Mononuclear, Dinuclear, and Trinuclear Iron Complexes Featuring a New Monoanionic SNS Thiolate Ligand

The new tridentate ligand, S^<i>Me</i>N^<i>H</i>S = 2-(2-methylthiophenyl)­benzothiazolidine, prepared in a single step from commercial precursors in excellent yield, undergoes ring-opening on treatment with Fe­(OTf)₂ in the presence of base affording a trinuclear iron complex, [Fe₃(μ₂-S^<i>Me</i>NS^–)₄]­(OTf)₂ (<b>1</b>) which is fully characterized by structural and spectroscopic methods. X-ray structural data reveal that <b>1</b> contains four S^<i>Me</i>NS^– ligands meridionally bound to two pseudooctahedral iron centers each bridged by two thiolates to a distorted tetrahedral central iron. The combined spectroscopic (UV–vis, Mössbauer, NMR), magnetic (solution and solid state), and computational (DFT) studies indicate that <b>1</b> includes a central, high-spin Fe­(II) (<i>S</i> = 2) with two low-spin (<i>S</i> = 0) peripheral Fe­(II) centers. Complex <b>1</b> reacts with excess PMePh₂, CNxylyl (2,6-dimethylphenyl isocyanide), and P­(OMe)₃ in CH₃CN to form diamagnetic, thiolate-bridged, dinuclear Fe­(II) complexes {[Fe­(μ-S^<i>Me</i>NS^–)­L₂]₂}­(OTf)₂ (<b>2</b>–<b>4</b>). These complexes are characterized by elemental analysis; ¹H NMR, IR, UV–vis, and Mössbauer spectroscopy; and single crystal X-ray diffraction. Interestingly, addition of excess P­(OMe)₃ to complex <b>1</b> in CH₂Cl₂ produces primarily the diamagnetic, mononuclear Fe­(II) complex, {Fe­(S^<i>Me</i>NS^–)­[P­(OMe)₃]₃}­(OTf) (<b>5</b>)