Square‐pyramidal chalcogenide tungsten clusters with pyrazole

This work presents the synthesis of two novel pentanuclear tungsten chalcogenide complexes, namely [{W5Q5(μ-pz)4}(pzH)5]Cl2 (Q = S, Se). To obtain [{W5S5(μ-pz)4}(pzH)5]Cl2, W6Cl12 was reacted with Na2S, S, and pyrazole in a sealed glass ampoule. The synthesis of [{W5Se5(μ-pz)4}(pzH)5]Cl2 was conducted in two stages. The structure of the sulfide cluster complex was elucidated through single-crystal X-ray diffraction analysis. Furthermore, both compounds were characterized by NMR spectroscopy and mass-spectrometry, and their redox properties were investigated by cyclic voltammetry. Both compounds exhibit two consecutive reversible or quasi-reversible one-electron reductions, corresponding to the transition from the 14 VEC to 15 VEC and 16 VEC forms, respectively.