SYNTHESIS AND PROPERTIES OF NICKEL(III) COMPLEXES OF HEXAAZAMACROCYCLIC LIGANDS

The six-coordinate Ni(III) macrocyclic complexes [Ni-III(L)X-2](+) whe re L is droxyethyl)-1,3,6,8,10,13-hexaazacyclotetra-decane (1), -cyano ethyl)-1,3,6,8,10,13-hexaazacyclotetradecane (2) or 1,8-dimethyl-1,3,6 ,8,10,13-hexaazacyclotetradecane (3) and X is Cl-, Br- or NO3- have be en prepared by the oxidation of the square-planar Ni(II) complexes of the corresponding macrocyclic ligands with (NH4)(2)S2O8, HNO3 or FeCl3 . 6H(2)O in H2O or MeCN. Although the ligands 1 and 2 contain pendant -arms with potentially coordinating groups, the NI(III) species are st abilized by the extra axial ligands. The six-coordinate Ni(III) comple xes show anisotropic axial EPR powder spectra with g(perpendicular to) values being greater than g(\) values and the magnetic moments rangin g from 1.88 to 2.29 BM, which indicate that the Ni(III) ions are in a low-spin d(7) state with the unpaired electron residing in the d(z)2 o rbital to adopt the tetragonally distorted octahedral geometry. (C) 19 98 Elsevier Science S.A.