Unusual C–N Coupling Reactivity of Thiopyridazines: Efficient Synthesis of Iron Diorganotrisulfide Complexes

The reaction of iron­(II) triflate with 6-tert-butyl-3-thiopyridazine (PnH) and 4-methyl-6-tert-butyl-3-thiopyridazine (^MePnH) respectively led to iron bis­(diorganotrisulfide) complexes [Fe­(^RPnS₃Pn^R)₂]­(OTf)₂ [R = H (1a) and Me (2a)]. The corresponding perchlorate complexes were prepared by using the iron­(II) chloride precursor and the subsequent addition of 2 equiv of NaClO₄, giving [Fe­(^RPnS₃Pn^R)₂]­(ClO₄)₂ [R = H (1b) and Me (2b)]. The compounds were fully characterized including single-crystal X-ray diffraction analysis. All four compounds exhibit nearly perfect octahedral geometries with an iron center coordinated by four nitrogen atoms from two ^RPnS₃Pn^R ligands and by two sulfur atoms of the central atom in the S₃ unit. The diamagnetic complexes exhibit unusually high redox potentials for the Fe^2+/3+ couple at E_1/2 = 1.15 V (for 1a and 1b) and 1.08 V (for 2a and 2b) versus Fc/Fc⁺, respectively, as determined by cyclic voltammetry. Furthermore, the source of the extra sulfur atom within the S₃ unit was elucidated by isolation of C–N-coupled pyridazinylthiopyridazine products.