Synthesis of cyclopentadienyl iron complexes with substituted phenylene ligands via Suzuki coupling

Abstract

Cationic cyclopentadienyl iron complexes of substituted phenylenes [CpFe(p-CH3-C6H4-Ar)]PF6 and [CpFe(p-Ar-C6H4-Ar)]PF6 were obtained in 37–73% yields by Pd-catalyzed Suzuki coupling reactions of [CpFe(p-CH3-C6H4-Cl)]PF6 and [CpFe(p-Cl-C6H4-Cl)]PF6 with polyarylboronic acids Ar-B(OH)2 (Ar = biphenyl, naphthyl, phenanthryl, bithienyl). The complex [CpFe(p-CH3-C6H4-Cl)]PF6 also underwent Sonogashira-type coupling with phenylacetylene to give the compound [CpFe(p-CH3-C6H4-CC-Ph]PF6 in 26% yield. Such coupling reactions represent an alternative approach to [CpFe(arene)]PF6 complexes, which are typically obtained from ferrocene via Bolesova-Nesmeyanov reaction under harsh conditions (AlCl3, >100 °C). The structures of the products of Suzuki reaction were established by single-crystal X-ray diffraction analysis.