Comparative study of diastereoisomer interconversion in chiral BINOL-ate and diamine platinum complexes of conformationally flexible NUPHOS diphosphines

Academic Article

Abstract

  • A thorough and detailed study of diastereointerconversion in the chiral platinum complexes [(NUPHOS)Pt{(S)-BINOL}] (3a-e) has been undertaken and compared with the results of a similar study with [(BIPHEP)Pt{(S)-BINOL}]. Rate data revealed that this process obeys first-order relaxation kinetics, and rate constants for conversion of the minor to the major diastereoisomer have been obtained. Eyring analysis of the data gave ΔH‡ and ΔS‡ values of 22-25 kcal mol-1 and -1 to -16 eu, respectively. In combination with computational analysis, these studies indicate that atropinversion most likely occurs via an on-metal pathway involving a planar seven-membered transition state. Substitution of (S)-BINOL for (S,S)-DPEN results in a marked reduction in the barrier to atropinversion; a ΔH‡ value of 17 kcal mol-1 has been determined for the conversion of δ-[(Ph4-NUPHOS)Pt{(S,S)-DPEN}]-Cl2 to λ-[(Ph4-NUPHOS)Pt{(S,S)-DPEN}]Cl2, which could indicate that an alternative mechanism operates.
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Doherty S; Newman CR; Rath RK; Van Den Berg JA; Hardacre C; Nieuwenhuyzen M; Knight JG
  • Start Page

  • 1055
  • End Page

  • 1064
  • Volume

  • 23
  • Issue

  • 5