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

Abstract

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)](OTf) [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)](ClO) [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.

Mono- and Hexanuclear Zinc Halide Complexes with Soft Thiopyridazine Based Scorpionate Ligands

“…Furthermore, the pyridazine based scorpionate ligands exhibit photochemical reactivity, as observed with potassium hydrotris(6-tert-butyl-3-thiopyridazinyl)borate K[Tn tBu ] which is, upon exposure to light, transformed into 2 equiv of 6-tert-butylpyridazine-3-thione and 1 equiv of 4,5-dihydro-6-tert-butylpyridazine-3-thione [12]. The parent 6-tert-butylpyridazine-3-thione is redox-active in presence of iron(II) under formation of di-organotrisulfide based iron complexes and concomitant C-N-coupled, desulfurized pyridazinyl-thiopyridazines [13]. The iron compounds exhibit unusually high redox potentials due to the electron-deficiency of the pyridazine heterocycle.…”

Cooperative Interactions in the Second Coordination Sphere of Pyridazine/Pyridine Containing Polyazaheterocyclic Iron(II) Complexes Favor Protonation

“…However, for first row transition metals, this generally requires that the pyridazine is part of a larger ligand scaffold or macrocycle functionalized with additional pendant donor sites. In the absence of this cooperation and notably in higher valent metals, pyridazines typically coordinate in a monodentate fashion through a single nitrogen . This is likely due to the initial coordination with the first nitrogen decreasing the basicity of remaining site for interaction with an additional metal.…”

Synthesis and Characterization of a Thiopyridazinylmethane-Based Scorpionate Ligand: Formation of Zinc Complexes and Rearrangement Reaction

“…In our group we focus on the synthesis and reactivity of thiopyridazine-based scorpionate ligands. ,,− They show interesting reactivity contrasting with that of other soft scorpionates, as they were found to be photoreactive and prone to the formation of boratrane complexes with the concomitant reduction of the metal center. ,,, This led us to investigate the formation of a carbon-based scorpionate with this heterocycle. The tert -butyl group of the used thiopyridazine might influence the steric hindrance of the formed complexes, while the additional nitrogen atom in the heterocycle might alter the electron-donating properties of the ligand in comparison to its thiopyridine-based analogue.…”