Preparation and Circular Dichroism of Dichloro-(S)-2-(butylphenylphosphinomethyl)pyrrolidine-palladium(II)([PdCl2L]) and Its Related Complexes, and the Absolute Configuration of [PdCl2L] Determined by X-Ray Analysis

Abstract

Abstract (S)-2-(Butylphenylphosphinomethyl)pyrrolidine(L) was prepared from (S)-proline via four main reaction steps. A pair of diastereomers of the PdCl2L complex, the isomerism of which comes from chiral configuration of the phosphorus atom, crystallized in different forms (needle and block), which were separated by hand picking. The molecular structure and absolute configuration of one(block) of the dichloro complexes was determined by X-ray analysis. Crystallographic data are: P212121, Z=4, a=13.576(4), b=16.351(3), c=8.041(2) Å, and R=7.8% for 1659 reflections. The Pd atom has a distorted square planar coordination of four donor atoms. The Pd-Cl bond distance trans to Pd-P, 2.367 Å, is longer than that trans to Pd–N, 2.296 Å. The absolute configuration of the coordinated phosphorus atom was determined to be R by assuming S configuration for the asymmetric carbon atom of the aminophosphine. The corresponding diastereomers of the dibromo complex were also prepared from each diastereomer of the chloro complex. The circular dichroism spectra of these diastereomers were compared with one another and with those of other related complexes, and the vicinal effects due to the chiral phosphorus atoms in these complexes were examined.