Mononuclear iron, cobalt, and nickel complexes of a 30-membered macrocyclic ligand

Abstract

The preparation of a series of mononuclear complexes [ML²]X_n{M = Fe^II, Co^III, Co^II, or Ni^II; L²= a 30-membered, potentially decadentate, macrocyclic Schiff base ligand; X =[ClO₄]^–, [BPh₄]^–, or [Co(NCS)₄]^2–, n= 1, 2, or 3} from the binuclear complex [Pb₂L²(SCN)₄] is described. Unlike the reactant lead(II) complex, in which the macrocycle uses all ten donor atoms in bonding to the metal ions, only the six nitrogen atoms are co-ordinated in the new complexes. A distorted octahedral (approximate D_2d symmetry) structure is assigned to all the complexes on the evidence of i.r., electronic, and Mössbauer spectra, magnetic data, and of the properties of corresponding complexes of two open-chain Schiff-base ligands. The d⁶ and d⁷ complexes have spin-singlet and spin-doublet ground states, respectively. The electrochemical behaviour of the iron and cobalt complexes is reported and correlated with other properties.