Transition metal catalyzed Fe–C coupling reactions in synthesis of dicarbonyl(2-thienylethynyl)(η5-cyclopentadienyl)iron complex: Spectroscopic, structure and electrochemical study

The new σ-alkynyl iron(II) complex Cp(CO)2Fe-C≡C-(2-C4H3S) was synthesized with application of several known approaches based on the transition metal (Pd/Cu–, Au–, Cu– and Pd–) catalyzed Fe–C coupling reactions of 2-ethynylthiophene or 2-[(trimethylsilyl)ethynyl]thiophene with cyclopentadienyliron dicarbonyl iodide. The yield of the complex in these reactions was found to strongly depend on the catalyst used. The conditions, catalysts, and reagents that provide the highest yields of the desired 2-thienylethynyl iron complex were determined. The complex was characterized by IR, 1H and 13C NMR spectroscopy. The molecular structure of Cp(CO)2Fe–C≡C-(2-C4H3S) established by X-ray diffraction analysis exhibits a three-leg piano stool geometry. The redox properties of the new complex were studied.