Ligand exchange and stereodynamics in the cationic palladium(II)-pi-allyl complex of 2,2 '-bis(pyridyl)-1,1 '-binaphthalene, a novel atropisomeric N,N-ligand

JPH Charmant, IA Fallis, NJ Hunt, GC Lloyd-Jones, M Murray, T Nowak

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Racemic 2,2'-bis(pyridin-2-yl)-1,1'-binaphthalene (+/-)-6 was prepared in four synthetic steps from 2-naphthol. Resolution of the novel atropisomeric ligand 6 was effected by repeated preparation, recrystallisation and then liberation of the bis-tartrate salt (D and L). This affords both enantiomers of 6 (> 96% enantiomeric excess, ee) whose absolute configurations were assigned by CD. The ligand 6 is stable towards racemisation (Delta G double dagger(rac)> 167 kJ mol(-1)) and the structure was confirmed by single crystal X-ray diffraction of the complex [ZnCl2(6)]. The structure and stereodynamics of the complex [Pd(eta(3)-C3H5)(6)][OTf] (OTf=O3SCF3) which comprises a C-2-symmetric ligand bound via Pd to a non-C-2-symmetric allyl fragment was studied in detail in solution by 1-D and 2-D H-1 NMR and in the solid state by single crystal X-ray diffraction. Apparent stereodynamic processes of the allyl ligand, as detected in solution by NMR, are shown to arise from ligand 6 stereodynamics and exchange. The ligand 6 represents the first compound/building block for a series of enantiomerically pure N,N-ligands that may be of utility in supramolecular co-ordination chemistry and in asymmetric catalysis.

Original languageEnglish
Pages (from-to)1723-1732
Number of pages10
JournalDalton Transactions
Issue number11
Publication statusPublished - 2000



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