PPEPO)(C6H5COO)(2)(CH3COOH)]CLO4-CENTER-DOT-C4H10O - SYNTHESIS AND CHARACTERIZATION OF AN ASYMMETRIC DINUCLEAR NICKEL(II) COMPLEX SHOWING UNUSUAL COORDINATION BEHAVIOR WITH RELEVANCE TO THE ACTIVE-SITE OF UREASE

The synthesis of the novel asymmetric ligand yl)amino]-3-[2-(2-pyridyl )ethoxy]-2-hydroxypropane (ppepOH) is reported. The ligand is suitable to form asymmetric dinuclear complexes with various transition metal ions. As an example, the synthesis and X-ray structure analysis of the dinickel(II) complex [Ni-2(ppepO)(C6H5COO)(2)(CH3COOH)]ClO4 . C(4)H10 O are described. The complex crystallizes in the monoclinic space grou p P2(1)/n with the following unit cell parameters: a = 13.704(10) Angs trom, b = 14.849(10) Angstrom, c = 22.697(14) Angstrom, beta = 96.80(5 )degrees, Z = 4. The nickel(II) ions are bridged by the alkoxy donor o f the ligand and two benzoate anions. The hexadentate ligand leaves a free coordination site at one of the nickel(II) ions, which is occupie d by a monodentate coordinated acetic acid molecule. The coordination of the neutral acetic acid molecule is selectively stabilized by a str ong intramolecular hydrogen bond of the acidic proton to the mu-alkoxo bridge of the dinuclear complex. The asymmetric complex was prepared in order to mimic the substrate uptake in the dinuclear active site of ureases. The magnetic and spectroscopic properties of the complex wer e determined and related to those of the urease enzymes.