Optical Resolution and Racemization of Tris(acetylacetonato)germanium(IV) in Organic Solvents

The tris(acetylacetonato)germanium(IV) has been resolved by the crystallization of its hydrogen-R,R-di-benzoyltartrate in a mixture of acetonitrile, ethanol, and water. The racemization kinetics of perchlorate of the Δ-enantiomer has been studied in 1,1,2,2-tetrachloroethane (TCE), nitromethane, acetonitrile (AN), and N,N-dimethylformamide, the activation enthalpies (ΔH/kacl· mol−1) and the activation entropies (ΔS/cal· K −1 mol−1) being 27.9, 26.6, 24.3, and 23.3, and +3.7, −1.1, −4.4, and −5.0, respectively. The ligand isotopic exchange is much slower than the racemization under similar conditions. Consideration of acid (in TCE) and base (in AN) catalysis, influence of ionic strength and solvent effect suggests an intra-molecular mechanism via an intermediate in which one of the ligands is in unidentate state.