Diastereoselectivity of Octahedral Cobalt(II) Pybox Complexes

The cobalt(II) complexes prepared with a series of enantiopure ligands (1-3) containing the bis(oxazolinyl)pyridine unit have been studied. The ligands form high spin octahedral complexes as shown by the X-ray crystal structure of the homochiral complex [Co(R,R-1)(2)](ClO4)(2)(CH3CN)(3). The diastereoselectivity of complex formation has been studied: equimolar mixtures of RR and SS ligands show mixtures of homochiral and heterochiral complexes for 2 and 3, but the phenyl-substituted ligand 1 shows exclusive formation of the heterochiral species. This selectivity is correlated with structural and electronic properties of the complexes.