 1 : 1 stoichiometry CuLH(n)], 2 : 1 stoichiometry Cu(2)LH(m)], and of dimeric nature Cu(2)L(2)H(p)], have been detected and their overall stability constants have been measured. The reactivity of the dinuclear species Cu(2)LH(-1)] towards phosphate ester hydrolysis have shown that the OH-functionality incorporated in some of the ligands does not enhance the hydrolysis rate. Several ligands were reacted with Pt(2+) to give insoluble dinuclear species Pt(2)LI(3)]. One of them was studied by X-ray diffraction and shows that the two Pt(2+) are bridged by the pyrazolide group and by one I(-). The remaining two positions are occupied by the amino group in alpha position of the heterocyclic ring and a terminal I(-). The nearly planar Pt(2)LI(3)] units form sheets in the crystals, which are about 4 A apart and thus indicate pi stacking interactions.