Arene σ,π complexes: synthesis and electrochemistry of (η6-1,4-C6H4XFp)Cr(CO)3 (where X = H, Me, Cl, or OMe; Fp = (η5-C5H5)Fe(CO)2)

Abstract

The bimetallic complexes (η6-1,4-C6H4XFp)Cr(CO)3 (where X = H, Me, Cl, or OMe; Fp = (η5-C5H5)Fe(CO)2) were synthesized in 32–80% yields by the reaction of NaFp with (η6-1,4-C6H4XF)Cr(CO)3 (where X = H, Me, or OMe) or (η6-1,4-C6H4Cl2)Cr(CO)3. They were fully characterized by conventional spectroscopic techniques. In these complexes, the arenes are σ bound to the Fp group and π bound to the Cr(CO)3 group. The 13C NMR data suggest that a synergic substituent–arene–Fp π interaction is occurring. Cyclic voltammetric studies of these complexes in CH2Cl2 show that they are oxidized reversibly to give stable radical cations, and confirm that the Fp substituents are strong net electron donors to the Cr(CO)3 fragments. Keywords: bimetallic, iron, chromium, arene, oxidation.