Syntheses and structures of nickel(II) and copper(II) complexes with a 14-membered tetraaza macrocyclic ligand

Abstract

Nickel(II) and copper(II) complexes of 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0 7.12]docosane ( L) were prepared, isolated and characterized as trans-[Ni(CH 3CN) 2( L)][PF 6] 2 ( 1) and trans-[Cu(CH 3CN) 2( L)][PF 6] 2 ( 2) by UV–Vis, IR and X-ray crystallography. In complex 1 the coordination geometry about the nickel atom is close to octahedral with four equatorial nitrogen atoms from the macrocycle and two axial nitrogen atoms from acetonitrile. The solid-state electronic spectrum of 1 using the diffuse reflectance method shows a characteristic high-spin d 8 nickel(II) ion in a distorted octahedral environment. However, the spectrum of 1 dissolved in acetonitrile indicates that the square-planar species is predominant over the octahedral species. The copper ion environment in 2 is similar to that of nickel complex 1, but the great tetragonal distortion in 2 is observed with much longer Cu–N (acetonitrile) distances than Ni–N (acetonitrile) distances in 1. The electronic spectrum of square-planar [Cu( L)][PF 6] 2 in acetonitrile or the spectrum of 2 dissolved in acetonitrile in the visible region is basically similar to that of the Nujol mull solid-state diffuse reflectance spectrum of 2, indicating that the square-planar [Cu( L)][PF 6] 2 coordinates to acetonitrile molecules to form 2.