The speciation of homochiral and heterochiral diastereomers of homoleptic cobalt(II) and zinc(II) PyBox complexes.

Homochiral [M(( R )- L R ) 2 ] 2+ and heterochiral [M(( R )- L R )(( S )- L R )] 2+ isomers of [Zn( L Ph ) 2 ][BF 4 ] 2 , [Zn( L i Pr ) 2 ][BF 4 ] 2 , [Co( L Ph ) 2 ][BF 4 ] 2 , and [Co( L i Pr ) 2 ][BF 4 ] 2 ( L Ph  = 2,6- bis (4-phenyloxazolinyl)pyridine; L i Pr  = 2,6- bis (4- iso propyloxazolinyl)pyridine) have been prepared and characterised. Six of the eight compounds were crystallographically characterised, showing that steric repulsions between ligand substituents lead to more distorted coordination geometries in the homochiral isomers, especially in the L i Pr complexes. Heterochiral [M(( R )- L i Pr )(( S )- L i Pr )] 2+ (M = Zn or Co) undergoes partial racemisation in CD 3 CN through ligand redistribution reactions, whereas [M(( R )- L Ph )(( S )- L Ph )] 2+ does not (in agreement with previous reports). This may be a consequence of intramolecular π … π -interactions in [M(( R )- L Ph )(( S )- L Ph )] 2+ , whereby each pyridyl group is sandwiched between two phenyl substituents from the other L Ph ligand. These π … π -interactions are disrupted in homochiral [M(( R )- L R ) 2 ] 2+ , owing to the aforementioned steric clash between phenyl substituents in that isomer. [ABSTRACT FROM AUTHOR]