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

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journal contribution
posted on 27.06.2017, 17:27 by Michael Tüchler, Stefan Holler, Jörg A. Schachner, Ferdinand Belaj, Nadia C. Mösch-Zanetti
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(RPnS3PnR)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(RPnS3PnR)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 RPnS3PnR ligands and by two sulfur atoms of the central atom in the S3 unit. The diamagnetic complexes exhibit unusually high redox potentials for the Fe2+/3+ couple at E1/2 = 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.