The copper(II) and nickel(II) complexes of three new 1,2-bis(1,4,7- triazacyclononane) ligands containing unsaturated four carbon bridging groups is studied by continuous variation UV-Vis spectroscopic and pH potentiometric equilibrium experiments. The cis-butene-2 (LC) linked ligand may form monomeric MN6-type complexes while the trans-butene-2 (LT) and butyne-2 (LY) ligands are prevented by their stereochemistry from forming monomeric complexes and form oligomeric complexes. It is determined that the stability of the CuLC2+complex is not appreciably different from the oligomeric complexes of LTand LY. Single-crystal X-ray structure determinations are made on three square pyramidal Cu2L4+complexes: [Cu2LCCl4] (1), [Cu2LYCl4] (2), and [Cu2LT(NO3)2(H2O)2](NO3)2(3). The structure of [Ni2(LC)2](ClO4)4·2H2O (4) is a binuclear dimer that contains two nickel(II) ions sandwiched between two ligands, indicating that bis(aneN3) ligands with four linker atom chains may form either monomeric or oligomeric structures. © 2003 Elsevier B.V. All rights reserved.
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