Investigating the isolation and interconversion of two diastereoisomers in an octahedral system

Two diastereoisomers of bis(2-benzoylpyridine-O,N)dichloridonickel(II) have been isolated from the reactions of nickel(II) chloride hexahydrate and the organic ligand depending on the reaction solvent (ethanol, acetonitrile) used. DFT studies indicate that one of the isomers is more stable in both solvents, but nevertheless different diastereoisomers are crystallized from the two solvents. The two complexes represent the first pair of well characterized diastereoisomers in the coordination chemistry of 2-pyridyl ketones, providing a new example in the chemistry of octahedral complexes (A = a monodentate ligand, = an unsymmetrical bidentate chelate).