Thermal Isomerization of Fac-Tris(L-amino Acidato)chromium(III) in Solid State

The thermal isomerization of fac-Δ- and/or fac-Δ-tris-[Cr (AA) 3 ] in solid state, where AA stands for an L-amino acidato ligand (L-alaninato, L-norvalinato, L-norleucinato, L-valinato, L-leucinato and L-isoleucinato), was studied under an isothermal heating at 180 °C for 5 h. The isomerization behavior of those complexes was classified into two groups, though all the resulting products at equilibria were of facial configuration. In the case of [Cr(ala) 3 ], [Cr (norval) 3 ] and [Cr (norleu) 3 ], only fac-Δ-[Cr(AA) 3 ] was obtained irrespective of configurations of the starting complexes, while [Cr(val) 3 ], [Cr(ile) 3 ] and [Cr(leu) 3 ] gave mixtures of diastereoisomers on heating. By separating those products into each diastereoisomer, fac-Δ-[Cr(val) 3 ] and fac-Δ-[Cr(ile) 3 ], which had not been previously obtained, were prepared satisfactorily.