Biphenyl Tricarbonylchromium Complexes. Part 9: Syntheses, Chromatographic Resolutions and Chiralities of Mono and bis(Tricarbonylchromium)Complexes of Di- and Tetrasubstituted and Bridged Biphenyls

Article abstract of DOI:10.1007/BF00816342

Chiral title compounds have been resolved by medium pressure liquid chromatography (MPLC) on triacetylcellulose in ethanol.Whereas a quantative separation was achieved for 16 and 20, a recycling technique had to be applied to 1, 4, 6, 10 and 15 leading to a 100percent e.e. for 1, 6 and 15 and to ca. 60percent e.e. for 4 and 10.An unambiguous assignment of the chirality (+)-(R)_a-(S)_m for tricarbonylchromium-6,6'-dimethyl-diphenic acid dimethylester (4) was deduced both from the photochemical decomplexation to(-)-5 with the known chirality (R)_a (whose e.e. was determined by M PLC on triacetylcellulose) and by comparison of the 1H-n.m.r. spectra of 4 and 5 thereby proving the structure 4a for the former.Other chiralities both for mono and bis(tricarbonylchromium)biphenyl complexes were established by chemical correlations and comparison of the CD spectra with those of key compounds. - Keywords: Triacetylcellulose; Recycling technique; Enantiometric purity; Metallocene chirality; Conformation.