The absolute configurations of two optically active iron complexes, (+)578-CpFe(C0)(PPh3)(CH20-menthyl) (1) and ( + )578-CpFe(CO)(PPh3)(CFj2COO-menthyl) (2), have been determined by single-crystal X-ray diffraction methods and have been correlated with their circular dichroism spectra. The configuration of 1 is S and that of 2 is (based on the sequencing rules proposed recently by Stanley and Baird). Anomalous dispersion effects were used to elucidate the absolute configuration of 1, while that of 2 was determined using the (-)-menthyl group as a reference. From these results, the absolute configurations of a large number of complexes of the type CpFe(CO)(PPh3)(X) can be deduced and compared to their CD spectra [X = Br, I, Me, Et, zi-Pr, /-Bu, CH2-c-C3H5, CH2C1, CH2Br, CH21, CH2Ph, C(0)Me, S(0)2R, CH2S(0)20(menthyl), ( 2-C2H4)+BF4~]. It is concluded that the maxima found at the 300-350and 350-450-nm regions of the CD spectra can serve as a reliable indicator of the absolute configuration at iron, provided that the X groups are not too dissimilar. Crystal details: l-S crystallizes in space group P 2\ (monoclinic) with a = 10.882(3) A, b = 11.054 (4) Á, c = 13.664 (4) Á, ß = 102.66 (2)°,
Mittels Einkristallröntgendiffraktionsanalyse und vergleichen den Untersuchungen ihre CD‐Spektren werden die absoluten Konfigurationen der beiden optisch aktiven Fe‐ Komplexe (I) bestimmt.
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