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

Abstract

The preparation of a series of mononuclear complexes [ML2]Xn{M = FeII, CoIII, CoII, or NiII; 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 D2d symmetry) structure is assigned to all the complexes on the evidence of i.r., electronic, and Mossbauer 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.