Organometallated Halonium Salts of the Type [{Cp(CO) 2 Fe} 2 X]SbY 6 (X = Cl, Br, I; Y = F, Cl)

The reaction of CpFe(CO) 2 X (X = Cl, Br, I) with SbY 5 (Y = F, Cl) in toluene leads to the cationic, halogen‐bridged compounds [{Cp(CO) 2 Fe} 2 X]SbY 6 ( 1 – 6 ). The halide of CpFe(CO) 2 X is eliminated by the Lewis acid SbY 5 , and the fragment “CpFe(CO) 2 + ” reacts with further CpFe(CO) 2 X to form the halogen bridge between both the organometallic substituents. The exclusive formation of the counter anion SbY 6 – is caused by the oxidizing action of the antimony pentahalides, by which SbY 3 and the interhalogens XY are always obtained. The compounds have been characterized by their NMR‐, IR‐ and Mass spectra, the compounds 1 – 3 and 6 additionally by single crystal structure analyses. They show decreasing bond angles Fe–X–Fe following the range Cl → Br → I and the VSEPR concept; the two CpFe(CO) 2 groups are staggered with the dihedral angle Cp(centre)–Fe–Fe–Cp(centre) of about 160°.