INTERACTION OF TRANSITION-METAL AND POST-TRANSITION-METAL IONS WITH O2N2-DONOR MACROCYCLES INCORPORATING PENDANT PYRIDYLMETHYL GROUPS

The interaction of cobalt(II), nickel(II), copper(II), zinc(II) and ca dmium(II) with pyridylmethyl pendant-arm derivatives of O2N2-donor mac rocycles incorporating from 14- to 17-membered rings has been investig ated. Thermodynamic stabilities of the 1:1 (metal:ligand) complexes ha ve been determined in 95% methanol (I = 0.1 mol dm(-3), NEt(4)ClO(4); 25 degrees C). The data indicate that the pyridyl nitrogens participat e in co-ordination to the respective metals in each complex in solutio n. The crystal structures of the nickel(II) and copper(II) complexes o f the 15-membered O2N2-donor macrocycle containing two pendant 2-pyrid ylmethyl groups have also been determined. For the nickel complex only the nitrogens of the macrocyclic ring and the pendant pyridyl nitroge ns are co-ordinated; overall, the co-ordination geometry is distorted octahedral, with the fifth and sixth positions being occupied by a bid entate nitrate group. In contrast, in the copper complex the four nitr ogens and at least one of the two ring ether oxygens are co-ordinated (there is a long contact with the second); these two oxygens may be co nsidered to displace those of the nitrate chelate found in the nickel complex. In the nickel complex, Ni-N are 2.119(6), 2.113(4) (aliphatic ), 2.061(4). 2.032(5) (aromatic) and Ni-O 2.137(5), 2.230(4) Angstrom. in the copper complex, CU-N are 2.06(1). 2.02(1) (aliphatic). 1.97(1) , 2.04(1) (aromatic) and Cu-O 2.319(9). 2.92(1) Angstrom. The N(alipha tic)-M-N (aromatic) angles, trans within the ligand, are 111.4(2), 177 .2(2) (M = Ni) and 127.6(4), 179.1(5)degrees (M = Cu).