Vanadium(V) complexes of mandelic acid
New vanadium complexes of mandelic acid (NMe4)4[V2O4((R)-mand)2][V2O4((S)-mand)2] (1), (NMe4)2[V2O4((S)-mand)2]·H2O (2), (NEt4)2[V2O4((S)-mand)2]·H2O (3), (PPh4)2[V2O4((R)-mand)((S)-mand)]·2H3CCOCH3·2H2O (4), and (NH4)2.5(NEt4)0.5[V3O7((R)-mand)((S)-mand)]·2H2O (5) (mand2− = mandelato ligand) have been synthesized and characterized by single crystal X-ray diffraction and FT-IR spectroscopy. The band assignment in the IR spectra was corroborated by DFT calculations. While the structures of 1–4 comprise the expected dinuclear [V2O4(mand)2]2− (V2L2) anions, the structure of [V3O7((R)-mand)((S)-mand)]3− (V3L2) in 5 is unique and represents a new structural type in vanadium(V) chemistry. Solution studies of vanadate with mandelic acid by 51V NMR revealed the presence of two dominant species V2L2 and V3L2 in aqueous solutions and increasing fraction of V3L2 species at slightly acidic pH (pH ≈ 6).