Group 6 metal carbonyl complexes containing 3,5-dimethyl-4-ferrocenylmethylpyrazole: synthesis, structure and electrochemical properties

Abstract

Reaction of M(CO)₆ with 3,5-dimethyl-4-ferrocenylmethylpyrazole under UV irradiation yields monosubstituted group 6 metal carbonyl complexes M(CO)₅L (M = Cr, Mo or W; L = 3,5-dimethyl-4-ferrocenylmethylpyrazole). Their electrochemical behaviour, investigated by cyclic voltammetry, indicates that chromium and tungsten complexes exhibit two one-electron quasi-reversible couples corresponding to the ferrocenyl group and the chromium or tungsten centre, respectively, while the molybdenum complex has one quasi-reversible couple corresponding to the ferrocenyl group and one irreversible oxidation process for molybdenum. The crystal structure of W(CO)₅L, determined by X-ray diffraction methods, shows that ferrocenylpyrazole acts as a monodentate ligand, and W is six-coordinate with quasi-octahedral coordination geometry. The complex is linked into a one-dimensional chain in the lattice through weak intermolecular hydrogen bonds with metal carbonyls acting as acceptors.

Keywords:

• Group 6 carbonyl complexes
• Ferrocene
• Pyrazole
• Cyclic voltammetry
• Crystal structure

Acknowledgements

This work was supported by the National Natural Science Foundation of China (20421202), the Innovative Foundation for Undergraduates at Nankai University (R.Y.T.) and the Research Fund of Yibin University (X.X.G.).