Synthesis and Characterization of a Ditriflate-Bridged Diiron(II) Complex with Syn-N-Donor Ligands: Fe2(μ-OTf)2(PIC2DET)2(BARF)2

摘要

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, contains, [Fe2(μ-OTf)2(PIC2DET)2]²⁺ 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, 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 – 300K) to a spin-only isotropic exchange Hamiltonian H = −2JS₁·S₂ are consistent with weak antiferromagnetic coupling between the two iron atoms with J ~ −0.99(2) cm⁻¹ and g = 2.10(1).