Bis(phosphane oxide) adducts of Rh2(MTPA)4 - Kinetics and chirality discrimination

Abstract

The symmetrical bis(phosphane oxide) 1 and its chiral derivatives 2 and 3 form a variety of adduct species with the dirhodium complex [Rh-Rh] which can be identified by low-temperature 1H and 31P NMR spectroscopy by using varying [Rh-Rh]: ligand ratios. The asymmetric bis(phosphane oxide) 3 shows a distinct preference for binding through the Ph2P= O (P a) as compared to the tBu(Ph)P=O (Pb) functionality due to the bulky tert-butyl group. The chiral bis(phosphane oxides) 2 and 3 form complex mixtures of various adduct species. Nevertheless, it is possible to monitor enantiomeric compositions from various NMR signal duplications at 213 K and even at room temperature or slightly elevated temperatures. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.