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

Lookup NU author(s): Dr Simon Doherty, Dr Rakesh Rath, Dr Julian Knight

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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.


Publication metadata

Author(s): Doherty S, Newman CR, Rath RK, Van Den Berg J-A, Hardacre C, Nieuwenhuyzen M, Knight JG

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 2004

Volume: 23

Issue: 5

Pages: 1055-1064

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/om034289f

DOI: 10.1021/om034289f


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