Heterometallic complexes combining [MnIII(salpn)]+ and [Fe(CN)6]4− units as the products of reactions between [MnIII(salpn)(H2O)C(CN)3] and [Fe(CN)6]3−/4−

Abstract

The reaction of [Fe(III)(CN)₆]³⁻ with neutral [Mn(salpn)(H₂O)C(CN)₃] (salpn: N,N′-propylenebis(salicylideneiminato)) (1) produces two new heterometallic complexes [{Mn^III(salpn)(H₂O)}₂{Mn^III(salpn)(H₂O)_0.7(CH₃OH)_0.3}₂Fe^II(CN)₆]·n(H₂O/CH₃OH) (2) and [{Mn^III(salpn)}₄{Mn^III(salpn)(H₂O)}₂Fe^II(CN)₆]{C(CN)₃}₂·4H₂O (3), which are characterized by single-crystal X-ray diffraction. In this reaction, the [C(CN)₃]⁻ ligand reduces Fe(III) to Fe(II). Complex 3 can be prepared directly using hexacyanoferrate(II). One more complex containing the hexacyanoferrate(II), [{Mn^III(salpn)(CH₃OH)_0.67(H₂O)_0.33}₆Fe^II(CN)₆]{ClO₄}₂·8H₂O (4), is obtained in the reaction of [Fe(II)(CN)₆]⁴⁻ with the cationic complex [Mn₂(salpn)₂(H₂O)₂](ClO₄)₂. The iron(II) centers in the complexes 2 and 4 are linked via cyano-bridges with the four and six [Mn^III(salpn)]⁺ fragments, respectively. The structure of 3 consists of the cyano-bridged [Mn^III₆Fe^II] repeating units linked by double phenolate bridges into a one-dimensional polymeric chain. The magnetic properties of 3 indicate a ferromagnetic coupling between Mn^III centers in the double phenolate-bridged [Mn^III(salpn)]₂ dinuclear subunits. Quantum calculations within the Heisenberg–Van Vleck model are performed giving the exchange constant J = 0.64 cm⁻¹ and the zero-field splitting parameter D = −3.5 ± 0.5 cm⁻¹. The ac-susceptibility obeys the Arrhenius law with the activation energy E_a = 11.89 cm⁻¹.