Cyclic voltammetry of arylferrocenes and ferroceneanalogues of chalcones. substituent effects on theelectron density distribution in ferrocene derivatives

Abstract

Cyclic voltammetry studies of arylferrocenes and two series of ferrocene analogues of chalcone arepresented. Good correlations of the oxidation potentials (E1/2) with the (ζp )Hammett constants as well as with the 13C chemical shifts for carbon atoms with different positions in the ferrocenyl moiety have been found. The different sensitivities of these series to the substituent effects is discussed. The variation of the electron density distribution at the carbon atoms of the cyclopentadienyl rings is given numerically as a function of the electron- donating or electron withdrawing strengths of the substituents,Their anodic behavior was studied by cyclic voltammetry at a Pt électrode in aprotic solvent. Ail synthesized ferrocenes exhibited a one-electron réversible oxidation leading to the corre-sponding ferricinium cation. At low potential scan, the irréversible oxidation of the previous compounds.

The advantageous properties of the Cp * ligand - intensified electron donation, steric bulk, and enhanced solubility in comparison to the ubiquitous Cp ligand - are finding increasing use in organometallic chemistry. A systematic evaluation of synthetic routes to pentamethyl ferrocene compounds with a wide range of functionalities, including carboxyl, carbonyl, aminomethyl, vinyl, ethynyl, fulvenyl, cyclopentadienylmethyl, and others is reported. Spectroscopic, structural, and electrochemical properties of such functionalized pentamethylferrocenes Fc */2-R are compared to those of non-methylated ferrocenes Fc-R.