Optisch aktive Übergangsmetall-Komplexe, LXIII [1] Asymmetrische Induktion in C5H5Mo(CO)2LX-Diastereomeren-Gleichgewichten / Optically Active Transition Metal Complexes, LXIII [1] Asymmetrie Induction in C5H5Mo(CO)2LX Diastereoisomer Equilibria

Abstract

Abstract The thioamidato complexes C5H5(CO)2MoSC(R)NCH(CH3) (Ar), derived from acetic acid R = CH3 and benzoic acid R = C6H5, were prepared and characterized. The diastereo-isomers, differing in their 1H NMR spectra, were partly separated by fractional crystallization. After equilibration with respect to the labile Mo configuration the diastereoisomer ratio, a measure for the asymmetric induction from the chiral ligand on the formation of the two Mo configurations at equilibrium, was determined by 1H NMR integration. The asymmetric induction is very high for Ar = o-tolyl [76% (R = C6H3) and 84% (R = C6H5)] compared to Ar = phenyl [48% (R = CH3) and 56% (R = C6H5)] and Ar = m-and p-tolyl [52 and 44% (R = CH3)]. The (CO)3Cr complexed phenyl substituent with only 10% asymmetric induction does not show the β-phenyl effect, a weak attraction between aryl groups in β-position to the metal atom and the MC5H5 moiety.