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

Racemic 2,2'-bis(pyridin-2-yl)-1,1'-binaphthalene (+/-)-6 was prepared in f our synthetic steps from 2-naphthol. Resolution of the novel atropisomeric ligand 6 was effected by repeated preparation, recrystallisation and then l iberation of the bis-tartrate salt (D and L). This affords both enantiomers of 6 (> 96% enantiomeric excess, ee) whose absolute configurations were as signed by CD. The ligand 6 is stable towards racemisation (Delta G double d agger(rac)> 167 kJ mol(-1)) and the structure was confirmed by single cryst al X-ray diffraction of the complex [ZnCl2(6)]. The structure and stereodyn amics 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 s tate by single crystal X-ray diffraction. Apparent stereodynamic processes of the allyl ligand, as detected in solution by NMR, are shown to arise fro m ligand 6 stereodynamics and exchange. The ligand 6 represents the first c ompound/building block for a series of enantiomerically pure N,N-ligands th at may be of utility in supramolecular co-ordination chemistry and in asymm etric catalysis.