Preparation, Crystal Structure and Properties of a Pentametallic 3‐Ferrocenyl‐2‐crotonic acid‐Bridged Copper (II) Complex

The synthesis and characterization of the copper (II) complex [Cu 2 (OOCCH = C(CH 3 )Fc) 3 (phen) 2 ]CIO 4 · 2H 2 O (1) are reported. The structure of the complex was determined by single‐crystal X‐ray analysis. The compound crystallizes in the monoclinic system, space group Pc , with Z =2, a = 1.2799(4) nm, b =0.9969 (4) nm, c = 2.5228 nm, and β = 91.576 (1) °. The cationic part of 1 indicates a penametallic core in which three 3‐ferrocenyl‐2‐crotonic acid salt (FCA) groups act as (O, O') bridging ligands between two copper (II) ions with a square‐pyramidal environment. Cyclic voltammetric experiments in acetonitrile have been performed mainly to examine the Fe(II) → Fe(III) one‐electron oxidation in FCA and its complex. The variable‐temperature magnetic susceptibility measurements revealed very weak intramolecular anti‐ferromagnetic coupling. Fitting parameters are 2 J = ‐0.2 cm −1 , g = 2.114, and θ = 0K.