Optically active transition metal compounds, chiral at the metal center. Synthesis and stereochemical studies of the chiral cyclopentadienyl iron complexes [Fe(h5-C5H5){(S)-Prolophos}(CO)PF6

The reaction between [Fe(η5-C5H5)(CO)2Cl] and {(S)-Prolophos}, a chiral chelating ligand without a C2 axis, yields [Fe(η5-C5H5){(S)-Prolophos}(CO)]Cl spontaneously and quantitatively; the chelation of the ligand forms a pair of diastereoisomers differing only in the iron configuration. Reprecipitation with NH4PF6 leads to [Fe(η5-C5H5){(S)-Prolophos}(CO)]PF6 with 83% diastereoisomeric excess (d.e. %) at the iron chiral centre. One recrystallization is sufficient to give the optically pure iron complex whose absolute configuration has been tentatively assigned as S. [Fe(η5-C5H5){(S)-Prolophos}(CO)]PF6 on UV irradiation in THF splits off the CO ligand to give the highly reactive complex [Fe(η5-C5H5){(S)-Prolophos}(THF)]PF6; the iron(tetrahydrofuran) complex regenerates the title compound with an overall retention of configuration upon treatment with carbon monoxide.