Synthesis and characterization of a ditriflate-bridged, diiron(II) complex with syn-N-donor ligands: [Fe2(μ-OTf)2(PIC2DET)2](BARF)2

The synthesis and characterization of the diiron(II) complex [Fe2(μ-OTf)2(PIC2DET)2](BARF)2 (2), where PIC2DET is a 2,3-diethynyltriptycene-linked dipicolinic methyl ester ligand, are described. The dication in 2, [Fe2(μ-OTf)2(PIC2DET)2]2+, contains two symmetry-equivalent iron atoms with octahedral coordination geometries. Each metal ion has a N2O4 atom donor set that includes four atoms from two picolinic ester N, O chelate rings, as well as two oxygen atoms from the bridging trifluoromethanesulfonate groups. The {Fe2(μ-OTf)2} core of 2 is stabilized by two PIC2DET ligands that bind the two metal ions in a head-to-head fashion, leading to an Fe⋯Fe distance of 5.173(1) Å. Molar conductivity data for 2 are consistent with [Fe2(μ-OTf)2(PIC2DET)2]2+ retaining its identity in acetone solutions, where it behaves as a 2:1 electrolyte. 1H NMR spectroscopic, and solution (d6-acetone) and solid-state magnetic susceptibility, data all indicate that the iron atoms of 2 are high-spin (S = 2). A fit of the magnetic data (2–300 K) to a spin-only isotropic exchange Hamiltonian H = −2JS1·S2 is consistent with weak antiferromagnetic coupling between the two iron atoms with J ∼ −0.99(2) cm−1 and g = 2.10(1).