Synthesis, structure and properties of heterotrinuclear carboxylate complexes [Fe2M(Ca, Sr, Ba)O(CCl3COO)6(THF)n]

Three novel μ3-oxo trinuclear carboxylates [Fe2CaO(CCl3COO)6(THF)4] · THF (1), [Fe2SrO(CCl3COO)6(THF)6] · 0.5H2O · 0.5THF (2) and [Fe2BaO(CCl3COO)6(THF)6] · 0.5H2O · 0.5THF (3) have been synthesised and subsequently characterised by X-ray structure analysis, thermal gravimetry (TG), infra red (IR) spectroscopy and magnetic measurements. Compounds 1 and 3 are molecular complexes with s- and d-metals displayed in the apexes of isosceles triangles with a triply bridging oxygen atom at its centre. The Ca⋯Fe and Ba⋯Fe separations have the values 3.750(1) and 4.177(1) Å, respectively. In comparison with these, Fe⋯Fe separations, 3.229(2) Å in 1 and 3.201(1) Å in 3, appear much shorter. The molecular complexes obey C2 symmetry with the twofold axis passing through s metal and μ3-oxo atom. The coordination numbers are 6, 7 and 9 for iron, calcium and barium correspondingly.Magnetic studies reveal the presence of an antiferromagnetic exchange in the isosceles triangular skeletons of the trinuclear species. Using the spin Hamiltonian H = −2J12[S1S2], the fitting parameters gFe = 2.00, JFe–Fe = −58.90 cm−1 for 1 and −60.40 cm−1 for 3; gFe = 2.14, JFe–Fe = −75.40 cm−1 for 2 have been estimated.

Graphical abstractThree novel μ3-oxo trinuclear carboxylates [Fe2CaO(CCl3COO)6(THF)4] · THF (1), [Fe2SrO(CCl3COO)6(THF)6] · 0.5H2O · 0.5THF (2) and [Fe2BaO(CCl3COO)6(THF)6] · 0.5H2O · 0.5THF (3) have been synthesised and characterised by X-ray structure analysis, TG-, IR-spectroscopy and magnetochemistry. Compounds 1 and 3 are molecular complexes with s- and d-metals displayed in the apices of isosceles triangles with a triply bridging oxygen atom at its centre.Figure optionsDownload full-size imageDownload as PowerPoint slide