Synthesis, crystal structure and electrochemical proerties of carbonylchromium and tungsten complexes containing substituted pyrazole ligands

摘要

A series of carbonylchromium and tungsten complexes containing substituted pyrazole ligands, M(CO)_5L, have been synthesized by the photochemical reactions of substituted pyrazoles with M(CO)_6 (M = Cr or W) . Their electrochemical behavior, investigated by cyclic voltammetry, indicates that the chromium complexes exhibit one reversible or quasi-reversible couple corresponding to a one-electron oxidation, whereas the tungsten complexes have one irreversible oxidation process. The crystal structure of W(CO)_5L [L = 3(5)-t-butylpyrazole] was determined by X-ray diffraction, indicating that 3(5)-t-butylpyrazole is a monodentate ligand, and that the central metal is six-coordinate with a quasi-octahedral coordination geometry. All new compouds were characterized by elemental analyses, i.r., ~1H-n.m.r. and by ~(13)C-n.m.r. in the case of the tungsten complexes.