Synthesis, characterization and solution studies on heteronuclear iron–copper clusters containing diphosphine ligands: crystal structure of the dicluster [{Fe2(μ-CO)(CO)6(μ-PPh2)Cu}2(dppp)]

Treatment of dichloromethane solutions of the di-iron compound [NEt4][Fe2(CO)6(μ-CO)(μ-PPh2)] with one equivalent of [Cu(NCCH3)4]BF4 at low temperatures, followed by the addition of half of an equivalent of diphosphine ligand (diphosphine=bis(diphenylphosphino)methane (dppm), bis(diphenylphosphino)isopropane (dppip), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp) and 1,4-bis(diphenylphosphino)butane), produces high yields of the mixed-metal dicluster compounds [{Fe2(μ-CO)(CO)6(μ-PPh2)Cu}2(diphosphine)]. The molecular structure of the dppp derivative has been determined by X-ray crystallography. For a 1:1:1 molar ratio of the reagents, complex mixtures have been obtained and studied by variable-temperature 31P-NMR spectroscopy.