Mono- and hexanuclear zinc halide complexes with soft thiopyridazine based scorpionate ligands

Abstract

Scorpionate ligands with three soft sulfur donor sites have become very important in coordination chemistry. Despite its ability to form highly electrophilic species, electron-deficient thiopyridazines have rarely been used, whereas the chemistry of electron-rich thioheterocycles has been explored rather intensively. Here, the unusual chemical behavior of a thiopyridazine (6-tert-butylpyridazine-3-thione, H tBu Pn) based scorpionate ligand towards zinc is reported. Thus, the reaction of zinc halides with tris(6-tert-butyl-3-thiopyridazinyl)borate Na[Tn tBu ] leads to the formation of discrete torus-shaped hexameric zinc complexes [Tn tBu ZnX] 6 (X = Br, I) with uncommonly long zinc halide bonds. In contrast, reaction of the sterically more demanding ligand K[Tn Me,tBu ] leads to decomposition, forming Zn(HPn Me,tBu ) 2 X 2 (X = Br, I). The latter can be prepared independently by reaction of the respective zinc halides and two equiv of HPn Me,tBu . The bromide compound was used as precursor which further reacts with K[Tn Me,tBu ] forming the mononuclear complex [Tn Me,tBu ]ZnBr(HPn Me,tBu ). The molecular structures of all compounds were elucidated by single-crystal X-ray diffraction analysis. Characterization in solution was performed by means of 1 H, 13 C and DOSY NMR spectroscopy which revealed the hexameric constitution of [Tn tBu ZnBr] 6 to be predominant. In contrast, [Tn Me,tBu ]ZnBr(HPn Me,tBu ) was found to be dynamic in solution.