Dicobalt(ii) complexes of a triazolate-containing Schiff-base macrocycle: synthesis, structure and magnetism

Abstract

A new Schiff-base macrocycle is obtained by the lead(II) ion templated [2+2] condensation of 3,5-diacetyl-1H-1,2,4-triazole and 1,4-diaminobutane in the presence of sodium hydroxide. Transmetallation of the resulting dilead complex, Pb₂(L2)(ClO₄)₂1, in acetonitrile with two equivalents of CoCl₂·6H₂O leads to the isolation of an orange, six-coordinate complex, [Co^II₂(L2)(OH₂)₃(NCCH₃)](ClO₄)₂·H₂O·2CH₃CN 2. Subsequent reaction of 2 with two equivalents of NaOCN or NEt₄Cl yielded red–purple five-coordinate [Co^II₂(L2)(NCO)₂] 3 and red five-coordinate [Co^II₂(L2)(Cl)₂]·1.5CH₃CN 4, respectively. In all three air-stable dicobalt complexes the macrocycles contain two high-spin cobalt(II) centers which are weakly antiferromagnetically coupled (2J = −3.0, −0.4, −3.5 cm⁻¹ for 2, 3 and 4, respectively). Complexes 2–4 have been characterized by X-ray diffraction and are the first structurally characterised complexes of a triazolate-containing macrocycle to date.