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.
|Number of pages||10|
|Publication status||Published - 2000|
- (PI-ALLYL)PALLADIUM COMPLEXES