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

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, Pb-2(L2)(ClO4)(2) 1, in acetonitrile with two equivalents of CoCl2.6H(2)O leads to the isolation of an orange, six-coordinate complex, [Co-2(II)(L2)(OH2)(3)(NCCH3)](ClO4)(2).H2O.2CH(3)CN 2. Subsequent reaction of 2 with two equivalents of NaOCN or NEt4Cl yielded red-purple five-coordinate [Co-2(II)(L2)(NCO)(2)] 3 and red five-coordinate [Co-2(II)(L2)(Cl)(2)].1.5CH(3)CN 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.