Determination of the absolute configurations of the epimers of the P-chiral phosphine Ph2PCH2CH2P*Ph(L-(-)-menthyl) by use of two-dimensional NMR spectroscopy in combination with a palladium(II) "reporter complex"

Article abstract of DOI:10.1016/0022-328X(94)00033-9

The two epimers of the new P-chiral phosphine Ph2PCH2CH2P^*Ph(L-(-)-menthyl) (1-Rp and 1-Sp) were synthesized by treating Ph2PH with the diastereometrically pure forms of Ph(L-(-)-menthyl)CH=CH2)P.The palladium(II) complexes , 2-Rp, and , 2-Sp, were obtained by treating the corresponding bisphosphines with .Each of these complexes exists in the form of two regioisomers differing in the orientation of the chiral phosphine relative to the C-donor.Constraints from close interligand, intramolecular hydrogen-hydrogen contacts within three of these palladium complexes were detected by two-dimensional NOE spectroscopy, and were used to determine the absolute configurations at the chiral phosphorus centers in the Ph2PCH2CH2PPh(L-(-)-menthyl)isomers.The conformations of the two chelate rings in the more abundant of these isomers were also determined. Keywords: Chiral phosphine; Absolute configuration; Two-dimensional NMR; Palladium; Solution structure