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

The new tridentate ligand, SMeNHS = 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, [Fe32-SMeNS)4]­(OTf)2 (1) which is fully characterized by structural and spectroscopic methods. X-ray structural data reveal that 1 contains four SMeNS 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 1 includes a central, high-spin Fe­(II) (S = 2) with two low-spin (S = 0) peripheral Fe­(II) centers. Complex 1 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-SMeNS)­L2]2}­(OTf)2 (24). 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 1 in CH2Cl2 produces primarily the diamagnetic, mononuclear Fe­(II) complex, {Fe­(SMeNS)­[P­(OMe)3]3}­(OTf) (5).