FACILE INTERCONVERSIONS BETWEEN DIASTEREOMERS OF CHLORO-BRIDGED PALLADIUM(II) DIMERS OF ORTHOMETALLATED (+ -)-DIMETHYL[1-(1-NAPHTHYL)ETHYL]AMINE/

The important chloro-bridged dipalladium(Il) resolving agents (RR)- an d cis-di-mu-chlorobis[1-[1-(dimethylamino)-ethyl]-2- naphthalenyl-C,N] dipalladium, (R,R)- and (S,S)-cis-1, undergo facile rearrangements int o unequal mixtures of cis and trans diastereomers upon dissolution in chloroform or dichloromethane, although concentration of the solution in each case affords in high yield the pure cis diastereomer of the di nuclear metal complex as the corresponding mono-solvate in a typical s econd-order asymmetric transformation. When equimolar solutions of(R,R )-cis- and (S,S)-cis-1-CH2Cl2 in dichloro-methane are mixed together, however, an equilibrium is rapidly established between the cis and tra ns diastereomers of the (R,R*)-(+/-) and (R*,S*) forms of 1 and from which solution configurationally homogeneous (R,S*)-trans-1-CH2Cl2 cr ystallizes in high yield by second-order asymmetric transformation. Th e crystal and molecular structures of (R,R)-cis-1-CH2Cl2 and (R,S*)-t rans-1-CH2Cl2 have been determined. The optical purities of the indivi dual enantiomers of (R,R*)-(+/-)-1-CH2Cl2 have been determined by rea ction with (1R,2S,5R)-menthyldiphenylphosphine or (1S, 2S, 5R)-neometh yldiphenylphosphine in chloroform-d(1) and analysis of the P-31(H-1) N MR spectra of the resulting solutions of the corresponding bridge-spli t palladium(II)-phosphine epimers. (C) 1997 Elsevier Science Ltd.