Photocatalytic deracemisation of cobalt(III) complexes with fourfold stereogenicity.

The deracemisation of fourfold stereogenic cobalt(III) diketonates with a chiral photocatalyst is described. With only 0.5 mol% menthyl Ru(bpy) 3 2+ photocatalyst, an enantiomeric enrichment of up to 88 : 12 e.r. was obtained for the major meridional diastereomers. Moreover, a distribution of configurationally stable diastereomers distinct from the thermodynamic ratio was observed upon reaching the photostationary state.