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 (PnH) respectively led to iron bis(diorganotrisulfide) complexes Fe(PnSPn) [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 NaClO, giving Fe(PnSPn) [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 PnSPn ligands and by two sulfur atoms of the central atom in the S unit. The diamagnetic complexes exhibit unusually high redox potentials for the Fe couple at E = 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 S unit was elucidated by isolation of C-N-coupled pyridazinylthiopyridazine products.