Syntheses and crystal structures of oxovanadium(IV) complexes with N,N′-ethylenebis(amino acids)

The oxovanadium(IV) complexes with N,N′-ethylenebis(amino acids) ([VO(XeX)(H2O)], where X=A ((S)-Ala), V ((S)-Val) and P ((S)-Pro)) are synthesized and characterized by X-ray analyses and IR spectra. The crystal structure analyses reveal that the geometry around the vanadium cation of each complex is distorted octahedral and is coordinated by a water molecule and the tetradentate N,N′-ethylenebis(amino acidate) anion with Δ-cis-α configuration, in which the water oxygen atom occupies equatorial coordination position and one of the two secondary or tertiary nitrogen atoms of each tetradendate ligand is bound trans to the vanadyl oxo moiety. The compilation of bond lengths for present and previous VO complexes containing nitrogen and oxygen donating ligands shows that the tertiary amine groups of PeP ligand elongate VN bonds. Comparison of the sum of the bond angles of three five-membered rings (one ethylenediamine ring and two amino acidate rings) indicates that the ring strain is mostly concentrated in the ethylenediamine ring and the strain of amino acidate ring lying in the equatorial plane of V(IV) ion is more pronounced than that in another amino acidate ring. The IR observations of the present complexes are well consistent with the crystallographic studies of them.