Monomeric and dimeric anhydride-functionalized ferrocene: synthesis and structural analysis

A series of mono-substituted ferrocene-based anhydrides of the general formula FcCO2COAr (Fc = Fe(η5-C5H5)(η5-C5H4); Ar = Ph (1a), 4-Cl-C6H4 (1b), 4-CH3-C6H4 (1c)) were synthesized by acyl substitution of ferrocene carboxylic acid with the corresponding acid chlorides in the presence of triethylamine (Et3N) as a non-nucleophilic base. Furthermore, treatment of ferrocene carboxylic acid with bifunctional acid chlorides yielded dimeric anhydride-bridged ferrocene derivatives of the type [1,n- {Fe(η5-C5H5)(η5-C5H4-CO2CO}2-C6H4)] (n = 2 (2a), 3 (2b), 4 (2c)). Spectroscopic characterization was performed using Fourier-transform infrared (FT-IR) spectroscopy, proton and carbon-13 nuclear magnetic resonance spectroscopy, and ultraviolet-visible (UV-Vis) spectroscopy to confirm the structural integrity and electronic properties of the compounds. Single-crystal X-ray diffraction analyses were carried out for compounds 1a, 1b, 2a, 2b, and 2c, providing unambiguous structural elucidation and confirming the molecular connectivity and geometrical parameters of the mono- and dimeric ferrocene anhydride architectures.