Octahedral metal centers with two or more chelating β-diketonate ligands are well-known to be chiral. Although a number of homometallic β-diketonates with polynuclear structures contain multiple octahedral chiral centers, no diastereomers have been observed in those systems. Even with the development of heterometallic diketonates as well as inclusion of additional non-octahedral chiral metal centers, there was still no diastereomers reported. By increasing the complexity of heterometallic complexes, a pentanuclear diketonate compounds were obtained, in which diastereomers were finally detected. In these mixed-valent, heteroleptic systems [MIIL3−Na−M'IIIL'3−Na−MIIL3], two diastereomers have been isolated and characterized separately. Metal centers chirality was determined by single crystal X-ray investigation. Since the diastereomers contain neighboring 3d transition metal atoms with close atomic numbers, masses, radii and the same oxidation state and coordination/ligand environment, a combination of investigative techniques that include synchrotron resonant diffraction, X-ray multiwavelength anomalous diffraction, X-ray fluorescence spectroscopy, and gas-phase DART mass spectrometry were employed to unambiguously validate the assignment of the 3d transition metal positions and their oxidation states.

Diastereomers in polynuclear heterometallic diketonate complexes

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