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Oxalato-bridged dinuclear complexes of Cr(III) and Fe(III): Synthesis, structure, and magnetism of [(C2H5)4N]4[MM'(ox)(NCS)8] with MM' = CrCr, FeFe, and CrFe

Abstract : A new series of homo- and heterometallic oxalato-bridged dinuclear compounds of formulas [Et4N]4[MM'(ox)(NCS)8] ([Et4N]+ = [(C2H5)4N]+; ox = C2O42-) with MM' = Cr(III)-Cr(III) (1), Fe(III)-Fe(III) (2), and Cr(III)-Fe(III) (3) is reported. They have been structurally characterized by infrared spectra and single-crystal X-ray diffraction. The three compounds are isostructural and crystallize in the orthorhombic space group Cmca with Z = 8, a = 16.561(8) Å, b = 13.481(7) Å, and c = 28.168(8) Å for 1, a = 16.515(2) Å, b = 13.531(1) Å, and c = 28.289(4) Å for 2, a = 16.664(7) Å, b = 13.575(6) Å, and c = 28.386(8) Å for 3. The structure of 3 is made up of a discrete dinuclear anion [CrFe(ox)(NCS)8]4- and four disordered [Et4N]+ cations, each of them located on special positions. The anion, in a crystallographically imposed C(2h) symmetry, contains metal cations in distorted octahedral sites. The Cr(ox)Fe group, which is planar within 0.02 Å, presents an intramolecular metal-metal distance of 5.43 Å. Magnetic susceptibility measurements indicate antiferromagnetic pairwise interactions for 1 and 2 with J = -3.23 and -3.84 cm-1, respectively, and ferromagnetic Cr-Fe coupling with J = 1.10 cm-1 for 3 (J being the parameter of the exchange Hamiltonian H = -2JS1S2). The ESR spectra at different temperatures confirm the magnetic susceptibility data.
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Submitted on : Thursday, April 19, 2018 - 2:49:17 PM
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Smail Triki, F. Bérézovsky, J. Sala Pala, E. Coronado, C.J. Gómez-Garcí, et al.. Oxalato-bridged dinuclear complexes of Cr(III) and Fe(III): Synthesis, structure, and magnetism of [(C2H5)4N]4[MM'(ox)(NCS)8] with MM' = CrCr, FeFe, and CrFe. Inorganic Chemistry, American Chemical Society, 2000, 39, pp.3771--3776. ⟨10.1021/ic990439w⟩. ⟨hal-01771382⟩

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