OPTICALLY-ACTIVE TRANSITION-METAL COMPLEXES .105. FACIAL AND MERIDIONAL CHROMIUMCARBONYLPHOSPHINE COMPLEXES

The optically active, facial complex Cr(CO)3(PP'P'') (1) with the tridentade ligand PP'P'' = (R)-(+)-1,2,4-tris(diphenyl-phosphino)butane has been synthesized and characterized. The complex Cr(CO)3(PP')P'' (PP' = (R)-(+)-prophos, P'' = PMe2Ph) forms two pairs of diastereomers, facial (3, 4) and meridional (5, 6), respectively, that can be separated by preparative column chromatography. Surprisingly, the CD spectra of Cr(CO)3(PP'P'') (1) and the facial diastereomer of Cr(CO)3(PP')P'' (3), which have the same configuration at the Cr atom, are dissimilar. The meridional configuration of the two isomers 5 and 6 of Cr(CO)3(PP')PMe2Ph is supported by the P-31 and H-1 NMR spectra of the optically inactive complex Cr(CO)3(PP')P'' (PP' = 1-[di(4-methoxyphenyl)phosphino]-2-(diphenylphosphino)ethane P'' = PMePh2), which forms the meridional isomers 9 and 10.