Ammonium and Phosphonium Salts Containing Monoanionic Iron(II) Half-Sandwich Complexes [Fe(η5-Cp*)X2]- (X = Cl - I)

Half-sandwich iron(II) dihalido complexes of the type [Fe(eta(5)-Cp')X-2](-) (Cp' = C5H5 or substituted cyclopentadienyl) which are thermally stable at room temperature are extremely scarce, being limited to congeners containing the bulky C5H2-1,2,4-tBu(3) ligand. We extended this to homologues [Fe(eta(5)-Cp*)X-2](-) (X = Cl, Br, I) containing the particularly popular C5Me5 (Cp*) ligand. Corresponding ionic compounds ER4[Fe(eta(5)-Cp*)X-2] are easily accessible from FeX2, MCp* (M = Li, K) and a suitable halide source R4EX (E = N, P) in THF. Despite their high sensitivity towards air and moisture, the new compounds NnPr(4)[Fe(eta(5)-Cp*)X-2] (X = Cl, Br), NnPr(4)[Fe(eta(5)-Cp*)BrCl], and PPh4[Fe(eta(5)-Cp*)X-2] (X = Cl, Br, I) were structurally characterised using single-crystal X-ray diffraction. NnPr(4)[Fe(eta(5)-Cp*)Cl-2] reacts readily with CO to afford [Fe(eta(5)-Cp*)Cl(CO)(2)], indicating the synthetic potential of ER4[Fe(eta(5)-Cp*)X-2] in FeCp* half-sandwich chemistry.

Automated summary

This study reports the synthesis and structural characterization of novel half-sandwich iron (II) dihalido complexes that exhibit high thermal stability. The compounds were successfully synthesized and their structures were determined using single-crystal X-ray diffraction. Further investigation revealed the synthetic potential of these compounds in FeCp* half-sandwich chemistry.