Synthesis and magnetic characterization of a dinuclear complex of low-coordinate iron(II)

A dinuclear complex of three-coordinate iron(II), synthesized by a transamination reaction, displays weak superexchange between the anisotropic high-spin ions. [Display omitted] Low-coordinate ions possess exciting magnetic, optical, and reactive properties that may afford novel material physics. Hence, it is important to test both synthetic methods for realizing extended solids of such ions as well as the properties of smaller molecular fragments of envisioned future materials. Herein, we report the synthesis and characterization of a new dinuclear Fe species, [{(Me3Si2)2N}Fe{μ-p-{HN(SiMe3)}(C6Me4){N(SiMe3)}}2Fe{N(SiMe3)2}] (1), formed through a transamination reaction between [Fe{N(SiMe3)2}2]2 and the bulky diamine p-{HN(SiMe3)}2(C6Me4) (L). The Fe centers of this dimer assume a pseudo-trigonal-planar, three-coordinate conformation in 1, bridged by two aromatic diamines. Single-crystal X-ray diffraction, IR spectroscopy, and Mössbauer spectroscopy enable the assignment of both Fe centers as the 2+ oxidation state. Magnetic studies show that 1 displays a weak antiferromagnetic exchange interaction (J = −2.33 cm−1) and moderate zero-field splitting (D = 7.51 cm−1). Importantly, these studies demonstrate the viability of using transamination to bridge high-spin low-coordinate metal ions and hence the technique may, in the future, produce new extended structures.