N-SALICYLIDENEAMINO ACIDATE COMPLEXES OF OXOVANADIUM(IV) .1. CRYSTAL AND MOLECULAR-STRUCTURES AND SPECTROSCOPIC PROPERTIES

The complex [VO(salgly)(H2O)] 1 dissolved in pyridine (py) to form bro wn [VO(salgly)(py)(2)] 2 (salgly = N-salicylideneglycinate). A brown c omplex [VO(sal-L-ala)(bipy)] 3 precipitated on adding 2.2'-bipyridine (bipy) to [VO(sal-L-ala)(H2O)] 4 (sal-L-ala = N-salicylidene-L-alanina te) in methanol. The structures of 2 and 3 have been determined by X-r ay diffraction analysis. In both the tridentate Schiff-base ligands oc cupy equatorial positions and the two heterocyclic nitrogen atoms of p y or bipy co-ordinate in equatorial and axial positions, completing an octahedral geometry around the vanadium. The circular dichroism spect ra of 3 dispersed in Nujol and in methanolic solutions are very simila r. This finding together with EPR and thin-layer chromatographic exper iments suggests that 3 is relatively stable to hydrolysis and that its structures in the solid state and solution are similar. Complex 2 and [VO(sal-L-ala) (py)(n)] are not as stable to hydrolysis as 3 and a so lid formulated as [VO(salgly)(py) (H2O)] was als isolated.